# Homemade Tools >  Good advices for a newbie (threading tools lathe)

## rendoman

Hi!
I'm a newbie of this forum  :Smile: 
Some weeks ago i fixed my old lathe, changed bearings, restored a shaft for automatic, and buyed some gears for threading. Hardware store in Italy are similar to chinese store, same poor quality and common tools for Diyers sold at higher prices, the bigger is the shop the lower is the quality. Industrial suppliers have very good brands and tools, but they don't sell at single people, and if they sell the price is high as hell. At this time i have troubles finding used good tools. Surfing on internet i found on aliexpress some chinese indexable tool with insert, ( 40\50 $ one tool + 10 insert ) but i don't know if they are good or not.

I see in this forum some really interesting post of very skilled people, i'd like to ask some advice or tips and tricks for create internal (and maybe external) threading tools for lathe. I'm not too skilled in grinding tools, i'd like to create something sharps for threading aluminum and steel ( not inox ).

I post some photos of my little box with tools, i got lathe, cst milling machine, tube and plate bender , electric saw slow blade (sorry i don't know the eng name, in italian is "troncatrice a disco lento" with steel blade with short theets). transformer ac old welder and oxy-acetylene torch ( 40-500 lt/h and cutting torch )

Thanks in advance for an answer

Ps: my next project is to make a pair of aluminum horn similar tothe last photo, but bigger (130mm - 5" dia), i need threading the horn and the flange attached to driver.

Saluti
Stefano

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Paul Jones (Dec 3, 2015),

redearthbonsai (Jul 12, 2018)

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## Ed ke6bnl

I am not real machinist but bought my DRO through aliexpress and a nicely made threading tool with insert for the price of an insert. good service and good products. I will be doing more business with them

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## C-Bag

Hi Stefano, and welcome.

I'm new to threading on the lathe too, but there is a lot of folks on here like Paul and Marv who can help. 

Just to be clear, the units in picture #5 are audio tweeter horns or wave guides, correct? And you are wanting to make larger versions of these? Are the drivers you are wanting to thread into the horns threaded?

I personally learn a new process best when I have a project, just like yours. I would think your first step would be if you have threads on the driver to use a thread gauge to determine the thread pitch. Then check your lathe gears to see if you have the correct gears to make that pitch. There are lots of great videos on YouTube on threading. Sorry if you already know all of this.

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Paul Jones (Jan 5, 2016),

rendoman (Dec 4, 2015)

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## rendoman

Hi! thanks for advices!

The units in 5th picture are tractrix profile horn on an ex apt150 eminence driver. I didn't like the sound of the original constant directivity horn in my small room (5 x 5m) i tried different kind of profiles and wave guides on drivers 1" and 2", after my tests i found the tractrix profile maybe the best sounding at all for focus and detail (and for my taste).
I tried exponential, conical, multicell, iwata profile and some Others, i still prefer tractrix  :Big Grin:  conical and iwata not bad! In my opinion the best things to do is choose the right frequency range in which the driver gives the best, than project the horn smaller possible. 

I posted a couple of fresh photos of drivers, they have plane surface with 4 m6, i want to make a flange threaded and a bigger version of the 5th pic tractrix threaded too. I used this driver with different attachments for many years, although Rcf rate this drivers from 1K to 20khz i'm sure that using them in this range is a suicide  :Big Grin:  they start good at least up to 1,6khz (2khz is better) and end at 12khz. Using them before and after this range in my opinion is forcing. In Pa speaker with 2 or maybe 3 way with a woofer really extended that's the only choice. 
I don't know your ideas about spaker with fullrange or multiway system, i can summarize my experience and my taste in few points:

- high sensivity full range (single cone or whizzer, i want to try lowther alnico on my system) for voices and range from 100 up to 10k
- great improvement using subwoofers down to 250hz
- good setup with tweeter just for some more air

In my system maybe i don't need the 4th way, i got the range from 150hz to 15khz covered with the big horns up to 110db/w/m, but i love to see this massive aluminum horns  :Big Grin:  and i want to make some test

Your right, I think i have to setup a good steps program, the project is a bit complicated and i have no possibility to fail  :Sweating: 

Are you enthusiast of hi end audio?

ps: sorry, my english is bad as hell

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PJs (Dec 21, 2015)

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## C-Bag

Your English is a million times better than my non existent Italian  :Smile: 

In my youth I dabbled in hi end audio, but we are talking in the 70's. At that time there was what I think of as 2 schools of thought, hi efficiency JBL/Klipsh 2way horns with like around 75w RMS x2 amp. The camp I was in was the lo efficiency 2 way ESS Heil transformer line cabinet bi amp Dynaco 120 for teeters and Dynaco 400 for lows. I still own a set of EES's with Hafler pre and 220 amp. It cured me of the search. The Heils go from 1k to 22k. 

As an acoustic musician, it sounds the most like what those instruments sound like live to me. I don't have the large line transmission cabs, but if I could have any cab for lows to match with the Heils it would be the old Dynaco A-50 cabs. With a big amp like the 400 running it with a good electronic crossover they would go down to 20hz. We did it with a frequency generator. Sadly you don't see those around much, and the design was a tuned baffle design that I've not found any plans for or I'd try and replicate them. They we much smaller and musical than a line cab IMHO. By the totally impressive picture of your stereo (wow!) I would say you and I are also in different camps as I shy away from directional horn setups. I'm more into what we used to call the "bathtub of sound". 

I'm a mandolin player and mostly play Bluegrass, Irish fiddle tunes and some folk. So those genres and gypsy jazz is what I mostly listen to. I play in a couple of bands and when I think about it I was exposed to live sound PA's before I started to play an instrument. So dealing with PA is a whole other world. And most of the equipment is in the high efficiency camp. I use a set of gen 1 Mackie SRM450's(made in Italy!). I like the sound, they are a little heavy, but they just keep going. I toy with the idea of trying to build a set of PA cabs using the spare set of EES drivers I have.....but I'm lazy, and the Mackies are still going strong.

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Paul Jones (Mar 31, 2016),

PJs (Dec 21, 2015),

rendoman (Dec 21, 2015)

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## PJs

Welcome Stefano! Ambitious project but your system Rocks at least visually, just can't hear it from here!  :Wink:  

As for threading on the lathe, I am a novice but done some. I found with aluminum I prefer high speed steel tools and grind my own. If you have a fish tail they are easy to grind. The profiles are easily found on the net, basically 60º with no top relief and around a 7º side clearance angle. The key is to know what the root radius is and grind it appropriate for the thread you are cutting. For internal threading you can search the net to find various profiles depending on your project and depth (length) you need to cut based on square tooling stock. You can also make one from round bar and use round tool stock with a flat ground on one side, drilling a tight clearance hole for the stock and then use a set screw to hold it in place in the round bar.




> I tried exponential, conical, multicell, iwata profile and some Others, i still prefer tractrix conical and iwata not bad! In my opinion the best things to do is choose the right frequency range in which the driver gives the best, than project the horn smaller possible.



Very impressive on cutting the various profiles or did you just try them for your space? I would think that any time you add a horn, especially of the magnitude you are talking that it will be much more directional than the flat face style. Love to see where you take this based on your other horns!

C-Bag, you continually amaze me on the breadth of you knowledge. Aaaahhhh! ESS Heil AMT1, Sansui 1000, Nakamichi PA 7...Oh My, Yes! Still have my Sony PSX 7 with a Stanton 681EEE. Still love tubes for quality and richness. One day a set of MacIntosh's and modern Retro Heils to replace my Marantz and Monitor Audio set...(bucket list and lottery win)!

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C-Bag (Dec 21, 2015),

Paul Jones (Jan 5, 2016),

rendoman (Dec 21, 2015)

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## C-Bag

I'm glad you joined the party PJs and was helpful to Stefano. My ramble into my lo budget ancient hi fi days didn't do much to help his quest for audio nirvana :Smile: 

With your truly impressive background PJs do you think it's even necessary to have the guide thread onto the driver? Wouldn't a slightly tapered press fit with a set screw give as good acoustic coupling? Of course this would mean machining off the treads of the driver and then fitting the guide appropriately. But for my limited threading abilities this would be easier. 

In my mathematically impaired brain I've wondered if it was desirable to excite the guide, or to have it dead? Inquiring ears want to know....

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rendoman (Dec 21, 2015)

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## rendoman

Many thanks for the advices!  :Smile: 
In the days after xmas i think i'll try to make an internal threading tool from round bar. It's late to buy from aliexpress now, italian post office is like hell (one of 1000 bad services to people  :Flame:  ) if i buy now, i will receive in a month. I'm searching for a kit internal + external and insert 60° and 55° (i want to make some sort of reloading dies). I'm searching also for a fish tail, mission impossible here, i went to 5 specialized hardware store but nothing! i have to buy online.




> Very impressive on cutting the various profiles or did you just try them for your space? I would think that any time you add a horn, especially of the magnitude you are talking that it will be much more directional than the flat face style. Love to see where you take this based on your other horns!



I hope you'll excuse, my English is not good enough and i got some difficulty understanding, above all the last phrase  :Big Grin: 
I cut on lathe only the tractrix profile for tweeter ( 75mm dia) and now for driver (130mm dia), i built other profiles using paper mache, cement, plaster , steel and vtr ( i really hate resin, lot of dust everywhere and bad smell ). I tried some of these "prototype" in other system and room, i think the first of basic requirements is to have a good room, and at least 1.5/2m of distance from horn.

This type of horn is maybe the most directional you can choose, above all compared to traditional flat face. Someone hates horns, someone loves it... i think horns are a bit bastard :Big Grin:  If you listen a good horn system, well sounding, it's a pleasure. If you listen some bad approach not to point ... the listening can be difficult...

I experienced that worst thing are: choosing a wrong cutoff frequency, and not paying attention to seal well the horn with driver. As says C-bag the threading solution is maybe more for aestethic reasons than for practical use. As you can see i mark the hole for connecting the driver to the flange, but i'm not sure if it's better to make threading or a "simple" flange with 4 short m8 inox and a short "guide" between horn-flange-driver (1mm dept).
My threading problem is that if I fail , i throw the aluminum bar  :Roll Eyes (Sarcastic):  i fear this!

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C-Bag (Dec 22, 2015),

Jon (Dec 21, 2015),

Paul Jones (Mar 31, 2016),

PJs (Dec 22, 2015)

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## C-Bag

Stefano as we say in English, there's more than one way to skin a cat! You are doing what I tried to do when I was young. Take an idea and almost make it from the ground up. You are in the right place as that's what we do here! It also helps you have the time and resources to do it. 

I think all of us have to rely on the mail for special parts. I know I do. I'm lucky Los Angeles is only 200mi. away and I can get things sent here within a couple of days because there is very little here for machining supplies.

So on pic #2 you are gas welding aluminum horn? And you made the big horns in your other pictures? Are the different sections not just for esthetics? But to keep the horns from resonating or to help them resonate? That has always been the "bastard" for me with horns......they are so COMPLICATED! And my impression is the only way to balance the whole system is to have the same efficiency from top to bottom. And to compound all this the ear hears different frequencies differently. Wow, you have really got a complicated project here.

I would have a really hard time getting big pieces of aluminum like In your photos. If it's so hard to get, and press fit would do instead I'm curious why you still want to thread on the guide? I'm not criticizing, I truly am curious about all this stuff.

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## rendoman

In pic 2 it's steel 8\10, even my big horn are made from steel. the reason is cost  :Wink:  here aluminum plate and bar are difficult to find and they sold at very high prices ( 40km the nearer shop, 8e \ kg ). I tried to weld a 6\10mm alu plate with oxy-acet and a special flux with criolite, i got the recipe in my manual, but ingredients are not easy to find. really expensive flux and delicate material, when flux is good quantity and quality it's a fraction of second and it makes huge holes, when flux is poor or not in quantity alu makes White oxide cover... I tried because i want to build to my 2 little bikes alu gas tank, the steel one ugly i made, not treated with tankerite or similar is making some rust.

As you say the different sections are not just for esthetics in my big horn, i made 2 horns loaded by one driver, in few words the big and long part cover from 100 to 350\400 hz and the small upper horn cover from 350 to up frequency. You're right! i choose steel and the "floating" Anchorage with silentblock to help them resonate more than a cement type horn. It was a gamble, i bet that above all in lower fq this can help, the mix steel + body shutz + cork gives good performance .
In this days i should receive a microphone for testing the speaker (ecm8000 behringer, with Scarlett 2i2 sound card and dcx 2496 processor), i hope i can do some good measures and adjust the system!


you're right about mixing different kind of speaker and horns, it's not so easy making passive crossovers, but it's not impossibile. With a bit of luck the differences in efficency can be solved using an L-pad resistor or a pot to match other speakers. The big problem in my opinion is the prices of components for making good passive xovers, if you want to make a first order filter bw type for a tweeter, a simple (but good) cap like mundorf makes excellent work with few bucks, but when you have to buy different huge inductors and capacitors for trying some lower (150 to 500hz) cuttoff fq the situation becomes hard, and even harder trying different order of xover... I thinked lot of time, but at the end i decided to buy an active crossover with 3 stereo channel. this dcx 2496 is cheap compared to other hi end filters, it's pro audio, but it sounds good and above all you can change type of filter, delay, cutoff, offset, eq and Others parameters in real time. cons you have to give it one amplifiers for each channel ... but it's not a big problem 

now i have to go out, after i try to do a simple image of the flange. the last 2 pics alu plate welded with flux and not grinded. i think with some practice i can weld 1,5mm for gas tank

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## C-Bag

ooooooh, to much fun!!! So many things going on here. Playing with the materials of the horns is very interesting. But like I learned when trying to mix one of our albums it's VERY easy to get lost. My old friend of almost 50yrs who we went through the audio stuff together and he taught me how to play guitar, is now a pro live sound audio engineer. He is in another world to me but he can dumb it down enough for me to understand some concepts.

Several of the major ones is just like you have mentioned many times is crossover points and resonance peaks. And then the real gorilla in the room time alignment. This is why all the pros went to active crossovers years ago. Now they have moved on and everything is computer controlled in the amps and networked into the engineers laptop along with the digital mixers. 

Through him I bought an old copy of SMAARTLive, the program the pro's use to analyze the rig. Everything from time align to realtime frequency analysis and a ton of other stuff that makes my head swim. I used it to set the eq on my live PA by hooking it through a mobilepre into my laptop and it would show me the peaks that were causing feedback and I used a 31 band eq to tame the peaks/kill the feedback. Worked ok, but it was a little like using a hammer to kill flys. 

Then along came a guy who was looking to sell a dbx DriveRack 260. Amazing piece of kit. Crossover, realtime analyzer, compressor, notch filter, parametric eq, 31 band eq, feedback buster, delay and auto eq, all in one rack space and has a plug to jack directly into the laptop where you can configure and daisy chain all these things any way you want, right on the laptop. Their bottom of the pro line unit. Now obsolete with my new line6 m20D digital mixer.

I mention all of this because, bravo! You are going in the right direction with analysis. But I hope you know you are in for even more complication  :Smile: 

My current upgrade dream is to make some new speaker cabs using my spare set off ESS drivers in a 2x10" modified line transmission cab with another Hafler amp for biamp and use the 260 and SMAARTLIVE to tune and align the system.

I too am working with gas welding aluminum. There is a guy here who teaches and sells all the stuff. Not easy or cheap, but very satisfying and another thing I want to have time to do. Love the stuff with your motor cycle....or do I see motorcycle frame with a scooter drive? Always thought that made more sense, lower center of gravity and they certainly have enough HP to get me in trouble.

I'm more low tech these days, in love with my ICE recumbent tadpole trike. My dream is to build a aluminum bodied velomobile...maybe even electric assist. But I have more dreams than I have time left  :Frown:

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PJs (Dec 22, 2015),

rendoman (Dec 22, 2015)

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## PJs

A lot going on here but I'll try to stay on point with the sound stuff as best I can.

First I believe you are right about the crossover being critical and think that going with an active is the best approach to cover all the variables in the horn design.

Coupling: Personally I think the threaded approach gives Better Coupling because of the continuous contact throughout the threaded length (quality 2A/B or 3A/B threads). With a tapered press or slip fit and (a) set screw(s) you will likely create distortions in the material, effecting the resonance of the cone as well as the direct coupling to the driver. I've never used Loctite products with this type of coupling but would probably try them in moderation to insure they don't come loose from vibration. Heat may be another factor, which the AL will help with.

Sound Mapping: The only way to achieve what you are trying to do IMHO. I have the EMC8000 mic and used it extensively to 3D map the coupling of my transducers to the sound table I designed a few years ago. I used spectral analysis software to capture all the data from the 3D grid map I created to measure everything. Because I was measuring within about 2' of the table the EMC8000 worked fine and is a great mic for those distances. However it is relatively directional like a shotgun mic. A room is another story because of the shape, variable densities of it, and above all the reflectivity of all of that. For speakers it's great!

Horns: I don't have much wherewithal around their design and implementation, but it's still Physics. Marv would be much better suited to help on this than me! 

The basic principles of sound transmission are: Frequency, Amplitude, Resonance, Harmonics, and speed of transmission based on the density of the medium. In this case a sound transducer that has all of these characteristics already, which will be coupled to a directional amplifier/modifier (horn)...which is why I was so impressed with your other shop made horns which fit Your Space and Tastes of quality!! To me the key is the shape and density of the material you are coupling to the transducer. Aluminum has a sound transmission speed of 3100-6400m/s depending on the type (density), whether its cast, rolled or extruded, etc. If you apply that to the Lambda(wavelength)=Velocity/frequency formula it will give you some "Basic" starting point for your guide and _if_ you are going in the right direction but won't cover the shape...much more complex. The diameters (ID/OD), will effect the sound coupling and frequency response curves and wall thickness can effect harmonics and ringing. The shape of the internal cone will more control the wave propagation and directionality. 

Sound has always been fascinating to me and partly why I built my sound table and HAWK delivery system. Whether it be listening, meditative or healing, I have a Strong Sense that Edgar Cayce was right with his point that "Sound will be the medicine of the Future".

Here is a picture of my HAWKs system. Note in the middle of the rack is an HP, 4 channel signal generation that works from DC to 600Khz and the ART SLA-4 amp at the bottom. The other pic is in our clinic (now closed) and shows the Korg attached...one of many delivery systems including 5.1 Surround headset driven optically.

 

It's now in storage and may donate it to the VA one of these days...when I'm ready to let go of it.

Thanks Stefano for starting this thread, I'm impressed and intrigued...look forward to what you come up with and how you did it!!

C-Bag, honestly I'm not sure how to answer you question of Excite or Dead, sound will permeate the material at some level and travel the path of least resistance...even a port's edges will vibrate as the sound travels through them. Again I'm a relative novice to some of this you guys are talking about...

Till Then, ~~~> ~PJ

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C-Bag (Dec 22, 2015),

rendoman (Dec 22, 2015)

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## rendoman

I'm impressed! I'm lucky to have found some audio fans (and pro) so prepared! 
for now i wish you a merry xmas! 
i got two short question for curiosity:

- some times ago i see a recumbent bike (sport road type), in your opinion it's so fast compared to a normal cycle?

- i see some really nice electronics for medicine use, what kind of diseases can be approached with sound?

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## C-Bag

I think you are talking about recumbent bicycles, so yes we are once again in different camps  :Smile:  I used to have an Italian 10sp bicycle that rode a lot. I always felt like it was a torture machine that I want to go as fast as I could so I could get off the damned thing. My hands and wrists always ached and were a sleep and I couldn't sit down for a week. Now I don't care how fast I go, it's all about enjoying the ride, the day, the trail and being outside in one of the most beautiful places on the planet. This is like what I have:

Recumbent Trikes - ICE - Adventure

I bought my wife one too. I would like to build something like this except pedal powered, not gas.

Decopod Tri-Pod - an art deco aluminum bodied scooter from Randy Grubb

Like my idol Howlin' Wolf said in a song, I'm built for comfort, not speed  :Smile:

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PJs (Dec 23, 2015)

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## PJs

Happy Holidays to all!!

Stefano: Without getting into a whole dissertation here I believe it needs a whole lot more R&D but we already have ultrasonics for soft tissue regeneration, sonics for gall stones, and a myriad of others actually being used by western style medicines. My system starts with the Mind and works with known frequencies and other systems for various things, but initially developed for myself after a bad motorcycle accident. I had seen a white paper several years earlier (10 year study) on the effects of low frequency for healing bone and soft tissue in joints. Frequencies between 20-40hz actually healed fractures 40% faster than conventional methods! Basically 30 minutes on my table and with the other systems built into it, I didn't hurt for a week! So I took it to the clinical level to help others and to generate further study. Personally I believe Royal Rife was on to something back in the day but like many things was squashed by greed and never fully studied and developed. I'd love to develop a hand held system similar to the ultrasonics used today...just not sure I have enough giddy-up nor Duckets (R&D ain't cheap) to "Get R Done" anymore.

C-Bag...I hear you about the comfort, but think my son and I are going to attempt a Drift Trike this year...maybe 2! The ICE mobiles look way comfortable!! Love the Decopod...too cool to Rule! More my style was his B702 though!! Oh My a Bugatti style with a 702Cu.In. V12...oh my...HO, HO, HO, I could deliver some presents in that! ~PJ

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## rendoman

small update  :Smile:  first step of flange, i take the simple way 
it would be a pleasure if he did not so much cold , my garage is frozen!

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kbalch (Dec 30, 2015),

PJs (Dec 29, 2015)

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## C-Bag

> small update  first step of flange, i take the simple way 
> it would be a pleasure if he did not so much cold , my garage is frozen!



Good pix. So "simple way" is not threaded onto driver? Bolted?

BTW, my garage is frozen too. I'm waiting for it to warm up so I can ride my trike down to the Post Office. That's my main use of it. Only 5mi. roundtrip, but all hills. 190' height gain and then down to the PO, then the same climb up and down back to my house. Down to 26 minutes roundtrip. Good for my truck( no short trip) and good for my waist and heart.  :Smile:

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PJs (Dec 29, 2015),

rendoman (Dec 29, 2015)

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## PJs

Thanks for the update pics Stefano. I hear both of you on the cold shop...mine was 45º F yesterday.

Looks like you made a mic holder also for your new EMC8000?

Curios what the depth of the cone will be based on the 1k-20k response on the driver? Is it some exact multiple of the wavelengths (1/_f_) of that frequency range (.0001 to .00005) to achieve some sort of resonance in the cone? With the exit port being 1.000" it seems you have the opportunity to tune the range a bit with the depth of the cone and of course the shape.

This all has me quite intrigued and really looking forward to how it all works out. Think I'll do some research on horn design!! 

Thanks again! ~PJ

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C-Bag (Dec 29, 2015),

rendoman (Dec 29, 2015)

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## C-Bag

> Curios what the depth of the cone will be based on the 1k-20k response on the driver? Is it some exact multiple of the wavelengths (1/_f_) of that frequency range (.0001 to .00005) to achieve some sort of resonance in the cone? With the exit port being 1.000" it seems you have the opportunity to tune the range a bit with the depth of the cone and of course the shape.



WOW, who was that masked man!?!?!? 

 :Bow: 

you go Wiz!

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PJs (Dec 30, 2015)

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## rendoman

many thanks!

good physical activity is healty for the body! hope that the temperature raise fast  :Smile:  ... here we'll have the next 2 months colder  :Frown: 

the range 1k-20khz is the "recommended" by rcf, in my opinion this driver sound good from at least 1500\2000hz to 10000hz, no more. under 1,5k and over 10k in my opinion it sounds bad and not so loud. I post a couple of pic of datasheet of the "new type" with neodimium magnet, i had a paper of fq response of my ferrite driver, it has 108db\w\m (1less than neod) and a bit more range up to 10khz. In my opinion it needs courage to claim the driver usable from 1 to 20k ... but the component is intended for pro audio... than...

you're right, there is some "tuning" opportunity. In my big horn i tried to settle both front and rear chamber for working togheter, basically not only the dept but the volume. Horn is an "air trasformer", unfortunately i have to find my old papers where i wrote the formulas, i got weak memory  :Big Grin: . I remember that a front chamber (not compression) introduce a high pass filter, but in this case it's not our problem 
Here we got a pre-tuned solid compression chamber that is the back of the driver, and we don't need to add a filter before the throat. With this kind of horn in my opinion only shape, cut-off and material are importants.
I tried some really ugly horns in plaster and cement, really bad internal surface as you can see, they sound good! I think that the real "tuning" is choosing the right cut-off frequency of the horn during design, not too low or the high freq will be cut, not too high or lowest freq of driver will be cut ... 

...in few words, for this horn, we have to choose the cutoff with head (and shape for the right use). imho only bass horns have narrow range of fq (mine big are 150-350hz realistic) horns up to 1khz have less issues

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PJs (Dec 30, 2015)

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## PJs

This thread just got my thinking cap on...no cape or mask, C-Bag but thanks for your kindness!!  :Embarrassed:   :Bow: 

Stefano: I downloaded the HF94 spec sheet which goes back to my question above about the total depth of the horn. The HF94 is 135mm which leads me to believe that you will add another piece to the flange above. ?? I would think the length is quite important to minimize the drop in pressure/db and maintain the dispersal and _f_ response. This makes sense as the dispersion curves for the HF94 are _quite good_ at 2, 4 & 8k and match the driver output well. Also agree  :Head Scratch:  they are hard pressed to prove the 20khz top end with a 10db drop off after 10k!!

What was interesting to me about the HF94 in the cross section view is the radial transition just above (no dimensions) exit port. I would imagine this straight section is part of the air motion chambering you speak of to increase the pressure into the actual cone. My hit is it is a tuned resonance chamber 1"ID x X"length (1/_f_ function) to achieve greater pressure prior to the cone. 

This is where I am at a bit of a loss to calculate the dimensions based on a range of frequencies. The driver curves above have a nice little rise at about 2500hz and may be a good number to shoot for cut off?? This might give you the power/pressure point to get it out through the cone and minimize losses?? It might also be good to include the pre-chamber dimensions (diaphragm to exit point) in the calcs because it has good/solid/3D pre-chambering and will probably be modified by the additional coupling, at least to the cone transition. What is the _f_ range you are shooting for over all?

Seem to be drooling here...Thanks! ~¿@  :Beer: 

PJ

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C-Bag (Jan 1, 2016),

rendoman (Dec 30, 2015)

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## rendoman

PJ you're right! that's only the flange, i have to made the real horn from the big round bar of 130mm dia.
Lenght is really important in the main horn profile, imho it's not so important adding a straight short cylindrical flange of the same dimensions of driver exit, but it's good only for diaphragm driver type). conversely adding short cyl after a cone makes differences. with cone the throat area of the horn is generally smaller than the the area of the cone, that's normal in order to obtain more pressure at mouth.
interesting point of view! you see good the range of the driver is between 2k-10k,impedence is not so high in 1k, but not so low.... imho for a PA speaker is good, for home ... eh! 
If we have to make an horn for a driver, it should have lower cutoff freq, for exemple: rcf from 1 to 20k, mid horn cutoff should be 800 or 700hz. 

I remember someone modified in the past the rear chamber of some driver, maybe to obtain a bit more bass. I always knew that after a driver starts a simple horn  :Smile:  , and no additional chambers needed.
i'm a self-taught, for sure I havnt the truth in my hand, the only thing i can do is reading, getting some formulas and making experiments 

at the moment the flange has only a 10mm hole for locking on the milling machine, i left 15mm dia, when i will be near to complete the horn i will add the flange and i will fillet the 2 parts together.

the project in the first pic is old, i made i think 3 years ago. the profile is the same.
The bad thing is that i'm learning to do things... i make one mistake after another  :Flame:   :Wink:

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C-Bag (Jan 1, 2016),

kbalch (Dec 31, 2015),

PJs (Dec 31, 2015)

----------


## rendoman

I think i need some new inserts... or have to learn to grind very sharp blade for alu...
... the part begins to take shape!

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C-Bag (Jan 1, 2016),

kbalch (Jan 2, 2016),

PJs (Jan 1, 2016)

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## PJs

Looking Real Good Stefano!! Pretty impressive lathe and horizontal mill you have. What are the models? 

Sorry I hadn't answered your previous post as I have been busy with some research on horn design. Found some interesting stuff out there. Better to keep my mouth shut when I was up to my ears in it!  :Lol: 

Martin King has some pretty impressive write ups with formulas and serious math, particularly on front loaded horn design and theory. There was more out there I found but this suited my liking for learning.

From what I gleaned from his front loaded horn paper it seems to me the that the length of the 1" exit channel does have an impact on the frequency range and SPL...although I read it quickly and may have misinterpreted his meaning¿

As for the _f_c it seems to me that it would be better to be just below the flat part of the curve...1.7k~2k maybe, to be able to keep just what you want. You could also add another filter at say12K to keep all the mids clean and within the capability of the driver. What made you choose the 7-800 range for _f_c?

Thanks for sharing your build with us!! ~PJ

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C-Bag (Jan 1, 2016),

rendoman (Jan 3, 2016)

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## C-Bag

Interesting stuff. 

I would like to see details how the inner contour of the horn is done to match the print and to make them both the same. You guys have left me in the dust so I will continue from the peanut gallery.

 :Popcorn:

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PJs (Jan 5, 2016),

rendoman (Jan 3, 2016)

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## rendoman

Hi
The mill is a type zero of CST, it's a factory 30km away from my home town. I found some years ago a Kondia (Bridgeport style) but too heavy, the shipping was a disaster due to my narrow Street... I changed the water pump and the main engine, from 1hp dahlander 3phase 380 to 2hp 230v monophase and new bearings.

The lathe i think is an old Grazioli fortuna (maybe 150 model), i say that because i see a close lathe with this name in the metal plate. No marks at all, outside and inside. I think it's a transition model between old lathe with leather belt and curvy leg base and "modern" trapezoidal belt. It's equipped with bronze brush, 3 gears main shaft and 4 gears for automatic ( longitudinal and transverse). 3cv- 2.2kw engine


CST snc - ZERO

CST snc - ZERO - caratteristiche

i can't remember where i read to setup freq cutoff 100hz (from 100 to 200) lower the starting frequency of the speaker, one things i see is that the choice of cutoff can really make the difference in range. for exemple, the big horn of my speaker should have 80hz cutoff, this horn in my opinion can be used from 150hz and the upper limit is between 350 and 400hz , basically not only due to cutoff but to a coefficient that rules range and efficency. 
more the frequency, less the problems. up to 1000hz cutoff horns are tiny and "similar". imho problems are under 1000hz, for example my rcf driver with old 4\500hz cutoff sounded strange, not extendend, not focused, same material but smaller 800hz made great difference!

I'm searching for an old site with a beautiful java tractrix and hyperbolic calculator, fullrange single driver site (maybe it changed name, maybe it doesn't exist anymore). good theory with formulas, exemple, tqwp, horn and project with lowther and a large number of drivers... 
i found this site, it's not like the original... 

Site Browser

I have to search 2 pdf with a good calculation, maybe too specific and hard to read, but useful... i hope i'll find!

... and the inner contour... a big problem... i have to do by hand  :Big Grin:  ... a template Always near the cylinder, light movements, and i suppose as i did for the last small horn: rasp, file and huge sand paper work... and a lot of patience  :Evil:

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PJs (Jan 3, 2016)

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## rendoman

as usual i post the daily updates  :Smile:  
I tried building an internal tool, i got a good one Seco, but at the moment i have only one side of insert good and the tool is not long enough. I got some 100 of romboid inserts, i'm not sure i've done a good job, Tomorrow i will try on the horn cylinder.

Got a question: i tried a blue ink for making marks on alu, but it makes a mess and it dissolves in few time. I saw in some youtube video (unfortunately i can't remember the link) a sort of purple glossy enamel, really thin that marks really well the metal, do you know the name of this special ink?

I'm making cylindrical steps, then i will use the angle on turret for doing the profile, hope i will not have to use many sandpaper!

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C-Bag (Jan 3, 2016),

PJs (Jan 5, 2016)

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## C-Bag

Looking good. :Thumbs Up: 

The stuff I've always used for layout is called Prussian Blue or Dykem steel blue. There's different types. The kind you want comes in a small plastic jar with a brush attached to the inside of the top. You brush it on and it dries really fast. If I understand what you are trying to do, I would use the Prussian Blue in one of the steps in the contour so you can use it like what I would call a witness line as you smooth horn to the final contour. That sounds like a LOT of work.

These is also Prussian blue that a kind of blue grease that comes in a tube. It's wonderful for finding high and low spots in precision machining. I used it when I used to do valve jobs on the old air cooled VW's to check valve seat concentricity. And also scraping metal to achieve true flat surface. It's easy to tell where high and low spots are by how light or dark the blue is.

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Paul Jones (Mar 31, 2016),

PJs (Jan 5, 2016),

rendoman (Jan 4, 2016)

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## PJs

Thanks for the info Stefano! Both mill and lathe look pretty substantial and good specs on the mill.

I took a look at the "Site Browser" site and seemed pretty good. I found the last paragraph of the first link interesting.

"For midrange and tweeter horns, many of the 
tractrix horn advantages are lost if the horn curve is terminated before the 
full, right-angle turn is reached. Unwanted edge diffractions would be created 
by the sharp edges of such a mouth. Thus no provision is made for the reduction 
of circular cross-section horns." 

The formulas there looked to be valid and could probably be done in Excel/spreadsheet, but it still comes back to that _f_c and in the case of a midrange the wavelength is very short (800hz = .0013) so I would assume it needs to be multiples instead of fractional...or just tiny.  :Stick Out Tongue:  Assumptions have a way of biting me back though~ @¿@ ...Thoughts?

The boring bar looks pretty good although those inserts don't seem to have a rake to them and may cause a bit of issue. Look forward to seeing how it works...think I might try it on something other than your part, first. ~¿@ Have you thought of maybe using a Graver to take off the tops of your steps? The depth may be a bit tricky to hold onto and need a rest to reach in there.

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C-Bag (Jan 5, 2016)

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## C-Bag

> "For midrange and tweeter horns, many of the 
> tractrix horn advantages are lost if the horn curve is terminated before the 
> full, right-angle turn is reached. Unwanted edge diffractions would be created 
> by the sharp edges of such a mouth. Thus no provision is made for the reduction 
> of circular cross-section horns."



(way back at the back of the peanut gallery) So does this mean there's going to have to be a major redo in the outer edge of the horn?

----------


## rendoman

Thanks for advices!
here in my area the best advice given in metal shop is : use a pen  :Wink: 
I want to use this prussian blue for layout, i thinked to use as witness line, but it's hard. i create a simple steel template with 6\10, but the finishing after tool isn't good, and maybe it's not necessary to copy so close to perfection the line. I used angled turret, and then files by hand, searching to copy the profile. Not a good job, not simple and very long... if you have some better ideas i have to do another one of this ...
I tired the boring bar... not to excellent, the perpendicular insert cut better, but there is something wrong in angles. with long arm (12cm) it vibrates like a dildo of sasha grey  :Lol: , very poor finishing, but good for cutting lot of alu. with short arm (6cm) no great vibrations, better cut, poor finishing. i tried to cut 2mm each time at dia, maybe too much. 
Strange thing, i used a Seco boring with triangular insert (Tomorrow i'll take a pic), got some problem with finishing with angled turret, maybe something to setup (gib?).

I got another little problem, protractor engraved under turret is semi-erased as you can see, some good and easy way for engraving a new one? yes, this lathe is pretty old and used.

You're right, when i studied for the tweeter horn i read that the final edge should be sharp. i left the first pair of horns with cm more than designed for trying the "round" final edge. if something didn't go well i might change the final edge easily. At listening even with round edge are not bad. now i got microphone , for sure i can make 
measures and then try the correct profile.
with this new horns i followed different path, i got alu in right diameter for the profile, no more cm to use, i can only cut some thents for finishing, as you can see the exit angle is sharp.

formulas... i think the Excel sheet is good, there is a coefficient from 1 to 8 in calculations that is used for lowering dimension of horn in order to create "bass" horn positionable in the corner of a room. For stand alone, pure horn this coefficient is 1, with this the horn is the bigger possible. curious thing is that if you calculate an horn with 1200 hz or higher is really tiny!

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C-Bag (Jan 6, 2016),

kbalch (Jan 6, 2016),

PJs (Jan 6, 2016)

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## PJs

> So does this mean there's going to have to be a major redo in the outer edge of the horn?



Dunno C-Bag its a bit ambiguous.  :Confused:  My hit is it's saying that on these "exponential" cones, if the length of the exponential curve (frequency tuning) is reached before the radius to the 90º curve starts the formulas don't work and you are on your own. So I think it's saying that the 90º must be included in the overall calculated length to work for mids and tweeters¿ 

From a physics standpoint my understanding is that sound waves are actually spherical in nature so in this case at these mid frequencies the when the spherical wave front passes through the cross section of the root of the 90º it starts to expand too rapidly and causes distortions in the wave front, generating noise of some kind...maybe a tinny sound or maybe an off scale harmonic¿¿ @¿@ -Dunno...a bit out of my league here.

Stefano:  :Clapping:  Great job on the profile, amazing you pulled it off so cleanly considering the issue with your vibrator! LOL As I indicated earlier I thought the index bit didn't have enough front rake on it so that may have contributed greatly to your finish. The other thing I prefer is to use hi-speed steel on aluminum and a fairly generous radius will give a much better finish. Aluminum can be a bit gummy and the radius makes the contact minimal so chips are easily discarded. A sharp tip angle will give problems if you have run out or slop in gibs or rigidity of the holders, compound or cross slide.

Would love to see a picture of your template if you have time and inclination. I was thinking that it would be much easier to machine a reverse cone as a template, then use that and Prussian Blue or Dykem to dial in your final cone to match. 




> formulas... i think the Excel sheet is good, there is a coefficient from 1 to 8 in calculations that is used for lowering dimension of horn in order to create "bass" horn positionable in the corner of a room. For stand alone, pure horn this coefficient is 1, with this the horn is the bigger possible. curious thing is that if you calculate an horn with 1200 hz or higher is really tiny!



Interesting about the coefficient, but like I said a mid or in particular a tweeter needs to be tiny at 1 wavelength so they must be exact multiples of a specific frequency at the starting point. For instance based on 340m/s speed of sound in air, 800hz would have a wavelength of 425mm but at 10khz it would be only 34mm and would have a LCD (least common denominator) of 1. This also doesn't compensate for the sound actually traveling through the Aluminum which result in respective wavelength of 7900mm & 632mm and creating some synthesis based on the coupling to the transducer... So I am still confused how it works for a range (800 - 10k)??? My hit is the exponential or hyperbolic curve is what allows that range, but there has to be some Guess and By-golly in it to tune it well?? Probably making this Way to complicated!!  :Sweating: 

Love what you made...can't wait for more!! Thanks, ~PJ

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C-Bag (Jan 6, 2016),

rendoman (Jan 6, 2016)

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## rendoman

> The other thing I prefer is to use hi-speed steel on aluminum and a fairly generous radius will give a much better finish. Aluminum can be a bit gummy and the radius makes the contact minimal so chips are easily discarded. A sharp tip angle will give problems if you have run out or slop in gibs or rigidity of the holders, compound or cross slide.



I think you've hit the issue! Tomorrow i'll take some pics of the inserts, maybe the angle is too narrow, combined with vibration and other things the finishing is not good. I tried a (brazed?) tool 20x20, but the result is similar... maybe something wrong in setup of lathe





> Would love to see a picture of your template if you have time and inclination. I was thinking that it would be much easier to machine a reverse cone as a template, then use that and Prussian Blue or Dykem to dial in your final cone to match.



you're so professional! you're right, maybe it's best way to achive perfection! the problem is that i'm a novice, with no much skills and tools for doing similar perfect object. As first step, I left some more alu inside in the processing (mostly in the inner part), not because necessary as for my possible mistake... that makes the job too long.
I'd like to show you the template, unfortunately my father threw away chips and other metal debris, for sure he Exchange the steel template for something to throw  :Evil:  But not a great problem, i drew some lines with angles on a used piece of paper, i can replicate the second horn. for now i havn't a template to show you  :Frown: 
I think at starting of polishing i'll try an internal mold with plaster or other material, in order to obtain a positive. Few words on contour, it's not completely a tractrix, i've modified the original drawing, half conical first part and half tractrix. I made this experiment some years ago and the results were excellent. 
I have no answer to your questions about "numbers" of horns, i'm not so studious unfortunately  :Smile:  still prefer trying and listening  :Lol:

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PJs (Jan 7, 2016)

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## rendoman

et voila! 
Past few days i had some problems, above all the breaking of cesso (wc)  :Lol: 

I take some pic of the inserts, i don't know what's the best use for them.
I tried to polish the horn with sand paper from 40 to 1200, but i found some problems. Sometimes maybe some dust from paper left ugly signs during passage, and the second, more important : i need to learn polishing :Smile: 
i tried with horn on lathe to put some white paste (i think the first of available in grit), difficult to apply because the shape, it sticks like glue to the inside of the horn, forcing me to remove with a wooden piece. the last pic is White + polish for car , not enough for me, it doesn't shine! it's something between satin and glossy ...
someone has some good advice? 
thanks!
saluti
stefano

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PJs (Jan 11, 2016)

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## PJs

Hi Stefano, Thanks for the update...sorry to hear about your plumbing problems... :Sweating: 

As for the inserts: These inserts have 0º rake (clearance angle) and in my opinion the .4mm (1/64") radius tip is way too small for a good finish. Here are some links to the Widia Pages for your inserts. Here is a chart for the Number description (Pages F8 & F9) to figure out what you have. D=Romboid, N= 0º clearance angle, M=Tolerance Class, G=Features (chip relief) etc. Yours are listed on page F13 at the top.

If these are all you have the only thing I might recommend is *if* you have a diamond stone you might *Try* to adjust the rake to 10-15º and give it about a ~1-1.5mm radius. This is approximate to what I use (final couple of passes) to get a pretty good finish to start polishing...but again I prefer Hi-Speed steel to carbide on aluminum.

Polishing: My experience is that you work a grit until you have a _very even_ finish all over, then move to the next grit up...to say 1200G which should be fine. If you are having a dust issues use a tiny amount of water on the Wet or Dry 1200 paper. I have some 3000-10k grit foam pads I use once in a while but typically don't need to. For aluminum and brass I always use Simichrome on a soft lint free cloth, as a final polish...best I have ever found...and tried a lot of fancy hi$$ stuff. Should be able to find it in good hardware stores or automotive store, even in Italy. Think it used to be made in Germany (Happich)?...its everywhere I think.

Hope this helps? Good Luck!

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rendoman (Jan 11, 2016)

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## rendoman

Thank you very much for the info PJs! I will focus on angles and good steel!
I think Tomorrow i'll try to find some simichrome or other italian available compound, i tried some minutes ago from start, adding ooo steel wool, some better result, but nothing of special :Sweating: 

1200 grit, old photo 


000 steel wool 


"polish" with cotton cloth, 3 hands

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PJs (Jan 13, 2016)

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## PJs

Looking Good Stefano. Hopefully you can find some Simichrome and can rework you inserts or some HSS ones for the other horn. Looking forward to your test results! Thanks, ~PJ

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## rendoman

I went to the dark side  :Lol:  6cm drill buffer, and a home made not good small buffer for the inner part... i hope monday i will find some better commercial new one. polishing with drill maybe it's the better way to do this job, now the horn is shining more than in photo. I hope i'll finish the first flange and do some test! See you on the next episode  :Big Grin:

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C-Bag (Feb 9, 2016),

Paul Jones (Mar 31, 2016),

PJs (Jan 17, 2016)

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## rendoman

Hi! it's long time since last update  :Big Grin:  ,I got a long flu and had to do other works unfortunately
I still have difficulties finding a tiny buffer for the small inside of the horn, dremel cloth insert are too short and I see that for polishing i need to press a lot. I will have the same problem for the next small horn of only 1cm throat ... i need to find something!  :Idea: 

apart polishing, i mounted driver-flange-horn for some test, sound is really good to my ears  :Big Grin:  very detailed and focused! i build a simple rod for microphone, i'm waiting the key of a beta test program (medianet audio pro solution), hope that program is easier than "speaker workshop" who needs specifics cables with test resistors and an Lcr bridge. 

OT: i'm planning a plasma tweeter
OT2: i found a box with Emergency button in scrap, i added last night a contactor, need a bulb light for voltage presence. I mounted on my lathe, it didn't have the Emergency stop

some pics as usual, the third photo is a generic layout of the new plasma speaker (horn will be 1\3), fifth pic it's a rat9 big mouse for size comparison

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C-Bag (Feb 9, 2016),

PJs (Feb 9, 2016)

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## C-Bag

Funny, i was just wondering about what happened to you yesterday Stefano! I guess that cold shop got to you  :Smile:  I'm glad you are over your flu and back at it.

Good pix as usual. As to a polisher, have you seen those special polishing balls for polishing aluminum wheels on cars. I think they have tapered ones. 

I have one of those Berhinger mic's and I believe because it's omni directional, it needs to be mounted vertically. I could be wrong. The whole sampling/testing/pinking the room is a very tricky thing I learned from my buddy who does pro sound for a living. From what he told me you have to be kinda close to get more of the speaker and less of the room. Im sure PJ's knows more about this than I do and will be along soon and enlighten us both.

Great score on the control box/ emergency stop! What a find.

What I'm wondering is how to make some kind of pantagraph/ duplicator for your lathe to duplicate the next horn. I would think it pretty critical to make them the same. Anyway good to see you back, carry on!

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PJs (Feb 9, 2016),

rendoman (Feb 9, 2016)

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## PJs

Hi Stefano and C-Bag! It is good to hear from you both and glad you are over the flu...there was a nasty one going around here too.

I like C-Bags idea for the buffer ball/cones. Generally they are mounted on twisted wire which you will need to be careful with. Probably wrap it with several layers of tape and maybe some foam too? I was also thinking of using a boring bar type that you could mount on the cross slide and compound to work it in with some pressure...although if you use your compounds wisely you shouldn't need a bunch of pressure.

I took a look at the medianet program and looks pretty good but they don't give a lot of details. When I did my sound table I used TrueRTA (24 octave version) for my spectrum analyzer and found it quite easy to use, accurate (as you can be with a sound card) and mainly it has a capture feature that ports the data to Excel which was what I wanted. Lots of good settings and options but it is important to create a configuration file with your equipment to give it a base line.

As far as the mic goes I pointed it downward into the flat table. Not sure if this was correct but the db level dropped off drastically when it was perpendicular to the table. The tricky part is placement distance IMHO. For my application I needed to take 3 different heights from the table face (1", 3" & 6") in a 4" grid pattern over the table surface. Speaker measurement is another story and believe the optimum measure distance is either 1" or 1' (C-Bags friend would know better I'm sure). Room measurement is a whole other ball game!! The other most important part is what you are driving it with and how. I drove the transducers with the HP 4ch signal generator through the Art4 amp while monitoring at the transducer on my O'scope for input levels. 

The direction curve for the mic is quite good and in reality it is well suited for room correction work but there is hardware/software and algorithms for analyzing the acoustics levels for optimum placement based on the responses to specific frequencies, pulsed, sweeps, pink/white, etc. My Marantz system has the feature built in and came with a mic. The interesting thing is it has multiple algorithms and storage options. Hard for me to get my head around it. Although I played around with building a voice analysis system to identify frequency/db ratios by octaves and to show harmonics as a subset...had to put it down finally but still think it's doable and may be worthwhile for determining stresses within the body/spirit/mind. Tuvan throat singers can actually create a binaural beats and IMHO is why it "feels" so relaxing or invigorating and adding that to an instrument or other singers in harmony or "disharmony" can invoke an amazing "well being" or health.

Ha!! C-Bag...I'm with you on the Pantograph. Ever since I saw Keith Fenner creating the boat rudders I have been on the hunt for how to do that!!

Looking forward to what you come up with Stefano...Plasma...Oh, My...shocking! :Lol:   :Hat Tip:

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C-Bag (Feb 9, 2016)

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## rendoman

Hi all! nice to see you  :Big Grin: 
The flu this year is really long, 2 weeks of weakness  :Flame: 

thanks for the good advice powerball, i think i'll search for something similar here, maybe I will be lucky and I will find a good store! 

I found some time ago this site from italian, he uses speaker workshop. I see many passages for calibrations with special cables and test resistors 1%. i see in freq response the same mic position is the same, radial the speaker... but don't know why, have to read better
Claudio Negro's home page, how to project and test a loudspeaker using Speaker Workshop

I think too, it will be so hard to duplicate... i will do a "mask" my purpose is to make the second similar, not a perfect clone, by hand is difficult to replicate exactly and maybe it's not completely necessary... 
how is a duplicator for lathe? i already heard of this but never seen one

today arrived all the basic parts, capacitors, resistors, sockets. i made coil in teflon - delrin

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C-Bag (Feb 9, 2016),

PJs (Feb 10, 2016)

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## C-Bag

I stand corrected on the mic, sorry guys. Mine came with my dbx DriveRack 260 and only one time did I ever have enough time to use it for the auto eq and thought it didn't work all that great. 

Sounds like not only was I too far away, it might have been pointing wrong....doh! I'll slink back to the peanut gallery again now......

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rendoman (Feb 10, 2016)

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## PJs

> Sounds like not only was I too far away, it might have been pointing wrong....doh! I'll slink back to the peanut gallery again now......



C-Bag - Front and center Please sir! Your thoughts are tied into this project as well and good ones at that! I have no idea that my methods are more correct than anybody elses other than a bit of research, however it did seem logical to me with the equipment I had and playing around before actual testing. The things I was looking for was a solid coupling of the transducer and any issues with harmonics/distortions from the table components.




> I found some time ago this site from italian, he uses speaker workshop. I see many passages for calibrations with special cables and test resistors 1%. i see in freq response the same mic position is the same, radial the speaker... but don't know why, have to read better Claudio Negro's home page, how to project and test a loudspeaker using Speaker Workshop



Stefano: I saw his website before but didn't delve into the minutia. From a cursory stand point it seems pretty complete except for doing it in an anechoic chamber and based on the equipment he had at hand ("Old Sound Cards"). It also looks to me he did a far & near field test (1-2m & .055D) which makes sense to me because of the dispersal curve of the cone/speaker.

As far as duplicating the second unit...all you can do is measure, measure, measure, and then maybe adjust the filter to compensate and balance the pair...if that is even necessary. 

I always want to know how it sounds in a working setting most of all. When I bought my Marantz I must have listened to 10 sets of different speaker system with music that I brought for testing. Finally choosing the Monitor Audio's that best fit my tastes and music/video...*& Budget!*

Interesting design and nice work on the Delrin cores. Thanks! ~PJ

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C-Bag (Feb 10, 2016),

rendoman (Feb 10, 2016)

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## C-Bag

> C-Bag - Front and center Please sir! Your thoughts are tied into this project as well and good ones at that! PJ



Aye aye Mr. Wizard sir! 

I'm always ready to learn, or unlearn. My lack of focus though tends to make me truly a master of none, knowing just enough to be dangerous. 

But I'm fascinated with Stefano's energy and verve! Makes me wonder if you ever sleepStefan! I do get a lot of ideas and energy for moving ahead with my audio dreams of building some new speakers for my own old stereo rig. My problem is just picking the best direction as I have from 1k to 22k covered with my EES Heil's.....it's all about trying to find the best cabinet/speakers for everything below. 

So the peanut gallery is paying attention!

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PJs (Feb 10, 2016),

rendoman (Feb 10, 2016)

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## rendoman

thank you! you're too kind! I'm Learning new things every day! 




> I always want to know how it sounds in a working setting most of all. When I bought my Marantz I must have listened to 10 sets of different speaker system with music that I brought for testing. Finally choosing the Monitor Audio's that best fit my tastes and music/video...*& Budget!*



If I understood well, your point is how to make them sound good, in whatever setup, right? I got your same impression with commercial type finished product. I listened to many different kind of speaker and mix of amp and source, in different rooms. I have to make a summary because is too long, imho room is important, but not so important as mix speaker + amp (i keep the source apart for now). A short consideration of commercial "mid cost, low-mid size speaker (including half new production of klipsch for exemple, excluding la scala and klipschorn Heritage) imho they sound bad as hell. I have always the sensation they sound strange in voice, mid and highs, anemic. Maybe that's the compromises for space, It is a coincidence but I never heard sound bad a "big and well made" commercial speaker, even in small room with square map. the first exemple I remember i listened a pair of tannoy Westminster in a ugly room. 
i think one thing, usually I play with separated parts, not a complete and finish product, then i have the possibility to choose the range and the loading of every components. It follows that if i can choose size, loading, number,type of driver and enclosure, I can setup them every time in a different way, and find the best sound to my ear. ( and to any room )

imho there are some few problem in most commercial speaker, i try to synthesize:

- new house have small room than old, than the need to use compact systems, and make them sound "good" in many rooms.
- good, fast, efficient and deep bass need high volume and at least a 15"
- factory can built speaker with 2-3 ways, but the problem is the range they use for every way. for me it's not good use a bass unit up to 500hz, when it overtakes this point the bass suffer and the mid even! I tryed xover of 10\12 and 15" at 1000-1500hz, no, they were bad over the entire range. It is the short blanket :Big Grin: 

after many attempts i choose to have the best for every range. true low bass, the woofer should be a true woofer, not a woofer used till Death  :Big Grin:  
the second things i like is to use a fullrange for voices and mid (also in normal reflex box, horn is my passion but a reflex can be good) just to avoid a crossover in critical fq range.

summing up to the maximum: single good parts with a good active xover and some wish to make listening tests make the speaker sound maybe different from a finished product with few possibility to setup :Big Grin: 




> But I'm fascinated with Stefano's energy and verve! Makes me wonder if you ever sleepStefan! I do get a lot of ideas and energy for moving ahead with my audio dreams of building some new speakers for my own old stereo rig. My problem is just picking the best direction as I have from 1k to 22k covered with my EES Heil's.....it's all about trying to find the best cabinet/speakers for everything below.



many thanks! if i may give you an advice, heil are so good!:
- one ( or better 2 ) 15" with good box, 20-30/ 150-200hz , 96 ore more db
- a couple of small and economic fullrange (even westra in open baffle), an or fostex, or an esoteric lowther pm4 units  :Lol:  (one of my dreams) from 200 to 8-10k
- heil ( yes i don't want to use from 1khz  :Big Grin:  )

with reflex good box, or open baffle or other similar loading they are easy to make, sound good and there isn't a great difference between sensivity of speaker. maybe the expensive parts are 15"woofers and coils (you can do) for 200hz filter...

.
..
...

after this lengthy discussion, i got some problem:
I tried some hours ago to drill some 6mm brass plate, ugly as hell! I don't know why but with good drill, near to exit the hole, the plate tried to lift wildly. I found an old broken and bad repaired flycut (it's flycut the name?), i tried to grind a broken threading tools, it cuts "good", but make bad sound.
I also have the impression that i should learn how to block parts on milling ... 
ok beat me, I deserve it  :Lol:  :Lol:  I make bad works sometimes 

a couple of new pic, i decided to put the 2 switch, one for filament and "low" 350v anode for modulator, and the second for the main B+ grouped to the left of ammeter. The big hole should be 45mm, in pic is 43mm.
I think next days i will complete the stands for the finished horn, then i will make some more test  :Big Grin:

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C-Bag (Feb 10, 2016),

PJs (Feb 10, 2016)

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## C-Bag

Always so much to cover on your projects Stefano. I guess we could argue that speakers are tools for listening to recorded music...you are certainly using a lot of tools! 

The Wiz makes an excellent point about so many factors in selection of equipment is mind boggling alone. But then when you add in real world application into your room it gets overwhelming. The added factor I now have is I can't have a setup that dominates the living room like I used to and don't listen at concert levels anymore. Much more modest. And my system is made for listening to acoustic music. 

I so appreciate your opinions and advice Stefano. And especially your opinions on other systems as that lets me compare to my experience with those same components. I totally agree with your accesment of Klipsh and I think of them when I think of horns. This only makes me wish I could hear your system even more. 

I also tend to avoid multi crossover/speakers as much as possible I think that's why I love Heil's, Magnaplanars, electro stats etc. I always wanted to hear a set of Ohm F's but never did. But all those speakers lacked authority in the bass. ESS sounded good for jazz but never seemed to have "thump" for rock. Passive radiators just sound kinda mushy for below 50hz IMHO. 2x15" or 2x18" in a folded horn cab is pretty good for PA but totally impractical for home  :Smile:  For me the 15" sounds to slow( the only way I know how to put it) for home. I'm stuck on 2x10" transmission line or baffle like the old Dynaco A50's. But I've not heard either in 30yrs, and unlike you Stefano, don't have the time and passion to throw into building either and find out things have changed. #1 being I don't listen to that kind of music anymore.

My idea now is to be able to build the low end, then bi amp through the dbx 260 DriveRack and do all the time alignment(VERY CRITICAL) and eq(it has separate notch, parametric,and graphic eq for each output) in conjunction with SMAARTLive to do all the realtime analysis. 

As far as I know a flycutter is more for milling flat surfaces, not for cutting holes like what you are doing. Your hole saw is a good way to do brass/copper. I would grind the cutter itself to cut narrower and have a pretty flat rake to it. That's why drill bits don't work to well because they have too aggressive a rake to the cut. It's fine until like you said, the very end it takes too big of a bite and try's to destroy itself.

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PJs (Feb 11, 2016),

rendoman (Feb 11, 2016)

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## PJs

*Well Said* C-Bag!!  :Hat Tip:  I too think it is a bit hard to stay on topic (building a pair of cone drivers) but it is the physics and Stefano's "Verve" that light the candle for me and spins this off in all directions imho. I woke this morning thinking that I don't really have the skill set to even attempt a speaker enclosure  :Head Scratch:  like you want. Frankly I'm having a difficult time as it is just building a hand crank/solar powered music box that is acoustically "reasonable" and bullet proof for my G-Son.  :Head Scratch:  :EEK!:  And Honestly I'm quite enamored/jealous with you having a pair of ESS's.  :Embarrassed:  I had an old pair of Series 5's for a while but had to let them go for space and needed a small lift to move them.

I'm with both of you on the Klipsh, tinny to my ears and no heart. Never got to hear the Ohm F's either but they were a wonder and still pretty much top of the line at ~$8k for the new ones, but hey...they have a Beta program!! ~¿@

I've always had a broad taste in music, from classic, Blues, Jazz R&B, Bluegrass, & R&R but over the Ages moved enjoy videos/movies tremendously. It's a heck of a load to put on a system, IMHO and all about the best for me within my budget & space. I go on small binges of listening to things like Les McCann and Eddie Harris to Liz Story solo (melt me) to a DVD set of Eric Claypton's Cross Roads Festival with a Goose bump & jump version of Joe Walshes "Mountain Way" in 5.1 (one of the best ever Music DVD/Festivals, IMHO). Then there is always Jimmy's Voodoo Chile on Vinyl...Oh My! Then back to Beethoven 7th...but Movies are probably the mainstay anymore...And would somebody *Please* teach the Foley/engineering guys how to balance tracks for Gosh Sakes.

I ended up with the Bronze Br6 towers & set (Center and Rears) for my system partly for price but mainly because it handled Liz Story's Steinway better than anything else. However I added a pair of Bose 301's I had, high up & tied to the fronts (Front B), mainly because of my room shape and size and they brought a little brightness. I'm not a big Thumper guy and only have a little Sony 10" sub which will literally rattle the windows in this old place and fine for my tastes. I agree that balancing the room and system is second only to matching the system components and Cables/connectors too. Probably spent 3 days learning & messing with mine to get it all right for my tastes...after break in. Which is one of the thing I appreciated too about the Monitor Audio's was the booklets gave a methodology for break in...absolutely necessary IMHO.

I took a look at the SMAARTLive and it's quite a package but pricey, and the dbx 260 is quite impressive. Think it will Do!!  :Drooling: 

Stefano: curious why you would us 6mm (1/4") brass plate for a panel mount? Although "Pretty", AL rack panels are my favorite and easy to work, and you could have a small piece like that gold anodized pretty cheap I would think. I agree with C-Bag about using a fly cutter for boring a big hole. Probably the other reason you got chatter is because of the air gap under the middle...would recommend a sacrificial piece of AL or even wood if you don't have that. Probably a better way would be to drill a large hole and use a boring bar to take it out to size. Don't know if you have one though and get using what you have on hand.

Till Then Guys...Thanks for the candle lighting and fun topic(s)!! ~PJ

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rendoman (Feb 11, 2016)

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## rendoman

Thanks for advices! I never seen in music or electronic shop front rack panel, but i see on some sites that they are cheap! a bit professional look, but practical! I used brass because i found some good plates from scrap shop. here it's difficult to find metals, hard to find metal in the size you want, and pretty impossible to find them at good price  :Flame:  I really like sturdy frame, massive and good looking. For sure 99% of my projects are oversized! :Lol:  
It's work for next days, the frame will be composed of:

- steel 15x15mm thick 2mm for the real frame
- top plate frame (base for the 3 tube socket, for transformer, horn and primary coil) in 1,5mm brass, 2 parts wide 10cm each and 35 cm long
- 316 perforated steel as faraday cell for coil ( have to think how to bend and create a nice looking one )
- bottom and lateral, for cover and shield, steel or alu 8\10 

I think it's a bit difficult to imagine the frame, i got all in my mind, i will show you soon! ( i hope! )

to be honest, i only have two broken and repaired old tools, one is in the last pic (and it's the only one that make big holes), the second is a boring bar in fact, with a small square blade, i think it drill till 22\23mm, but the body of the tool require a large hole to fit... for sure my method is wrong, but i think i need to make some other tools.... but we here in the right place for making tools right?  :Roll Eyes (Sarcastic):  :Roll Eyes (Sarcastic):  :Roll Eyes (Sarcastic): 

I took a macro of the blade after work... maybe because my fault, i let the tool gets blocked 3 times, i missed the outer part of the blade... but it's still working!
For the next holes i'll follow your advice to grind better the tool, and to put some wood under the plate, you're right i leaved too much air... i didn't want to hurt the milling machine, basically i'm noob  :Big Grin: 
and in second pic... ready for polishing again!!
the last 2 pic are the new camera just arrived this afternoon, for sure some of the next pics will be better than my broken old one  :Big Grin:  I used a ticket from ebay, 70 euro on 100 of minimum buy, in few word 70% if i spent 100 or more! I received this ticket half jan as many other people, but ebay says that was a software error. I wrote to customer care of ebay and after a couple of week they give me the same (true this time) bonus! If someone of you received this bonus, i recommend you do the same with customer care  :Big Grin:

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C-Bag (Feb 12, 2016),

PJs (Feb 12, 2016)

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## C-Bag

Watching this thread evolve it's funny how you say it's hard to find the metal you want at the price you want, but you always come up with some good looking stuff. I would recommend an import clamp kit and probably a 4" knock off Kurta style vice both for the mill. They are basic tooling for the mill and make work easier and safer. 

Making an enclosure for a custom piece of electronics is a real challenge. I've only done one and that was enough. I bought a strip unit of 4 mic pre's out of an old Quad 8 mixing board. It supposedly came out of a board that was in a famous recording studio in LA. I had a really hard time finding a case and then fabricated a front panel for it. Came out looking very vintage  :Smile:  I put the power supply in its own box, out board for isolation and because it was too big for the case.

When I was working as a mechanic/ fabricator/welder in fruit packing here in the Central Valley of California, I was always up to my neck in metal. And I could take home scrap out of the recycle bin(within reason) for free. The last company I worked for had a HUGE what we called "the bone yard" that was full of out dated equipment. There was probably 10 huge rack cabinets complete with rack rails, mounts, and screws. But even though I was not that great of a wood worker, I ended up making my racks out of wood. Because I didn't want to have to isolate each unit from the rack because of ground loops. I've made several racks for my PA and recording equipment and all the rack units were wood rack rails. Never had any problems with ground loops, hums and buzzes.

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PJs (Feb 12, 2016),

rendoman (Feb 12, 2016)

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## PJs

That panel will look great when its all polished up. And boy do I get all the hand work to get it to size, shape and finish. I agree with C-Bag about investing in clamps and a vice, even though I don't own a mill yet but used them over the years. The other is to get an import adjustable boring head. A few on e-bay but new imports aren't that pricey with bits. My brothers Grizzly (2"-50mm) one does surprisingly well. Nice camera deal! Look forward to your new pics with it.

Look forward to seeing what you come up with for your chassis...particularly the Faraday cage out of 316. Not sure if its available in your area but copper screen will work also and much easier to form. Stainless here is sometimes more than copper price wise. I've built a few over the years, my best was a separate power supply for a RX/TX pair of old Navy TCS's. I finished restoring the receiver but the transmitter had a broken shaft on one of the tuning caps and never found another...both in storage now. Also built a large HV 1.5/3kv supply and had to use heavy gauge AL to support the Xformer and in a make shift break at that. Built a small O'scope back in the day with a 3fp7 and a 4U rack panel front. Not much else other than some of the industrial stuff I did for a living.

I hear ya C-Bag about having access to scrap bins and discontinued stuff within reason...now its the junky's/scrap guys and they are pricey anymore. Also hear you about the wood racks. My Proto for the sound table stuff was an angle faced wood contraption which now supports my lathe with a 4U drawer for all my lathe tools and cheapy wood machinist box in the bottom. When I built the clinical version I used a laminate one from Sweetwater (in the pics before) and you are right about the isolation! Luckily the 3Ghz rack computer housing had a fair amount of caging in it to start with.

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C-Bag (Feb 13, 2016),

rendoman (Feb 12, 2016)

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## rendoman

I'm seeing that both of you have built and experienced many things! that's nice!  :Smile: 
It seems very nice the wooden rack!
you're right about the tools, maybe i need a import kit ( or maybe some professional used one ), now i'm blocking parts with few drilled Irons and m10 bolts, paying particular attention.
A question, this evening i used the second tool i have for boring, it's an old home made boring from 18 to 35mm, a bit crooked  :Roll Eyes (Sarcastic):  the problem is that for using this i had to drill 18mm with a mill ... i'm asking, how many tools I need for making holes from 20 to 50mm? I see some "large" modern boring head, but I think i need more than one right? I found some project of this, maybe i will try building one for test ... ( yes for now i finished money for tools ) 
I didn't think to copper for faraday... mmm ... for sure it's easier to ply. I have to think a good shape for the little cage don't know if round or square ... 
large HV 1.5/3kv supply is really though! i think that all parts and layout are well designed to run at this voltage!
I got some good pics of this friday night, weather isn't so good, and no one gets out... then i decided to go to my garage  :Evil: 
I found some scrap of Polizene, the green panel, and plexy as top cover. It's a bit large, but i prefer keeping safe capacitors and all high voltage parts, plus the solid frame of power supply allows to anchor with m8 to the iron main frame.
I post a pic of semi-finished front panel, that's why i wanted brass  :Roll Eyes (Sarcastic):  :Roll Eyes (Sarcastic):  i reject the poor "on/off" little plate of switch, too low quality. Maybe I will learn how to engrave some little plate with "HV", "Filaments" and some round decorations like those of rifles. ( yeah i love rifles )

The new camera is pretty good! It's a bit different from old coolpix, here I can't see "macro" key, but i can do this mode approaching really close to object with few zoom. Impressive the 35x zoom and the high iso, compared to my old camera this is a shuttle  :Big Grin: 

Ps: I post a couple of diy ...tool... an italian werewolf ragu' with double salamella of friday night (don't know the name in eng, Google translator can't help, it's similar to a sausage but more flavorful, 100% pig)

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C-Bag (Feb 13, 2016),

PJs (Feb 13, 2016)

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## C-Bag

Too bad there isn't a emoticon for "ohhhhh looking good". Especially the dinner. I can't digest pasta and wine gives me an instant headache( I'm not joking) so Italian food I generally stay away from. But the meal in the pix looked like my kind of meal. 

My brother is the expert machinist, so between him and you tube I've learned most of what I know. So anything I say might be suspect. I traded to him for a R8 boring head for my drill/mill. Besides the range of the head, being true and fitting the head of your mill properly would be most important factors I would think. The range of the head is also determined by the size of the boring bars you buy for it. The boring bar sets have different lengths and different size cutter heads. The smaller the cutter head, the smaller the hole it will fit into.

Another important tool the mill are 123 blocks and or jig blocks. Along with the clamp kit and milling vice they are essential for hold stuff steady and true. Wood crushes and comes loose. Nothing is worse than getting to end of a cut and having the piece start coming loose and mess up the whole thing.

Most of my machining stuff is made in China. My lathe and drill/mill and most of the tooling. My measuring tools from when I was an automotive mechanic is all Starrett and Brown and Sharp. You might get lucky and find a clamp kit but here they are only like $40 at Harbor Freight and you almost never see them used even though every mill you see on Craigslist has a kit with it. But you seem really lucky at finding stuff. Good luck.

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PJs (Feb 13, 2016),

rendoman (Feb 13, 2016)

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## PJs

Looks pretty good Stefano. A couple of things about the green base material and components. The Caps will tend to swell a bit during use and over time and depending on the type there is a small relief valve usually on the bottom where the terminals are. A lot of times if they rupture they will "Pop" the top loose, so I probably wouldn't press fit them into the holes but leave a slight clearance...the wiring will hold them in place or maybe a dab of hot glue if it will stick to the green stuff (HDPE-polyethylene HD??)...not much sticks to it? Second I might put a "U" shaped piece of AL sheet between the bridges and green stuff to act as a heat sink, maybe with some heat sink film applied, like CPU's to heat sink. If it is Polyethylene the heat may also loosen the threads on the hold down screws if threaded directly into the HDPE. Not sure what kind of power you will be making here??

Look forward to what you come up with on the Faraday cage. It will be interesting I think with the wires needing to enter & exit what ever shape you come up with, which may be something to consider for its effectiveness.

If the Home made boring bar is in Pic 4 you will need "several bits" for it to reach your size. Grizzly makes a 2" (50mm) adjustable kit for ~$90US. Not sure what your spindle is but should be able to buy/find just a head and put your mills size adapter on it...although it's better to get what you need as a kit. It will save you a lot of effort and time. C-Bag is absolutely correct about the wood giving way under pressure and heat transfer. It's definitely Not Ideal but can be used in a pinch if clamped properly with light feed pressure.

Nice pics and lovely looking home meal...love the sausage!

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C-Bag (Feb 17, 2016),

rendoman (Feb 13, 2016)

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## rendoman

That a nice kit! I have to do some research in next future, i see similar "nice looking" china product, the same sold on ebay europe. I need some good tools for making large hole , and even some good drill bits 
you have eye on electronic components! that's really good! ( because if I make some mistake you can stop me in time  :Big Grin:  ) 
you're right with caps, mine havn't valve, only soft top disk. I drill 10mm passing hole, then 20mm flat mill and as last passage my old boring bar, the result inside is ugly finishing, but i made a bottom pocket of 20mm with central hole good as exit in case of rupture. 
right! green panel is high density polyethylene, I don't know if some adesive can attach,i know that this material is used with chains transmission. good warning that the thread can melt with temp, i read that continuos temperature should be around 80°C and 120\130 melting point. I don't know the temperature of bridges in normal operation.
I buyed a bridge for B+ 1000v 15a alu type, and 2 1000v 1A and 400v 8A, B+ for now is 440*1.414= 622v from 50 to 90ma in normal use, maybe at red plate of oscillator can be go up to 150ma, and 380v anode voltage for modulator should be under 50ma , I think I'm in "safe zone", but precautions are never not enough :Smile: 
It's a good idea placing the bridge on alu, for heat and for a better Anchorage, i will think how to modify them keeping low height, maybe a little drop with milling.

Next thing to do is the real frame, small but capacius for all components  :Big Grin: 
see yaou next!  :Big Grin:

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## PJs

Over all I typically double my usage amps/ma to calc the wattage....looks like you may be around 100W worst case running. Double that and take a look at the specs for the bridges. Likely what will happen with the HDPE is it will soften over time as the chains break down so the threads won't hold as well unless you use a screw with a recessed nut on the underside. A simple small piece of 14-16ga aluminum sheet folded up around 2 sides and up maybe 3/4" (19-20mm) with some saw cuts in it will suffice. However many are available already made for just a few bucks based on wattage and form from electronic stores/online. Better to be safe than sorry.

There are adhesives that will work with HDPE (expensive 3M/Loctite)...not sure its worth it based on your design above with the through hole. Correct on the operating temp 80ºC although 110ºC is the rated continuous operating temp....best not to push it in my book, not knowing exactly what you have material wise. Personally I over build/engineer everything...to a fault sometimes.  :Lol:  

Look forward to what you come up for the case/frame. ~PJ

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C-Bag (Feb 17, 2016)

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## rendoman

Hi!
few pic of update, it's a mess! i don't know how to do with frame, maybe i should drill many hole on frame for future needs, maybe not. The bad thing is that as prototype i will use 3 transformer, but i don't know the layout of the final transformer. Problems are not related to frame but to brass panel. If I mount tube socket and I weld components, the finishing should be final, I will not able to polishing at ending... 
It's hard to make a proto  :Roll Eyes (Sarcastic):  (and we are at beginning)

I suspended powersupply with 4 m6, not a good work, i made the mistake of not disassembly parts, and drill bits pulled the green polietilene up, my mistake! i had to thread m12 and make a delrin grain, really a bad work, but for now is sufficient, i don't want for now to rebuilt the green panel

I had to change original size because the space inside was really little. The new size will change something in aesthetics, maybe some wooden polished with true oil, I don't know  :Head Scratch:  
a big BIG mistake is that I've used 15x15 1,5mm iron tube, with my old transformer welder (it don't go under 40A). Tube is too thin, holes everywhere with no current, i tried 1,6- 2- 2.5 mm electrode but in coupling position is too easy to make craters. And all because the shop in my area are so bad that keep only few size and they didn't have the 2mm thick tube. :Flame: 
The result is not so professional, nor so excellent, but fortunately it's solid! 

very bad episode at ending of evening, I was cooking the ragu' for Tomorrow... i opened the tomatoes tin with too many brute force that the tin ran away from hand  :Roll Eyes (Sarcastic):  ... I splashed half kitchen!!! 2,5 on the wall rest of tomatoes... a disaster!
a good news is that i put a led light for 230v on lathe

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C-Bag (Feb 17, 2016),

PJs (Feb 17, 2016)

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## C-Bag

Wow! When you say heavy duty you mean it! If there was a nuclear strike in Italy that box would survive!  :Smile: 

Before mig welders got so cheap here there was a device called the "metal stitcher" that you replaced the work lead of your arc welder with. I never used one, but the idea was it automatically moved the rod in and out making it so you could weld thin sheet metal. They used to carry it as Eastwood but it looks like it went away. My little Lincoln 175T mig welds thin stuff really well. But if it gets really thin I oxy-acetylene weld it. 

I think I would have gone the sheet metal route for that case. Even though I don't have a metal brake. I do have a small plasma cutter and I've come up with a trick for making boxes with it. I draw it all out on the sheet and instead of cutting the whole crease I leave breaks in the cuts 1" long and space them along the crease lines. Then I can bend the box by hand. There are of course the gaps where the plasma cuts are, but if it's a place where I'm worried about aesthetics I put aluminum angle over the cuts. Makes for a classy looking box. With places like Harbor Freight and Eastwood selling these inexpensive mig's and plasma cutters now for around $400 and they are getting great reviews they are more affordable than ever.

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PJs (Feb 17, 2016),

rendoman (Feb 17, 2016)

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## PJs

I agree that is a beefy build and could definitely survive a drop from a plane. Most of the chassis' I've built have been from aluminum sheet. You can create a makeshift break from angle iron or even hardwood. As Peabody and the way-back machine remembers the 18x24 chassis I built for the HV power supply, I did with a wooden makeshift break from pallet oak. Took some time and finesse to work the 1/8" AL to 90º but got there, and easy to adjust size for the final bend.

Your miters and fit up looked great Stefano, but welding is another story for me with out any mig/tig/arc. Have been eyeing a small mig but need to save and justify it for the stuff I do. I probably would have brazed it. Plenty strong enough and easy cleanup for this project. 

Nice Tip C-Bag on the Metal Stitcher! I have heard of those but thought they were large machines for HVAC or other sheetmetal work. Did find an article on it...very cool! Personally I love angle Aluminum, its really versatile, pretty straight and reasonably strong, and use it a lot.

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C-Bag (Feb 17, 2016),

rendoman (Feb 17, 2016)

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## Lee Fox

Ciao Stefano ! See this eBay listing for lots of information and a video.

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## Lee Fox

eBay item number:
160950348638

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rendoman (Feb 17, 2016)

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## Lee Fox

Ciao Stefano ! See this eBay listing for lots of information and a video.

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rendoman (Feb 17, 2016)

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## C-Bag

I hope I'm not hyjacking or belaboring the point, but I was trying to think of a pic of my trick for the plasma cutter and the only piece I have in the garage is the cover I made for the front of my mill/drill. I put a digital readout on the z axis and needed to replace the old plastic cover so I plasma cut this. I hope it will demonstrate what I was trying to describe. I first came up with this when I was having to make chain guards for belt drives in the packing houses I worked in. None of them had breaks either so this is how I got around it. It is that black cover and look close at the edge of the cover where the cut is, and the 1" "breaks" in the cut.

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PJs (Feb 17, 2016),

rendoman (Feb 17, 2016)

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## rendoman

thanks for advice! it seems a very useful tool for lathe! i see something similar on this forum, right? I was thinking to build something easier, maybe only a bearing pusher to use with tailstock.
You're right! the frame is really powerful  :Big Grin:  maybe too much for the normal use, but I like strong!
Interesting welding pistol! I never see one, i read about a solenoid that runs like a sewing machine, if i have understood it controls the current and at the same time provide a little movement for not drilling plates right?

i would like buying in future a good tig for aluminum, I was reading about "german" (for sure chinese with Toshiba mosfet) 

http://www.stahlwerk-schweissgeraete...-plasma-s.html

good power, puls, high freq, ac\dc, the problem is know if the welder is good for alu or not, spec are really good, but in practice? it will weld good? 

Update of today, i make some more drill, and the tiny horn for plasma! 58mm, ergal i suppose, it do flakes not chip, a bit more bright than the last aluminum. I try my best to polish, but with 10mm of throat is really hard to enter... same old problem  :Big Grin:  
I pressed a cloth with force this time, polished enough i think!

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C-Bag (Feb 17, 2016),

PJs (Feb 17, 2016)

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## rendoman

very nice done on milling! thanks for the pics, my eng isn't so good and of the last post i understood not every points. with this pics it's clear now that you cut this lines and leave short full metal parts for bending better!
... i think one of the next thing to think is how to model the faraday gage... got no idea for now  :Big Grin:

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C-Bag (Feb 17, 2016),

PJs (Feb 17, 2016)

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## C-Bag

Yes, sorry Stefano, I realized even English speakers probably didn't have any idea what I was talking about. Pix are better.  :Smile:

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rendoman (Feb 17, 2016)

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## rendoman

Hi boys!
pyrex is terrible!
I hate this glass! If anyone knows how to model and to cut is welcome!
the "big" tube is a 12mm dia, 1mm thick, inside a small ugly 4mm with 0.8mm. For my actual knowledge it's impossibile to cut, when hot it melts,but not liquefy. I tried rich acetylene, normal and full oxidising flame, but no great results. I tried also to keep a 6mm rod as "filler metal" , it sticks, but the chambers broke in 2  :Flame: 

At ending I made a "chamber", ugly as hell, a bad work! i tried keep on lathe the 2 parts to weld, when i free the tailstock for rotating the chuck and levelling the filler, the glass melted and keep off axis the tungsten rod ... 
Grinding machine makes flakes of glass and do disaster. sand paper give some better results , but nothing of good at all...

I have to think a better way to make a nice and replicable part. I have also doubts about the effectiveness of the thin glass chamber, can be good for ozone, but imho as horn chamber is completely unuseful...
I'm thinking if it possible to liquefy the glass into a mold, with aluminum or brass, or even iron can be easy to do a good shape... the problem is how to melt... this bastard pyrex glass melt at high temperature...

the good thing of today: I cooked "cassoeula" an historical recipe of north of italy with savoy cabbage and pork! I need some good single malt for digest

----------

C-Bag (Feb 18, 2016),

PJs (Feb 19, 2016)

----------


## C-Bag

I have to say Stefano, you should have your own reality show! I never know what you are going to do next! First in the shop doing machining then some adventures in the kitchen! 

Do you don't have any glass blowers close to you? There are some around here but glass of any kind is not something I've worked with. And I would think Pyrex is not something that's easy to work with. You and PJs lost me when you ventured off into heavy electronics and plasma tweeters. I can't wait to see the further adventures though!

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PJs (Feb 19, 2016),

rendoman (Feb 19, 2016)

----------


## rendoman

many thanks!  :Big Grin: 
this project really needs a wide range of different skills, for sure more then I have now!
I havn't glass blower or furnace-forge, i had a small only propane tank with short blower for tar and tin, but without oxigen I think it's not possible to reach temperature of 1500°C, working temp should be 820°C. 
I'm thinking to make an internal template on lathe, maybe in aluminum or brass (or iron) and then drip melted glass over the 2 joined tube to give greater thickness ...

the good new is that after the polishing of the tube smal panel, i can try to weld circuit!

----------

PJs (Feb 19, 2016)

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## PJs

I agree you need lots of different skills for these projects and maybe a reality show is in order!  :Lol:  Another approach you might try with the pyrex is to use the setup you did but instead of trying to liquefy the glass, get it to yellow and crimp it to the tungsten electrode with maybe a modified pair of old pliers? You'll need a crimp diameter about a 1/2mm larger than the rod. It should seal to the tungsten and might not create a "leakage" issue??

As I remember cutting pyrex tube is done by scoring the glass with a diamond then tapping it to break it off. Looking forward to the next episode! Thanks, ~PJ

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rendoman (Feb 19, 2016)

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## rendoman

Hi
small update
as usually i havn't found dremel diamond cutting disk, i will try with a diamond mill for dentist, maybe blocked on lathe. 
I made a sort of pattern from steel on lathe, work is not so nice to see, but size is good, I really don't know if this template will be good for modelling the chamber or not, but for sure i'll try! I think I will try your advice of modified plyers, and then melt glass on glass to reach some thickness

The others parts are new clamps for tungsten and the small one is the central point of earth (GND, don't know if it's the right name) in brass, drilled and threaded , i need some inox grains. hope tomorrow with polished tube plate i will start welding circuit and power supply... i'm curious to see the flame :Big Grin:

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C-Bag (Feb 21, 2016),

PJs (Feb 21, 2016)

----------


## C-Bag

Looking good

 :Popcorn:

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rendoman (Feb 21, 2016)

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## PJs

On the way to it! Looks like a pretty beefy Ground!! Me Too.... :Popcorn:

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## rendoman

Main parts done, not a perfect job, too many bad things linked to the thin 1,5mm frame, too thin for my welder. the tip for Gnd is solid and make good connection, i changed the front black screw m3 with inox type, same for tube sockets.
I left the left panel unpolished because I have to drill holes for horn, coils, faraday and other minor parts. 
I'm thinking about some fairlead or guides for cables, for sure main 230ac have to run from behind to front panel switch, , 6 cables for low voltage 6,3 and 12,6v filaments, and 2 different B+. 
I decided to put an xlr connector to the right side, near the lateral potentiometer, close to the pcl82 triode grid. Hope I'll not need for shielded cables!

and now I think I can start welding circuit and making big boooooom! :Roll Eyes (Sarcastic):

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C-Bag (Feb 22, 2016)

----------


## C-Bag

man, look great from here! I can't wait to hear from you how it sounds....

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rendoman (Feb 22, 2016)

----------


## PJs

Oh My! That looks Great!!  :Clapping:  I'd probably shield the hi-voltage lines for sure, especially on an all metal chassis. Looking forward to the Boooom! ~PJ

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rendoman (Feb 22, 2016)

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## rendoman

hi! 
small update again! I was a little busy, i only made a frame part helpful for keeping coil and last capacitor in position. I started to weld circuit, maybe a pcb can be more practical, i chose point to point. Hope Tomorrow I finish! Lot of time spent putting insulator and welding wire around, I have to think a better layout for the next plasma!
In this days I'm better in kitchen! I made the queen of cakes: crostata peer and chocolate! imho the best cake ever made

hope the next update i will show you some spark! :Roll Eyes (Sarcastic): 
In the plasma pics, the ensemble horn-chamber-primary coil and clamps is only for scene, I will drill the panel when i will sure that everything will be ok

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C-Bag (Feb 29, 2016),

Paul Jones (Mar 31, 2016),

PJs (Mar 1, 2016)

----------


## C-Bag

Looking good Stefano! 

Wow, the queen of cakes!? Looks like chocolate pizza  :Smile:  mmmmm mmmmm.

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PJs (Mar 1, 2016),

rendoman (Mar 1, 2016)

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## PJs

> Looks like chocolate pizza mmmmm mmmmm.



 :ROFL:  C-Bag!! Funny my SO and I were just talking about chocolate pie the other day...my mom made the Best...Sorry Stefano, but it does look good and creamy.  :Stick Out Tongue: 

Getting there Stefano and looks good! Would be interested to see a better picture of the HV coupling to your plasma tube if you get a chance.

Thanks! ~PJ

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rendoman (Mar 1, 2016)

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## rendoman

Hi! just finished welding 95% of circuit, have to think some kind of berths and facilitations like B+ points and other things. Space is really low, noval sockets are tiny and some resistor are big, the mix is not ideal  :Big Grin: 
It's not so good to see, many cables around, that with more space or better layout can be placed better. 3 different B+ and 3 different low voltage filament. plus audio in and 2 wire for tesla coil and ring. The welding are good and bright with old tin with lead philips. 
Tomorrow I'll take some pics, sorry I got some problems to understand the part "HV coupling to your plasma tube". On pin 6 of gu50 (anode) i have a capacitor that cut dc from coil. It's that part?

PS: thanks for the request, i see now a mistake right in this part!

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## PJs

In the last picture above there is a brass piece extending out of the green stand offs toward the cone...I was guessing it was your HV (hi-voltage) connection to the plasma tube at the mouth of the cone??

I get the wiring issues and difficulty in isolating the B+ from the audio especially. I'm sure you will figure it out fine!! Thanks for the update. ~PJ

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## rendoman

As soon as I come home I take the pics! this brass part couples the wire of the tesla coil with the tungsten point tip. for sure i have to shorten a little, 2cm of thread is really too much, i have to shorten also the coil and the chamber, if i take these sizes i got few space for the single transformer. After reading in other sites that this plasma produces lot of heat that it can melt tin weld of the coil, I try mechanical coupling with m4 grains, prcatical solution even for change tip.

For the transformer i'm searching some good products, i need for sure 2 secondary up to 250v and 3 different for filaments. I call an italian small maker, 120 euro each for this transformer, almost homemade...
I found this polish company that makes imho good products, even some waterproof unit. normal grade toroid cost really few bucks, "audio grade" with some more shield and resin core a bit more, and the supreme applepie tranformer is tested, it has many features but, above all, it has a top plate in polished inox that save me lot of time and materials to make a cover! even with the most expensive i spent less money than buying in italy ...

250 VA - Shop Toroidy.pl

Toroidal transformers AUDIO GRADE - Shop Toroidy.pl

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PJs (Mar 2, 2016)

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## rendoman

Et voila! hope I took the right part! that's the brass mechanical link coil-tungsten. I will use two m4 grains inox (as soon as i find them), one for keep the tungsten and one for the cable inside. For sure i will shorten the coil of 3cm, and a little extra 2cm from chamber, for sure I need keeping the size as low as possible.

I finished welding this evening, but as usual, the schematic finished at late night should sleep and pass the night  :Big Grin:  . Tomorrow, with the necessary calm, i will check powersupply, pin socket and all parts... and then I'll try firing! Hope Tomorrow to show you some good pics about little spark :Roll Eyes (Sarcastic):

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C-Bag (Mar 3, 2016),

PJs (Mar 3, 2016)

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## C-Bag

> I finished welding this evening, but as usual, the schematic finished at late night should sleep and pass the night  . Tomorrow, with the necessary calm, i will check powersupply, pin socket and all parts... and then I'll try firing! Hope Tomorrow to show you some good pics about little spark



LOL! Good job! I wish I had as much control as you do. It's amazing what checking the next morning can show up. Bravo and I hope the initial test goes well. I can't even imagine what this is going to sound like. Good luck.

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PJs (Mar 3, 2016),

rendoman (Mar 3, 2016)

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## PJs

Thanks Stefano! Those pictures show what I was wondering about. It does seem a bit long but will do for testing your wiring and the effect. It felt a bit dangerous with the 3KV exposed like that but for testing and tuning it'll do, *just have to keep your hands out of there!!* No Frizzy hair Please!  :EEK!:  I was also curious how you would isolate the cone and adjust the tungsten electrode tube to the cone? 

Can't wait to hear how it went and sounds!! Thanks, ~PJ  :Popcorn:

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C-Bag (Mar 3, 2016),

Paul Jones (Mar 31, 2016)

----------


## rendoman

Sorry for the wait but I'm still having some trouble tuning the circuit  :Flame: 
This night for the first time the circuit shows a little progress. It's not easy, but it's an experimental circuit, I have to hold on and make changes! 
Very little flame started with point of screwdriver, pretty purple and silent for now. Flame is not stable, it fires only at max potentiometer position, at 90ma, sign that there is still many things to modify .
Circuit is far even from a basic setup, but at least it starts! It's little thing, but it's better than no start at all  :Roll Eyes (Sarcastic): 
It's early to say something about, only i have to do lot of work on it! This circuit is bastard  :Lol:

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C-Bag (Mar 7, 2016),

PJs (Mar 6, 2016)

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## rendoman

This plasma is possessed by the devil!  :Flame: 
Jokes apart, this little bastard is tough. I made some changes this night, I think i'm on the right path now, but still far from result. For sure troubles with oscillator, coils collide with frame, and even with the metal edge of table! even if the circuit it's not running well, the strenght of field it's enough to ignite a 58w neon tube and keep light till 30cm from coil. I have don't want to short all link and cable now, for sure it's important with RF, but I also need to make changes easily without welding. I really don't know why, but even the frame is stealing energy from coils ... have to think some solution!

In few words: this circuit is really susceptible to many aspects of project,frame and enviroment ... but sometimes it's funny to play with it Emoticon grin
oh, it would be better to spend money with girls!  :Roll Eyes (Sarcastic):

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C-Bag (Mar 10, 2016),

PJs (Mar 11, 2016)

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## C-Bag

:Popcorn: 


You are truly a madman Stefano! Years ago I read a biography of Nicola Tesla and one scene described one of the many visits of Mark Twain to Tesla's lab. And he talked about that Tesla had just racks everywhere for florescent bulbs. No wiring, just the racks because when he fired up the lab all the bulbs glowed, just like in your photo. I'm sure you are being careful but being around that much high voltage would make me nervous.

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Paul Jones (Mar 31, 2016),

PJs (Mar 11, 2016),

rendoman (Mar 11, 2016)

----------


## PJs

Whooaah there big fella, I'm thinking a faraday cage is in order. Definitely have some RF floating around there and it will puncture the insulation to jump to ground _or you_.  :Headshake: 

Are you modulating the plasma with audio and at what frequencies. Hang in there, if you build it, sound will come.

A couple of gals for ya! ~¿@

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C-Bag (Mar 11, 2016),

rendoman (Mar 11, 2016)

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## rendoman

thanks!  :Big Grin: 
the good thing is that the power supply discharge in few second, and the tungsten tip is coupled with capacitor from B+ , that makes the work on circuit really nice!
You're right, enamel insulation burn easily when touched by spark. This high voltage is really hot compared to its small size! Even the plasma flame is so hot, i smell few ozone with this flame size, for sure pyrex chamber and faraday cage.
I have to take a small mp3 for making tests, my old cd is not running, my old tape also  :Lol:  , I don't want to attach as test my Scarlett soundcard , for sure nothing happens with capacitor placed on entry, but still prefer to sacrifice a cheap player

I didn't think that a small coil as mine can light a 58w neon, it surprised me a lot! thanks for advice, high voltage is Always a danger! 
Hope I will post some better update next time  :Big Grin:  I gain a couple of mm of flame each week  :Lol:  maybe in may the tweeter will be good !

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C-Bag (Mar 11, 2016),

PJs (Mar 11, 2016)

----------


## rendoman

Hi! new update! 
This plasma is similar to Sasha Grey, it sucks current like a princess!
The final part of circuit is not running well, got a nice flame but it drinks too much bourbon, tubes and coils run too hot imho, have to make test, for sure I want to avoid burning tubes.
Flame is hot, really hot! I can smell a little ozone only with nose up to flame, not so alarming. Flame is silent, completely no sound from spark! Got some noise from 2 transformer of power supply, not a big problem, the single unit will be a toroid, maybe from poland, covered with resin.
Still not have auto fire, i hope i will tune the circuit. I have to improve fuel consumption and interactions between coils. Maybe frequency is really too high... I'll do some test!
Really impressive interactions with objects near, without metal shield around flame coil the metal edge of the wooden table gives spark to my hand! Without shield if you touch the edge the flame lower size!
I never thought that the cage was the first part to be designed! I discover new things every day! Have to think the shape, and how to create a good and nice one! :Roll Eyes (Sarcastic):

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C-Bag (Mar 17, 2016),

PJs (Mar 19, 2016)

----------


## rendoman

Hi! I begin to understand why there are few plasma tweeter and they cost so much... developping the circuit is really hard!
I tried different coils, resistors, capacitors but the tune isn't easy and it's not trouble only working on circuit, it's a complex set. I built some new coils with lathe for test. It's really impressive that very little changes can make huge difference or destroy the tube. In the 3rd picture under 10 sec up to overdrive can turn the final tube bright red. I buyed some testing equipment for doing measurement, a frequency counter and a lcr meter, for sure they can help, hope they get here soon from China! I'm searching in this days for a good oscilloscope with probes. 

Have to make some steel gage all around frame and coils, fix in different positions coils for easy substitution. Unfortunately I'll have to modify many parts from original idea ( and I don't want to sacrifice early 316 inox )

In the meantime I carry on for easter with pear and chocolate cake and some good belgian White  :Big Grin:

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C-Bag (Mar 24, 2016),

PJs (Mar 27, 2016)

----------


## PJs

Thanks Stefano and Happy Easter! This isn't a simple matter to work out for sure. You don't see them much except for very high end applications because of the costs involved to develop it to a frequency range for the application with out harmonics. But there are a few like yourself still working to dial them in. I'm still unclear what that range is for you also. Full range 20-20k or what? After all of this I still don't know if you designed this circuit or found it somewhere(?), plus we started out with making very cool cones on the lathe.  :Wink:  

I found a couple of links for you. Most of the stuff out there now uses IC's not tubes.

This one seems closer to what you are trying to accomplish but uses a brass horn. 



 and straight out of the plasma...simple computer power supply and a couple of coils, caps and note his comments about the electrodes. Simple but very good sound but can't see if he is driving from an MP3 or what.

And here is a white paper from U of I. Note how he is modulating the flyback with a PWM chip (pg. 5+) and the differences between a full wave vs half wave rectifier circuits and their harmonics.

 :Popcorn:  ~PJ

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C-Bag (Mar 27, 2016),

rendoman (Mar 27, 2016)

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## C-Bag

WOW, that's crazy! Now I see what you are looking for. I appreciate that the guy messed with the plasma and made it very convincing the plasma was making the sound not some other speakers. It's hard to tell with the camera mic's and my crappy little speaker on my iPad exactly what it sounds like, but it's amazing a flame is reproducing music.

 :Popcorn:  Indeed!

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PJs (Mar 27, 2016)

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## PJs

It's about sound pressure waves created by the modulated plasma. A shortened story from the Peabody and way-back machine...back in high school a buddy and I talked across light using one of the first photo diodes a (Fairchild Semi) and a lab spectrum tube for a science/physics project. Basically we modulated the neon type transformer for the helium tube with an amp and microphone and connected an array of the diodes stuck in a single hole rubber stopper ( :Lol:  still cheap and cheerful to this day  :Smile: ) to an old wire recorder to demodulate the signal from the diodes to a head phone. Seems like that was around 67' yet the principles are the same because the helium is basically in a plasma/ionized state but enclosed in the tube so we couldn't hear it from the tube. 

And now we have fiber optics across the country and world for that matter doing the same thing essentially but with some serious bandwidth and sophisticated encoding/decoding going on. We're gonna need some bigger bags of popcorn over the next few years I think!  :Popcorn:  ~PJ

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C-Bag (Mar 27, 2016),

rendoman (Mar 27, 2016)

----------


## C-Bag

"Peabody and the way back machine" LOL! I wonder how many that means anything to?

Once again I'm blown away with the tech you've been part of Wiz. Mighty deep bench around here when folks come out of the lurk.

Referring back to your linked vid, did it seem the plasma was directional? It seemed he was demo'ing that when he was standing up and moving around. If so, why would you need a wave guide, other than maybe focusing the sound and maybe keeping things away from the plasma? It was also real hard to judge how loud it really got. It would seem it draws a lot less amps than Stefano's rig, no?

So many questions and so little knowledge on my part. But it is extremely interesting! Gotta pop another bag  :Popcorn:

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## rendoman

Hi all and happy Easter!
If I can express my humble opinion, on the net there are many circuit with "strange" solutions and components, in few words, many circuit not running or performance not so good.

Thanks for the links! I wrote to conscious flash, he gave me some advice, but he said that his plasma with gu50 resonate at very low freq (1mhz +/-), it's clear because he used a very tall Hv coil. He said also it was a "stand alone project" not for hifi use. I want to replicate his low freq coil just for experiment, to see if the circuit runs (with autofire).

I think that big flame with flyback tranformer is good only for show, not for audio. For sure "tesla people" make this because it's funny and cheap, but it's not good.. I tried flyback years ago, they are not made for keeping current at high freq, and with low freq we can't talk about hi end use. I destroyed 3 or 4 flyback, and audio was really poor with noisy flame.

I did some research on solid state, mosfet type plasma, but for high freq troubles everywhere and very poor efficiency.

The base site for diy plasma tweeter is this, of Ullrich Haumann 
Ulrich Haumann's DIY PLASMA TWEETER

It's a very good starting point, with info on all commercial type and diy schematic (hybrid and full tubes). I spoke with Ullrich and he said that the efficiency was really, really low, even with the "turbo" tube version. 
My schematic uses the same concepts as that of Haumann, there is the last tube that is a class C oscillator tuned with few parts and cathode to gnd, driven by a modulator with a series resistors with potentiometer that modifies the voltage in g2 of final tube. The first "little" part is a normal audio amplifier with triode+pentode.
I only wanted to use different tubes, pcl82 (triode/pentode specific for audio) and el84 as modulator, then cheap and strong Gu50, but the big basic parts of circuit are the same. Haumann was right, 27mhz is a right tube for oscillator, it helps keeping flame silent , efficient and good sounding.

I havn't the truth in my pocket, and I know that before speaking I should do a trial run, but Il you see the schematic i can tell you something:

- with 600v B+ and 350v on modulator , nothing happens
- with 600v on both modulator and oscillator something happens
- adjust g2 to 60-90v for use, at the moment i can't keep the voltage so low (or the current so low like Conscious flash ) the circuit starts at a minimum of 130v till 300, i'm completely over range.
- maybe the problem is something in frame-cables- optimisation, but with 100\200 uH coils, nothing happens, my coils are bigger non slightly... 



For sure my circuit is not tuned well, but i see too many strange things in different schematics, and either some friends that experienced plasma tw building said the same.

if you've come this far, you can feel that many builders stopped developing circuit as soon as first start, and don't replicate for stereo. For sure this oscillator circuit is 5 parts, but it's really hard to tune.

Cbag you're right, my circuit is drawing lot of current! it's good that the flame even at full power is completely silent, but the grid of gu50 is a bit red and that's not good. I post my facebook video of the flame, with no sound ( i'm focusing on oscillator parts for now ) you can see the ammeter is nearly closed to 190ma, but if you see the color and the shape of the corona discharge is completely different. Conscious flesh seems to have a longer flame, more narrow and not so stable (see angle) with less current.

i talked also with a owner of a commercial Corona, and he said that in audio use, flame is 5-6mm, really tiny compared with mine... but i want to improve performances of entire circuit

The choice of horn comes to the need to use quartz or pyrex cell to degradate ozone. For sure 360° sound can be a great experience, but for closed rooms it's better avoid ozone, and the cell can help a lot. Horn for sure helps keeping flame low, it's at least +10db without touching flame size, that can really help with high efficency system

https://www.facebook.com/stefano.ran...8729516698000/

I hope I have not bored you with this technical info  :Big Grin: 
what do you think at the light of the new information?

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C-Bag (Mar 28, 2016),

PJs (Mar 27, 2016)

----------


## rendoman

sorry i forgot a thing  :Roll Eyes (Sarcastic): 
My goal is reach 1000\1500hz to 20khz , If i can run the flame at lower frequency is better, I aim to keep "tweeter" range with no noise and wonderful sound

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C-Bag (Mar 27, 2016),

PJs (Mar 27, 2016)

----------


## PJs

Happy Easter C-Bag! Yes it is directional to a degree. I believe the sound comes out of the plasma radially and probably loudest at the peak of the flame for a 2 electrode system. As he moved to the left and away the level did decrease as I think the sound is least, in the plane of the electrodes. As for the wave guide I would say that is what helps focus and tune the frequency range. The higher the voltage (more pressure) the louder it can be with out one. If you look at some of this guys videos on a modulated Tesla coil you can tell by the length of the spark he is cranking out some serious voltage as well as sound pressure.

The one in the video above is using a 2 electrode system...much easier to start and not as high a voltage, although I would guess by the length he was pushing 25-30kv. 

The big trick is to be able to create a corona/spark from a single electrode centered toward a cone. If you look at the second link above about half way down the page you will see what I mean. 

He says; _"The closed glass discharge chamber confines the discharge increasing efficiency of the speaker and reduces the production of the ozone . The discharge chamber is connected to the brass horn which improves the reproduction of the lower frequencies."_ The picture below this statement shows the tube, electrode and an exciter coil around the glass to get it going and plugged into the horn.

I only saw one of these back when rocks were formed and there wasn't a cone on it and was 2 electrodes...not safe for normal humans is the other reason they never made it to the public realms and the RF will play havoc around the hood. I believe the frequency response is pretty phenomenal from what I remember as well as the quality. The Tesla versions are real popular in with the Techno crowds and a lot more Staccato.

S'all I know...more popcorn and ozone please. ~PJ

----------


## C-Bag

Thanks Stefano. You are on another plane of knowledge from me with electronics. I'm sure the Wiz will be along soon and understand all. Interesting that the Quartz/Pyrex and horn are part of a means to keep ozone down. Like to boost the efficiency? Or as a catalyst? 

I was hoping that you were not going for such a huge flame as it seems dangerous if nothing else that much heat in a horn would sure mess up your nice polish job in a hurry  :Smile:  a big tube amp already puts out a lot of heat, having two plasma torches going on would be hell during the summer! Also you are going for a single flame, not double like in the vid PJ's/ Wiz posted. 

Interesting my old Heil's operate at the exact same frequency you are wanting the plasma for. I salute you for your diligence. Thanks for the update and stay safe.

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PJs (Mar 27, 2016)

----------


## PJs

Thank you very much for the details Stefano. You've clearly done your research!! It makes much more sense to me now and do believe Ulrich's circuit is a good starting place. I also appreciate that you are going the many extra kilometers  :Wink:  to eliminate the noise (flame silent) and adjust the frequencies to your needs. A couple of things I don't get about his modulator circuit diagram/designations though. 

1. What does TP filter stand for? I get that it is a 1.5MHz filter after the HP filter...basically he has created a band pass between the 2 filters but it seems an odd configuration, almost like a notch filter. Yet the curve shows a clear notch at about 2.6k?? I could be having a brain freeze but don't ever remember one called a TP filter.

2. Why the pull up to 100V feedback to G2 on the EF86. Is that to increase his gain to the ECL82...just seem pretty high? Your coil turns could be why you need more >130V to get it started.


As for the RF side of things a couple come to mind for yours. 

First is that Grounding is extremely important as well as shielding. With your transformers on a board and every thing else in the chassis bringing all grounds to "0" is important. A little leakage can be fed into the system and wreak havoc on you grid lines. His shielding also with the perf metal seemed adequate but might consider more of a copper mesh or screen type...more porosity and more wire. 

Second is he was very clear that he would build a 3 area system next time for isolation and heat. Again grounding and shielding must be considered strongly but maybe a bit easier to do.

And third the quality of the tube. In your case you have run your tubes to the edge and back several times and may have damaged the cathode/grid connections or warped the plate on yours. Also the filaments may be weakening under the load conditions they've been under. All of that can cause weird things to happen with frequency and capacitance.

The other thing I noticed on the video on FB is it looks like your have many more turns of smaller wire?? Also something about the feed back 1/2 turn and that resistance/capacitance values may need adjusting to temper the feedback to help with your flame control...especially if you are putting 600V into both plates...but may be indicative to damaged tubes?? Also that music/audio on FB was not coming out the plasma right?? 

It's a fun mystery and sure you will get it. Personally I might roll back to Ulrich's coil/feedback design and try that...if it is still weird check your tubes and grounds/shields. Thanks for the great ride!! ~PJ

----------

C-Bag (Apr 10, 2016),

rendoman (Mar 28, 2016)

----------


## rendoman

Hi! Thanks for advices!

Got no idea what the second filter at entry of first stage, the first high pass is good to avoid clip of audio in "low" freq, can the second be a Rf filter? I really don't know 

I never study ef86 circuit, my audio circuit is a datasheet manual pcl82 amp, with pentode configuration at 272v anode, classic from Philips.
https://frank.pocnet.net/sheets/020/e/EF86.pdf 
From this pdf of ef86 rg2 390k, something less Haumann, but pretty close, we can assume that the output voltage is 62v from this stage . I don't know why use a pentode as first stage and a triode of pcl82 as second before pentode modulator... I used triode + pentode for audio and then another pentode, this seems to me more logical, or maybe i'm wrong  :Smile:  

I'm trying different flame coil, all with 1mm copper wire, different lenght and diameter, from 20 to 40, 10-40 turns. the only one that run is that on video (calculated as haumann, 8,9uH, if i remember correctly, hope i get in 3 weeks the Lcr meter i buyed from china). 30mm dia like haumann don't run, plus the 100uH on anode is completely unuseful. I used tons of uH more, with a hand made coil on toroid iron powder that help to keep the main coil "safe" . It seems strange, but with 2 coils, the first one near to anode becomes hot really fast.

I need at least 130v to ignite flame in second stage, g2 of pl509 (haumann circuit), that's the voltage applied to g2 of final tube.
you're right with tube quality, I tried change all 3 tubes with high quality new one, but nothing happens. I see another curious thing, I start only filament for 30 sec to warm up, then fire B+, it tooks 2 minutes for reaching the maximum current consumption. Tipical maximum flame with cold tweeter is 150ma, after 2 minutes current raise at 190ma and flame gains body. With this running config I got no problems, soft start, but no same weird things as with Others coils.

Music is not applied to plasma for now, because I want to take one problem at a time :Big Grin:  
Feedback is not so effective in my test, half or full, position in middle of tungsten - coil - up tip gives few results, even the 10nF , I changed with 6,8 3 and 1 nF but I didn't see something different. 
Resistor G1 - loop changes polarisation of tube, this make differences.
g2 voltage in my setup is higher than Haumann, I can't fire till 130v, for sure it's a question of different tube, russian tube have poor datasheet , but i can maybe use data from LS50 german tube, the gu50 should be a copy of this 

http://www.mif.pg.gda.pl/homepages/f...043/l/LS50.pdf

Next days I will make something for frame  :Big Grin:

----------

C-Bag (Apr 10, 2016),

PJs (Mar 29, 2016)

----------


## PJs

Thanks Stefano. Food for thought from experience...When I get to a stuck point it is easy to get into a hurry up, try this try that mode and usually forget to document what I did and the Results. I relate it to trying to fight my way out of the inside of a balloon!  :Brick Wall:   :Gunfire:   :3 Stooges:  Usually I find that letting it go for a day or two, something bubbles to the surface that either puts me on the right track or the actual solution. Allow some Ω time. ~¿@

The 1.5Mhz filter is a bit odd to me too, but it's mainly the configuration of the 2 filters in series. I do not consider it (1.5Mhz) an RF filter in this circuit.

As for the coil builds...Start with the calcs and work a little either side of what is needed. The 10-40 turns is a big swing...especially changing diameters too. Document each!!

Had another thought about the coil and the proximal capacitance effects. Maybe you are experiencing issues because of that??

As they say...Rome wasn't built in a day...but it did get built...as well as the Sistine chapel. ~¿@ You'll get it built too! Thanks for sharing with us. ~PJ  :Popcorn:

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C-Bag (Apr 10, 2016),

rendoman (Mar 29, 2016)

----------


## rendoman

Hi!
Big update tonight
The new coil is running better than others! Full gas flame it's a little bigger now, but the main thing is that now lowest flame possibile (with closed potentiometer) is stable and is +/- 6mm after warmup. Tube oscillates better, less heat till 150ma, after grid become red, but it's good, in this conditions it's 70v over maximum rating. I need the measurement tools to drop a line, but I'm happy to see that I'm on the right side now, even if there's a lot of work to do! An other good thing is that power supply make less noise and coils runs colder.

Got a question for you, I noticed a change in flame color, till 1cm +/- it's a bright purple, when I push the limit flame becomes white, not only in the flake (idk the correct name, it's the outside of flame) but even the dart is clearer. Actually I don't know if it's matter of power, or maybe some frequency change. Next days I will try to vary the tuning freq, Hope measurement instruments will arrive soon! I need to know at which frequency the oscillator is running. 

making of the new coil
   

play with flame, the last picture is the minimum new flame at full closed potentiometer

  

  

Olive all'ascolana and strawberries kiwi cream pie
Ricetta Olive all' ascolana - Le Ricette di GialloZafferano.it
https://www.finedininglovers.com/sto...ives-ascolana/

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C-Bag (Apr 10, 2016),

PJs (Apr 8, 2016)

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## PJs

Looks like you are getting a pretty good corona now, small and tight! Nice Going!! Good your power supply and coils aren't straining (humming) now. Hopefully your new instruments will help answer some questions for you about frequency/power etc.

Not sure about your question but think you are questioning/witnessing the oxidation of the atmosphere with the larger white flame/corona from more power being applied (picture 6)? It may also be some oxidation of your needle as the picture has some yellowing out toward the edge. Forgot what material but seem to remember tungsten alloy for your tip??

Question for you. I can't tell from the pictures but have you moved the 3/4T coil up and down slightly? 

Thanks for the update, nice progress. ~PJ

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C-Bag (Apr 10, 2016),

rendoman (Apr 10, 2016)

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## rendoman

Hi!
you're right, the tungsten rod shows some oxidation, I can try grinding the tip in order to see if something change, maybe the flame can oxidize the tip continuously during operation? I remember old chemical exp with copper sulfate and flame, it can be something similar in fact 

I tried different position and different capacitor + resistor of the 3\4 reaction loop. separate discussion for components, because they change with main coil, i adjust the position of this loop with neon tube. There's a range of half inch about in which the strenght of the field is stronger, using neon tube it's pretty easy to locate the best position  :Smile: 

I see another good thing with the new tuning, semi faraday gage is still helpful, but the negative interaction with the environment is decreased, as temperature of coils and even temp of power transformer. For sure it drains less current relating flame size. Excepts for overdrive, datasheet of tube said maximum operation value of 250v, at this driving voltage i got 130ma at flame, with great size. 
I'm going to make some modifications on circuit, hope to got some news in few hours  :Big Grin:

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C-Bag (Apr 10, 2016),

PJs (Apr 11, 2016)

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## rendoman

Hi!
This evening I tried some experiments with audio, for sure strange things happened! Got huge troubles with some audio tube connection, maybe due to oxidation of pcl82 socket, then terrible Gnd hum and buzz from flame. I tried different things, the big problem was m6 inox allen plus nut close to reaction ring, it's a couple of week that I see strange behavior of that component. I remove the part and the flame starts oscillating good with no hum sound. Impressive? This circuit is really bastard inside! 
Few things about video, the cam is a china gopro, sound is not good, audio tape is really old and walkman has poor output (i tried with my Lm3886 amp of 15"sub , very low output). There is a lot of work to do, sound is pretty good! i'm not sure about xover filter at imput of plasma, i think I'll remove soon. Volume is not so bad with 110\120ma flame, more or less gasoline gives few changes in spl, I found the best position with this value. Got some bad rumor about audio first stage, pentode loading resistor 20w ceramic type runs pretty high temperature during operation, it's barely touchable with finger (I got trained welding fingers  :Big Grin:  ), imho this huge amount of heat can be avoid using a output transformer, maybe some more power can be achieved! It's early to speak about, but my impression is that amplifier is not enough, maybe it needs more then a small pcl82 pentode to run well, or more likely I have to optimize the final circuit and then think to audio part. The good news is that the coils are cold, but the B+ anode transformer after 3 hours of game is something about 60° , like a normal tube amp +/- 
Ps: the cable is audiophile grade! You don't beleve me? Maybe you're right! at least welds are good  :Big Grin:

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C-Bag (Apr 10, 2016),

PJs (Apr 11, 2016)

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## PJs

Congratulations Stefano, you have successfully modulated plasma with audio!! A big feat! Couple of observations/questions.

Did you feed your tape directly to the grid of the tube? What is the output level of the tape in volts?

There was a definite clipping at several points in the video. Not sure what you were doing at the time with the controls but a few of them felt/sounded like a low frequency ground pounding clip...Ground noise build up through a cap?

Do you have any way to feed a frequency generator sweep into it with a constant output voltage?

Baby steps now...to dial it in.

Terrific! ~PJ

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C-Bag (Apr 11, 2016),

rendoman (Apr 11, 2016)

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## rendoman

Many thanks!
I havn't measured the output voltage of walkman, but I want to use a soundcard of old pc to make some test, with this I can use even a frequency generator. At this time i don't want to use my Scarlett 2i2 soundcard, I prefer be safe  :Big Grin: 
The tape is applied to a high pass filter at imput (don't know if it's running good or not) then triode + pentode of Pcl82 tube. Flame now is better but there's lot of work to do, it's not stable with audio connected. Troubles with starting and restarting, it's a clear sign of bad tuning frequency of coils imho. In video I try different position of both volume control and flame:
- sound is nice, clear and loud at low-mid flame. optimum is from minimum 60 ma to max 100\110ma, when big flame appears volume lowered and quality decreases.
- if I raise the volume of audio too much, the flame turns off, i think the oscillator stop running, and it's difficult to restart

I think the trouble is the oscillator and the length of cables - position of components. Maybe 3w pentode audio stage is not enough to play louder, there's still this possibility  :Head Scratch: 
I'm focusing on main and block coils, I found that they are responsible for the major changes, I just finished a new double turns coil, as expected circuit runs better. Hope freq counter will arrive in few days, that's my only way to see at which freq circuit is running.

you're right! now baby step each time, it's like "labor limae"  :Big Grin: 
I'm thinking of close all side of plasma, put in orizontal position and regroup in small area all mammut for changing components, not an easy job, but maybe the best choice

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C-Bag (Apr 11, 2016),

PJs (Apr 11, 2016)

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## rendoman

sorry I forgot pictures

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C-Bag (Apr 11, 2016),

PJs (Apr 11, 2016)

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## rendoman

Hi
I want to make some changes in power supply, I'm thinking that can be more helpful tuning coils and circuit with final voltage, and not with the reduced one.
I tried a voltage doubler with 4x400v capacitor in series, an huge waste of capacitance, but my only way to use a doubler up to kv. Voltage without load is 1016 volt now, with load connected I think i'm in datasheet manual of tube. Hope it will give me some good results in flame stability and autofire.
keep fingers crossed for me! :Big Grin:

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C-Bag (Apr 19, 2016),

PJs (Apr 18, 2016)

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## PJs

Food for thought...website:

_"The Cockcroft-Walton multiplier serves as a more efficient high voltage source for photomultiplier tubes requiring up to 2000 V. [ABR] Moreover, the tube has numerous dynodes, terminals requiring connection to the lower voltage “even numbered” nodes. The series string of multiplier taps replaces a heat generating resistive voltage divider of previous designs.

An AC line operated Cockcroft-Walton multiplier provides high voltage to “ion generators” for neutralizing electrostatic charge and for air purifiers."_


Used them a few times back in the day a few times. Just keep in mind the ratings of the components and that each successive stage is less efficient.

Did you get your test equipment? Thanks for the update! ~PJ

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C-Bag (Apr 19, 2016),

Paul Jones (Apr 20, 2016),

rendoman (Apr 19, 2016)

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## rendoman

Thanks for the link! Very nice with graphs and info
Yeah I got only the Lc meter, frequency counter is still on the mule's back  :Lol:  It takes really a lot of time to shipping with normal post from china... i buyed also 2 of these:

Nebbia Sistema Lubrificazione Spray 8MM Tubo Aria Tornio Mill Esercitazione DB

A friend near my town buyed, I hate emulsion pump, it makes a lot of sludge. I use it occasionally, it's more time that I spend to clean pump than the time i use milling machine. I want to use a small fridge compressor and a bottle with emulsion, fast, "clean" and transportable. I want to put one on lathe and one mobile for drill and mill. They cost few bucks, the hose alone, here in italy cost more than 2 of these components shipped. I want to try  :Roll Eyes (Sarcastic): 

The Lc200 meter is quite good! the plastic case is something re used from another circuit, it shows 9v dc instead of 5vdc , power on off button is marked "ac- dc", no included instructions or manual, but at least it's good at measuring components. A strange thing I saw is the choice between high and low capacity button. The threshold is 1uf, I see that in this range the circuit is in low cap mode, and not in high as manual says. 
Oddities aside, once I understand how it works, it gives nice measurements! Every start I check if resetted to "0", both for capacitance and inductance and then try measure.
in few words, not as immediate, but for the cost and above all for the precision is so good. There is anothe one better meter, but price is too high for my pocket, and for my usage.
here the manual:

http://mpl.jp/lc/LC200A%20%20EN%20V5.0.pdf

I tried different componenents, the measure of coil is so accurate that it's the same value I tested at coils factory with professional Lcr bridge. Capacitors are close, I was sick from the measured value of a standard mundorf capacitor... it's 10 years old component, I used it on speaker for some test, like other parts, the value measured is not so nice, compared to the name. Maybe it's my cap, or maybe the basic line is not so nice  :EEK!:

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C-Bag (Apr 19, 2016),

Paul Jones (Apr 20, 2016)

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## PJs

The meter looks pretty good for a small price. As for the cap being old and out of 3% tolerance, you also have to keep in mind the meter is only good for 5% at either range of measurement 1-10uf (lo) or 1-100uf (hi). After 10 years it's probably seen its day and been a loyal component! 

Hopefully this will help you dial in the circuit and make sure the components are up to spec.

Nice little mister for ~8 euro. Thanks for the update! ~PJ

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C-Bag (Apr 19, 2016),

rendoman (Apr 19, 2016)

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## rendoman

I sin of gluttony and I blew the ammeter, it was rated 1000v 200ma, with less than 1kv i see fire inside the instrument and now it has the 0 position at 190ma  :Flame:  damn chinese meter! next time i put on negative rail.
... With this I will go to shooting range I will put the meter at 50 meter and try to shoot with 7.5x55mm swiss or 416 rem with scope!  :Roll Eyes (Sarcastic): 
I'm collecting info and measurements at the moment, waiting the frequency counter, but i'm glad to see that aside many troubles with noise and oscillation the sound pressure level is high! Sound is terrible, but volume is so high! less heat troubles, less current, less grid voltage... now i'm one step forward in the right path, light years away from winning. As usual recording microphone of camera is bad.

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C-Bag (Apr 19, 2016),

PJs (Apr 20, 2016)

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## C-Bag

> .. With this I will go to shooting range I will put the meter at 50 meter and try to shoot with 7.5x55mm swiss or 416 rem with scope!



LOL! There has been many a PIA (pain in a**) car, machine, etc I wished to do justice to. Never thought about taking it to a range and plugging it! 

I know the sound is hard to tell with the camera mic but it's crazy how far you've come Stefano! This has been quite a ride... :Popcorn:

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Paul Jones (Apr 20, 2016),

PJs (Apr 20, 2016),

rendoman (Apr 20, 2016)

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## PJs

Thanks for the new Video Stefano. Like C-Bag said; "it's crazy how far you've come".  :Banana Dance:  We've all had mishaps with equipment and maybe shooting them is a good recompense for poor quality¿ I accidentally blew a prized 15Amp "Weston" meter once and haunts me a bit to this day...but it was my bad...just had to move on.

I noticed the size of your plasma and it's related "fingers" without too much gyration. Feels a bit like it's being over driven and may account for some of the tinniness (not just the camera mic). Two things: First is your low filter may be off a bit and generally these devices work best in the mid to high range which is what you are shooting for. Second I would bet there is a quite a bit of ozone generated (careful) from a plasma that large which may not be optimal for a clean output because of the secondary plasma that ozone can create a Capacitance effect (lack a better term). Try looking at it through various color lenses. You can get colored (spectral) film pretty cheaply online. It will help you really see the the frequencies and plasma reactions to the input. Just thoughts!

Thanks! ~PJ  :Popcorn:

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rendoman (Apr 20, 2016)

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## rendoman

thank you very much!
I got a bad news ...
I noticed a fault of the noval socket, after maybe 3\4 insertion of tube it loose strenght. Looking better the lower part peelings off the socket! The fault is of very poor quality of the rivet ( It's a low quality aluminum alloy ). For sure noise and connection troubles are linked to this component. I got mounted 2 of these noval, for pcl 82 and el84. I drilled the rivet, tomorrow I will find some good ones. I want to send a mail to the shop who sold me these parts just to know his position. 
...it's like building a new house, begin to decorate and discover that the foundations are rotten  :Flame:  :Flame: 
I sacrificed a new socket in order to test the goodness of materials... poor poor pooooooor quality!
Hope I will repair both sockets without desoldering the 3 stage before oscillator ... 

Thanks for advice! I have to make some research of spectral and lenses, i never thinked to ozone as an external capacitor.
I'm trying to understand how this plasma runs  :Wink:  , the "large flame" is just for aesthetics (at this point) maximum sound level is obtained with low flame and high audio imput. It's even strange that there is little ozone, only up to flame. I played with high volume for 3 hours but no smell of ozone in small room (4x3m +/-)

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PJs (Apr 21, 2016)

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## PJs

Thanks for the pictures. Sorry to hear about the socket troubles. Porcelain sockets are quite good usually, particularly for higher voltage/RF. From the first picture it looks to have a lot of stress from the wire gauge and components close to it. It's also a bit fragile from torque. A slight over torque from the mount screws can put hairline cracks in it. When I built that HV supply years ago, I used them but found some real nice silicone coated wire to use on it and very carefully torqued the screws. It is quite flexible and holds up to HV and RF. It had much larger rectifier tubes but that puts some strain on it too. Food for thought... :Hat Tip: 

Hopefully your dealer will warranty them or discount some new ones for you.

I used to get optical stuff from Edmond Optics. Here is a link to a handy filter set that might work for you at a reasonable cost. You can also talk to some decent photo shops. They use them for various effects.

Here is a good starting place on Plasma. The links within can lead you into the rabbit hole of "The fourth state of matter" and all that is/has been explored in it.

Surprised  :EEK!:  about the ozone! Good luck on the sockets! ~PJ  :Popcorn:

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rendoman (Apr 21, 2016)

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## rendoman

Hi!
new update, good for certain aspects  :Roll Eyes (Sarcastic): 
I tried to change imput filter at 5khz, nothing happened. The problem imho, is the audio stage. For sure walkman hasn't high output, not enough to drive at maximum pcl82, but the voltage at pentode is still low.
Second trouble, the sound improves quality with some more current then minimum, with actual circuit +/- 1cm flame. Plate is good, but grid 2 (5 watt max) glows red easily, and that's not completely good. Maybe I can improve tuning coils a bit more, I reached autofire but I cannot do miracles  :Big Grin: 
After these considerations, I will build another plasma, in "test" frame. A friend gave me one 813 tube, and I will buy a Gu81 big tube, for sure over powered, but at least strong for my purpose. 
For sure I will change audio amp, I'm studying about El34 - 12au7 tube. 

I'm thinking about the frame, maybe it's a good thing to make a gu50 amplifier with custom output transformer, sell it, and use the proceeds for the plasma tweeter. I don't need more than 1 watt on my horn, it would be another parked component

I post a pic of some night ago, a friend built a big tesla coil, really nice and loud!

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PJs (May 12, 2016)

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## PJs

Thanks for the update Stefano. The 813 is a great tube for this I think, very robust and will handle what you have to give it. Many years ago I had a matched pair of RCA 833's with gold grids I used on a transmitter...that's what the HV power supply was for. Later I traded them for a Diamond Back bicycle for my son.  :Cool:  Wish I still had them as the prices for them now are through the roof. The Gu81 is similar only a pentode. The 12au7 is one of the all time great audio tubes in my book...Think you will be fine with that.

Nice size tesla coil your friend built! Way fun!

Look forward to your next update. ~PJ

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Paul Jones (May 16, 2016),

rendoman (May 13, 2016)

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## rendoman

Hi, small update
I buyed this cheap frequency counter on march 20 (something about 13 euro) , just arrived few hours ago. Very poor packaging, damn chinese seller, poor quality shipping with no tracking number, but al least after 2 months is here. 9v dc supply, I have to make an enclosure for this double pcb circuit. I made a speedy test with the last known coil, tested one month ago with a professional frequency counter Hp (some ghz), I remember the same value one digit after decimal point, that's pretty good for my purpose, I'm happy to have the unit value. For sure there are some powerful mitigations inside the circuit, number are too much stable compared to Hp unit. 
In few words: for 13 euro it's a good instrument, it's rated for 0,5ghz and it seems that it works good. I will make a little enclosure to preserve it from damage

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C-Bag (May 17, 2016),

Paul Jones (May 16, 2016),

PJs (May 14, 2016)

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## rendoman

hi! new little update, not for plasma
I buyed today 2 oscilloscope, the first is a tek with calibration certificate (fresh of one month) and the second an old unaohm. Both pretty good, with probes.
Now I have to study a little how to do measure with high current and voltage circuit, then with rf circuit
Hope I will not burn the scopes  :Big Grin:

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PJs (May 26, 2016)

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## PJs

Very cool Stefano! Glad you went this route as these will be invaluable I think, compared to your frequency counter...although handy. They will give you the advantage of measuring and checking signal quality throughout your system. These are great choices for what you are doing. Is that older one a Unaohm too? Reminds me of my old Eico but has an HP/Tek look to the case of that era.  :Thumbs Up: 

I have an old TEK 2645 4ch analog that was used in a University lab (regular calibration) and almost new that I use for analog audio work. Also have a TDS 320 for digital work...both great and you will get _used_ to the Menu system with a bit of _practice_. I also have a BK 4017B generator that works great for my general needs plus the 4 channel HP8409a I put in the Hawk - DC-600Khz.

Check your probes for quality and any issues with noise...And Definitely ground your probes...You'll be fine! Great find and new additions to your tool box! 

Thanks, ~PJ

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rendoman (May 26, 2016)

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## rendoman

Hi all! 
Thanks to a friend who gave me the 813 tube, I will try a new plasma "on steroids". I got some troubles with current circuit, first of all I think I need brutal power from amplifier. I don't know how commercial (or free schematic) plasma runs with bu208a or small pentode, my prototype with such power doesn't do even coffee :Big Grin:  ! I'm thinking about rebuilding a module with amplifier and modulator ( I think el84 ) and trying both gu50 and 813. Currently flame is good enough, maybe needs a little more driving capability.
I'm thinking about use another gu50 as amp, maybe with an ECC family tube. I need to build a good outuput transformer, maybe 5k from 20 to 20k or a "special unit" anode choke up to 200hz ( 1\5 turns ). I got some different voltages from powersupply, excluding 1100/1200 v I can make dc from 250 to 600v, I have to choose a good load and working point for gu50.
I tried also tek scope (not connected to circuit, frequency counter with plasma on, i post some pictures

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C-Bag (Jun 5, 2016),

PJs (Jul 2, 2016)

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## rendoman

Hi! New update
I tried my new Rca audio generator (nos) with plasma circuit, in order to drive it at full power. 
Things are better! more volume, sound starts from 100 hz. Making this test is annoying, it's better wear ear protection next time  :Roll Eyes (Sarcastic): 
At least now is sure that I have to change both audio amplifier and double (or change) oscillator tube in order to gain more volume and avoid destroying the tube

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C-Bag (Jun 19, 2016),

PJs (Jul 2, 2016)

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## rendoman

Hi
Better quality of sound, video and new pictures!

Audio generator drives plasma at full power, Volume is pretty good now, but I want more
It's funny to see how flame can change of shape and size with volume and frequency. With very low freq you can see the flame is open with multi point, higher the frequency flame becomes sharp like a candle.
I'm drawing a new circuit with el34 and 6sn7, both octal socket, tight and strong.

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C-Bag (Jun 20, 2016),

PJs (Jul 2, 2016)

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## Toolmaker51

Rendoman; 
Guess I haven't looked at this post. Nice shop buddy! 
I don't recognize what brand of lathe you have. I know/ used Cazenueve, Nardini, HES, TOS, Rambaudi and Graziano. That quick change toolpost is what I use. Those widely spaced vee's can really take the power. I associate them of Italian and Swiss design, hard to find here. They aren't impossible to duplicate, that is on the list. They might have been introduced by Enco when they imported good tools [ when no one cared where China even was]. I'll find something I can send on tool grinding. Good choice on convertible mill too. Vertical might be preferred simple setup thing, but horizontal is _REAL_ milling! Is it 40 or 50 taper? You have multi-collet tool holders and rigid holders too?
Photo 6 tells me 'troncatrice a disco lento' is a 'cold saw' = coolant/ hollow ground blade and straight teeth/ swiveling vise [almost a milling vise] and direct drive.
That's a super blacksmith's post vise too. If you're only going to have one vise, then make it a post vise! Flat shear, bender, welders...When Jon asked what your next project was, you could say "Anything I want".

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rendoman (Jul 2, 2016)

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## rendoman

Thank you very much!
it's from few years that I collect old equipment, for two reasons: the first is the low price, and the second is that here in Italy is almost impossible to find a not chinese tool running with home main voltage. Industrial type 380v 3 phases are really expensive. Old shops throw old equipment, with a bit of fortune is possible to find good pieces, I need only patience  :Roll Eyes (Sarcastic): 

My lathe unluckily lacks of the label, I searched in every part but not a name impressed on cast iron. It should be an old " Grazioli Fortuna 150 model " . Base,head and legs are from old type leather external belt but transmission is internal with triple trapezoidal belt and 3 gears. I maybe be wrong, but It can be a lathe of a transition period, maybe 50\60. I Had for very low price from a friend, but I restored many parts like gear bearings, rebuild a shaft of internal auto transmission and other things. Luckily old owner changed some months ago big bronze bushings. 3hp- 2.2kw 3phases engine with 120uf capacitor, run very good with normal 230v monophase voltage, never run hot, even after long use.

Milling machine is a old type Cst, factory is still alive, it is maybe 25km from my town. Morse 2 taper unfortunately, but it's old. I got vertical head and horizontal shaft with spacers and some tools, but I use really a little this. I got a multi collet, er25 if I remember correctly, and a couple of 20mm mills with 2morse taper fixed, imho better to use.

Thanks for the name "cold saw", it was difficult to find the correct name of this machines.
I'm thinking about making a portable table with post vise, grinders and welders, useful to do things in different parts of house, free some space in my poor little garage and provide some tool support inside. I remember the day I buyed my first ac welder, owner told me to see if there was something else I desire, for 5 bucks I buyed the post vise! good times! :Smile: 

My biggest problem is that I need more skills, I'm only an amateur self-taught that try to make things, sometimes good , sometimes bad... like Yesterday, when i do a bad move and I crushed my finger  :Flame:  It appeared a face of my nail! Hope in few days to have less pain

----------


## PJs

Hi Stefano, *Great job getting this dialed in*. Personally I think you are *there* with the power and the 813 (Great old Tube) will be overkill (400W) and may cause some issues with your plasma electrode design and your Horn to handle it. Also keep in mind, your horn will amplify and directionalize the sound you already have...and You already need ear protection.  :Stick Out Tongue: 

Glad you got a frequency generator too...Is it an old Tube Type? It's the only way to really look at the input versus output. 18-20k is pretty impressive but noticed you may have been running it on Square wave not Sine??

I watched the videos a couple of times and not quite sure what to say about the differential flame shape. My gut is telling me it is a distortion at specific frequencies or maybe some type of harmonic resonance/dissonance.

_My thoughts at this point are:_ When I built the Hawk and was testing the transducers I used a program called TrueRTA (Real Time Audio Spectrum Analyzer). It's about $100 for the 24 octave version and used it with the ECM800 mic and a 48khz sample rate, phantom power, mic amp. Newer amps are good to 96khz+ sampling.  :Drooling:  The software has a built in 2 channel scope but what I wanted was the Data in spreadsheet form. Basically I output from the software, 24 octaves by frequency and Db to look at the harmonics and what the real frequency range was based on the Db output...plus the scope has a capture feature. To drive the transducer (your plasma) I used the HP8409a in sine mode with a 4-5 second sweep from about 8-35khz...you can do this by hand with your FG and just sort the data a little finer in the spreadsheet. What this will give you is as true a picture of your input to output (by frequency/Db and harmonics) as is doable without a lab and high end gear. Distortion can be looked at using the scope in the software but it needs to be at specific frequencies, like when you flame splits or within the range you want your "Flame" system to run at.

Another thing to keep in mind with the ECM8000 mic is the distance from the flame but also to shield it from any 50-60hz hum from the other equipment or extraneous room noise. I used a 2m mic cable to keep it away from everything else and on a mic stand to isolate it more. I might also consider putting your glass tube housing on if that is where you are going with it....good time to test that too.

I am super impressed  :Thumbs Up:  :Clapping:  how far you have come and what you have accomplished on this project and can't wait you see you box it up for use!!! Thanks for sharing all of this with us. 

~PJ  :Popcorn:

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C-Bag (Jul 3, 2016),

rendoman (Jul 3, 2016)

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## rendoman

Thanks to you PJs! It's a pleasure to read your advice!

REW - Room EQ Wizard Room Acoustics Software 
I tried this free software, before that my soundcard decided to explode  :Frown:  . It's easy to use and so good. 
This is the graph of my horns + sub (without tweeter ), that's my last measurement, the day after boooom  :Big Grin: 

  

I buyed from ebay auction this old rca audio generator, all tube circuit, new rca tube. Maybe I should clean with some dry spray cleaner potentiometer and rotary switches, more i use commands, better the sine and square waves are, maybe some oxide inside. 

  

You touch the problem with flame shape  :Roll Eyes (Sarcastic): 

I tried measure amplifier with oscillator on, it disturbs too much signals, after all it's a strong rf emitter, then I decided to unplug kv and regulator power supply, I only kept the 300v anode for the first part of circuit.
With amazement I discovered that I got troubles with this stage. I havn't found the reason why things happen, but this stage has an incredibile gain, with very few turn of imput potentiometer distorsion raise quickly.I got some doubt about potentiometer, I've never seen a pot running so strange. Circuit should be "easy", I will try triode connection instead of pentode, maybe the gain is really too much.
I'm thinking about how to find the right way to determinate which load can be good to drive oscillator, now, even with 3w output pentode, raising the voltage gain seems not touch the volume of sound too much (over the threshold). Maybe I need more current from amplifier than voltage, current that I can find with el34 tube, or maybe trouble is elsewhere :Frown: 

In this 3 picture little curve is imput, 0,5v\square div, than 2v imput. Nearly full closed pot, 5v/square 2ch at output from pentode. Even with signals under volt distorsion raise quickly and volume doesn't change. sorry I don't remember the frequency, something near 500hz maybe.

In first pic that's the maximum "clean" gain, after this gain raise with dist. Different shape for square wave

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PJs (Jul 3, 2016)

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## PJs

Based on what you said above, the first thing I would do is squirt some cleaner on the FG pots and switches, like you said. Then I would hook it to the TEK scope and run it through the full range (slowly) while watching it on the TEK scope. You should get some indication of any issues with the quality of signal out. Also I wouldn't waste time on the Square wave at this point. It will give you some clues later but not necessary to diagnose where the issues are. If it's clean Sine all the way through you should be Ok to step 2. If not, note the frequencies where it distorts or has sudden drops/increases in amplitude. Another thing with older equipment like this is sometimes the solder joints get a little cold or corroded. Just reflow them and try again.

Next is the probe of the scope to the input of you preamp and its output all while sweeping your FG (if its clean from test/repair above). You will probably notice some slight degradation of signal quality as you move through the amps and to the coil...and you can look at your Real Gain levels and Q.

I didn't notice any new Faraday cage in the pictures like we talked about and that may be contributing to your problem hooking the scope...Or it might be an impedance problem loading from the scope/probe. Do your probes have a 1x/10x switch? Might try the 10x if you do. If they are only 1x it could be part of the problem you are seeing. I see no issue with measuring the KV measurement even at the RF with the TEK scope, but I don't know that scope very well. The TEK is a 60mhz...so it should handle your stuff fine. The probe may also be tired or have slight cracks in the housing? Also unloading the KV for measurement may not give you a real world look, being unbalanced.

What kind of Pot is on your amp - wire wound or carbon, and what kind of volts & ma (watts) is across it? A wire wound on a circuit like this may give you some inductor type issues particularly at the bottom end, by taking on some of the spurious emissions going on in proximity. Might try a quality carbon pot to see if it's any better.

You may have some issues with impedance matching throughout or maybe some distortion issues in the circuit, but I thought what I heard on the videos was pretty good over all with only some minor glitches going up the scales. 

Like I said way back in the thread...be as methodical as you can, start at the input, look at and solve one thing at a time, Document the problems and fixes as you go, then to the next till you get it the way _You_ want it at the plasma end!! 

What you've done here is remarkable and really hasn't been done in years except for a few wild and crazy guys out there/here who like to Finger it out and make it work. Again, Great Job...Diligence and patience will pay off.  :Hat Tip: 

~PJ  :Popcorn:

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C-Bag (Jul 4, 2016),

rendoman (Jul 3, 2016)

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## rendoman

Hi! 
I tried with tek scope, sine is pretty good and clean, output is pretty high voltage. There is also a "line freq" output asjustable up to 6v (don't know what it's for) 

That's a pdf of manual found online
bama.edebris.com/download/rca/wa44c/wa44c.pdf 

Inside of rca is pretty new, i clean only with air, for sure cap are vintage, but seem good, I don't want to change every cap now, instrument is running well imho.
I will try tomorrow to check "preamp"only, and maybe connect triode instead of pentode, gain and power will be less. Probes are all 1\10x, checked with trimmer. Unfortunally I never made faraday gage, because I'm always undecided with new frame since I will change 80 or more % of circuit and I will need more space. I'm thinking to try a light alu grid as gage, just for test. Trouble is that oscillator is strong enough to disturb scope even with metal screen ( I tried with a solid brass panel in front of coil, something better than nothing, but circuit is still critical, maybe I will need some bulkheads between sockets.

Potentiometers are 2w carbon, chinese unfortunately. 100k log for audio. One things not so good is the load of pentode, a 20w resistor, instead of choke or output transformer, for sure it converts current in heat like candies! :Big Grin: 

You're right, it's time to be methodical, I need to check every single part and optimize. 
I will use 813 as experiment with external socket, but I don't think I will use in normal operation. Too expensive imho, with the price of one tube I can buy some 20 gu50, maybe I will parallel output... thoughts  :Roll Eyes (Sarcastic): 

Hope to post some new good updates!

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C-Bag (Jul 4, 2016),

PJs (Jul 4, 2016)

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## PJs

Hi Stefano,

The FG looks pretty good on the inside but how did the signals look on the scope? Did they jump in amplitude or distort at any frequencies? Wouldn't worry about the SQ wave stuff as the manual states it isn't that good and slants, but good for quick checks...so you would have to compare before and after to really get any kind of clear picture. 

One thing I noticed in the manual for the FG is the impedance and the ("Limited to"  :EEK!: ) .25% THD. It's old school and built like a tank, which I love, but for modern audio...its what you have so keep it in mind. 

Pg 7 shows it to be for a 600Ω resistive load for DBM. Pages 8-11 have good procedures to find out the impedance of the system, DB/DBM, the freq response and IM distortion...All good simple hookups and tests. The voltage out should be Ok (8V RMS) for your amp but figure max input for your amp and hold it just below that. Also in the manual the multiple warnings about connecting around the B+ is a good Warning...you will pop some components if not careful.

For a temporary Faraday you can use Al screen door material. Keep in mind it may become charged so make sure its grounded well in several places. Copper is always best and should be porous Screen or perf metal. Some older computer cases have some copper shielding if you can find an old case somewhere with it you might be able to salvage enough from it. MY old Dell XPS had a lot inside with nice finger grounding strips. Wish I had saved it now.

The Pot should be ok. As for the output of the pentode...Maybe you could devise an LR for it...but would be much better to use an Xformer if you can scrounge one up.

Personally I think you will be throwing too many variables into your _working_ circuit by building something new with the 813. Again, You may be pretty close to the power you need with the gu50, imho...multiples in // will add other issues in matching impedance's and outputs with out buying matched components. 

Please be clear these are Just my opinions and observations...it's your project and you have done Very, Very well so far.

Good luck and may the Force be with you.

~PJ  :Popcorn:

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C-Bag (Jul 4, 2016),

rendoman (Jul 4, 2016)

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## rendoman

bad news today  :Flame: 

I tried to measure both first stage gain and second one. I switched between pentode and triode connection, I changed from resistor load for pentode to output transformer.

summing:

- first stage voltage amp (little triode of pcl82 tube) imput 820mV for maximum voltage gain of 50v 

 
 

- output stage triode connection , imput from generator (I will measure this a 3rd probe even from first stage) max 360mV for 114v output

 


- output stage pentode connection , 244mV for 136v output



Clean limits, after this threshold curve become bad.

I tried also measure with output transformer and speaker - 9,1 ohm resistor ( I didin't have 8ohm at home ), output voltage is really low, under half watt in "clean" curve, I settled tek scope to ch1-2 rms voltage. Anode voltage is 310v, I'm thinking about something happened to catode resistor. I need to focus and think what happened inside circuit.

I put x10 probe (x10 key on tek display) on pentode point, 1x on low voltage signal
I think I'll check every component, cap, resistor, socket. I will be ignorant, but the p-p power should be max voltage output (undistorted) / load resistor in ohm, maybe something near 0,2w, Who has eaten the other watts?  :Lol:   :Lol: 
I will find an answer!

funny picture with ear protection



Here a small noisy video, at the end you can see the sine changing

Little edit, I missed one part of formula, power is 1,5w in triode, not 0,2. power is V2/r or R*I2 or V*i

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Paul Jones (Jul 5, 2016),

PJs (Jul 4, 2016)

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## PJs

Hi Stefano,

You definitely have some distortion and clipping going on from the pics and vid. Unfortunately I don't know your schematic, nor what you are measuring and where, so it's hard to make any kind of educated guess.

From the video it appears that anything above ~400mv (input? from FG?) and 120-134V (Output?) is were things go wonky. Is this the preamp stages and the pentode goes to the GU50 as a final stage? It also tells me your gain is way more than you may realize which always leads to distortion and clipping.

One thing that comes to mind is the cap between the triode/pentode may not be happy or proper. Specs for the PCL82 say .02 & .025pf. Also note the Peak Anode voltage and currents for the Pentode section...If your gain is too high it will lead to saturation and cause the plate to glow and deteriorate the filaments. Are you running the filaments on AC or DC?

Here is an old cut sheet I found for the PCL82. I assume you built the amps and coupled them around these specs??

A bit in the dark here to help any, but it does come to mind that your sound is _pretty loud & clean even at the levels below clipping/distortion_....even with the speaker hook up instead of the plasma. Glad you found an xformer. Also Not clear from above about the 9.1Ω Resistor with the speaker...series-//? Seems to just add a resistive load to the inductance of the speaker??

Thoughts... It's not always about power, but efficiency is king in my book. Look at the efficiency of the old ESS Heil AMT 1b's. 1W input gets 90db at 1m!!! Even though they will handle 375 watts, not sure you could stay in the same neighborhood at full power!! Mo-Power will give you cleaner sound at the clean operating parameters of your amp but anything after 90-100db is a waste in my book. Adding your horn to the plasma will give you even more sound pressure.

Thanks for the pics and vid...

~PJ  :Popcorn:

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C-Bag (Jul 10, 2016),

rendoman (Jul 5, 2016)

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## rendoman

Hi
I'm trying a different amplifier with 6sn7 single ended +el84 pentode. I built the circuit in rapid mode, on the table. Unfortunately I havn't 5k output transformer (only 2,5k), nor local shop has 20w 5k resistor (yes, here the quality of the shop is everyday worse!).

few words about circuit, tomorrow I connect the amp to the plasma and see what happen. Compared to old pcl82 amp this new sound better and louder. I think I need to check every stage but at first sight with same clean 0.2v rms imput I got 5 volts good output, it's more than 2x old amp (clean 2,5\3w). If I close an eye I can run circuit up to 9\10v output with some distortion, but still acceptable (5/6w). Leaving out the measures, connecting a speaker to outpu,t sound is really louder, and that's what I need in order to check spl connected to flame.
That maybe only an experiment, soon I'll try El34 tube, maybe in the same good octal relais socket, maybe the final tube I'll choose

Good thing, despite long cables and chaos, no hum, buzz, or strange sound!  :Big Grin:

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C-Bag (Jul 12, 2016),

PJs (Jul 10, 2016)

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## rendoman

New driver is better than the last! Power is double, with better sine. Volume is loud from speaker, and even from plasma flame. Maybe a bit more power can help, but even now is good. 
I tried just for curiosity this amp with my horn, it sound really good, even with a poor output transformer (frequency range between 100hz - 20khz), but I see too much power for my speaker, I think max 1,5watt can be optimum.

New attempt contemplates EL34, in pentode should give 11watt at 10% distortion, with 0,45v imput, practically double than now! 

Single ended 6sn7, only use triode used. 300v
Imput under 0,5v rms, 7v ouput with I think good curve shape
  

El84 pentode connected, 300v. Good voltage gain, I tried taking signal from output transformer + load it's nearly 2,5 watt very clean, some 5watt with little distortion

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C-Bag (Jul 10, 2016),

PJs (Jul 10, 2016)

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## rendoman

I hate brass, in every shape  :Flame: 
Have to sharpen drill bits better. Maybe I should also take exemple from this fantastic forum and build some clamps - boring head, mine are bad  :Roll Eyes (Sarcastic): 

This is what I thought when I said modular frame Yesterday. Actually I need to try many configurations, with different tubes, that's why I prefer to make single solid brass (can be a definitive way) individual sockets. I think I will add a fast mammut connection or something similar, plus a spike each for gnd point. 
These single frame can be mounted on columns or just for prototype with long allen bolts. I need octal, gu50 and maybe one noval frame.
In the future, for sure, I'll build a planar chassis drilled as base, good to mount single modules. I'm thinking about building single cells shielded, easier to build and to control, above all RF power unit, that clashes with everything :Big Grin: 

As planned, old first tubular frame will be reconverted as home for my old ecl82 amp ( 2 noval sockets ready to use, enough space for my big diy output transformer, choke and maybe a regulated Hv psu with gas regulator ( 0a2 and 5651 maybe ). The front nice panel in polished brass have a pot for volume, 2 switch for filaments and Hv and I connect ammeter just for appearence, I don't need to know how much current flows in this circuit ( fortunately ). I have to find good ammeter for plasma, I will connect them on ( - ) rail of psu, last time I connected 1kv (+) at 50ma it burns like thermite  :Wink:

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C-Bag (Jul 12, 2016),

PJs (Jul 12, 2016)

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## Toolmaker51

Fun to read, no clue as to what's going on. Could be Trabant turn signals for all I know. Definitely not one of my languages, that's certain!
Toolmaker 51

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PJs (Jul 12, 2016),

rendoman (Jul 11, 2016)

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## rendoman

You're right, it's a strange equipment this plasma speaker!  :Wink:  
I added a small noval frame
I'm thinking about using this small frames covered with perforated steel, in order to avoid Rf and disturb. It will be a difficult work to make a "nice looking" frame. any good idea?

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C-Bag (Jul 12, 2016),

PJs (Jul 12, 2016)

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## PJs

Hi Stefano,

As far as the faraday cage goes, like I said you could use screen wire as a temporary for testing and it will form easily. If you are going to use perf metal, I would probably cut squares then cut the corners out. Again, copper would be best but with Many Grounds to the chasis!! If it's thin enough you can form it in the vice over a piece of wood cut to the right size square of the bases and just fold it and tap it with a soft mallet to square it up. Don't forget about spring back on your mold size. 

Not sure on the under chassis? Might take some standoffs from the brass down the height you want. You can form/wrap some aluminum sheet (.050 or .063 -2-3mm) around a form and bend tabs over to be able to put the standoffs into. Probably want to leave the bottom open like a normal chassis for air circulation on the sockets, resistors and caps.

I think individual cages will be good for testing and isolation but the feed thru's for the B+ will be a Pain to do cleanly, and will still end up with some spurious emissions. But at least you can test. With the modular design you may be able to put a larger perf metal canopy over the tube parts (modules) and maybe over part of the plasma electrode too once you settle on a configuration.

Sharp tools On the cutters for brass...and HSS works best IMHO. Think I put a link in somewhere back up the thread for angles and such. If you watch Chris from Clipspring...he does amazing work on brass and his clock pieces...all with HSS tool bits.

Good luck...look forward to what you come up with.

~PJ  :Popcorn:

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C-Bag (Jul 12, 2016),

Paul Jones (Jul 13, 2016),

rendoman (Jul 13, 2016)

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## C-Bag

> Fun to read, no clue as to what's going on. Could be Trabant turn signals for all I know. Definitely not one of my languages, that's certain!
> Toolmaker 51



Me neither T-51, but it's been some deep wizardry going on here and all us mortals can do is  :Popcorn:  

I never would have thought you could get audio out of a plasma flame, but then again I'm stumped by my new cell phone. Doh!

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Paul Jones (Jul 13, 2016),

PJs (Jul 13, 2016),

rendoman (Jul 13, 2016)

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## PJs

> Quote Originally Posted by Toolmaker51 View Post
> Fun to read, no clue as to what's going on. Could be Trabant turn signals for all I know. Definitely not one of my languages, that's certain!
> Toolmaker 51






> Me neither T-51, but it's been some deep wizardry going on here and all us mortals can do is  
> 
> I never would have thought you could get audio out of a plasma flame, but then again I'm stumped by my new cell phone. Doh!



Ha Ha guys...busted me up with the Trabant reference and I'm also stumped by these new fangled phones...and mine's an old Note 2.  :Head Scratch: 

The wizardry here is that Stefano has pulled off what only a few have done in the past and on a cheap and cheerful budget! Only a few Audiophile versions are out there and they are Big Duckets...heart stopping actually. Top ratings in my book and trying to help as I can, but had to set the way back machine between 3-5 decades ago when I worked with tube circuits...been a fun journey though...and he is very close!!

Way to go so far and Keep it up Stefano your almost home!

~PJ  :Popcorn:

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rendoman (Jul 13, 2016)

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## C-Bag

Yup, I agree Wiz.

You go Stefano, you gotta be close.......

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PJs (Jul 13, 2016),

rendoman (Jul 13, 2016)

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## rendoman

Thank you very much! your compliments give me strength!  :Thumbs Up: 
I hope in few days to finish the new sockets, I want to double the oscillator tube, find new equilibrium coils, new powerful amplifier with el34 and maybe some snake oil! 
see you later!

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PJs (Jul 13, 2016)

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## rendoman

It's not day!
After an evening trying to destroy the old plasma and rebuild with new small frames. Now I got 2 oscillators in parallel, let's see if can be a good thing!
I accidentally swapped 6,3 with 12v filament and in a fraction of a second the last el84 (JJ, maybe are made of sugar  :Flame:  ) of 3 tube cascade I broke the filament of this new tube ....
Tiny flame for one second, really high blue from new gu50tube (maybe some air inside like first time of the other tube?)
I left everything on the table and came to sofa, it's useless to change coils now with tired mind, maybe Tomorrow I 'll find a good Equilibrium between coils! 

For now, the only vantage is that this setup is so handy! Long wires for sure, but at least funny to change parts in few seconds!
I post some picture of the new setup, the small frames are good, but I'm not satisfied of polishing... 
Only good news I have is that I found a nos rpm meter, old mechanical type Veglia Borletti, but don't know for what kind of motorbike can be!

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PJs (Jul 16, 2016)

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## PJs

The tube bases look pretty good to me Stefano. To bad about he 6.3-12V mess up. Happens to the best of us...done that one my self and because I was all speed and no control...or double checks!  :Smash:  Hopefully you can get a good deal on some replacements.

Not sure how you are hooking up 2 Oscillator circuits or if it will work...I'm assuming parallel some how to get the watts you are looking for? May have to futz with components if they aren't a matched set. How are you feeding both from the EL84? My ears are buzzing just thinking about it...

That tach probably came out of a Guzzi or Duck...but based on the red line probably a Duck. Nice find though!

Hope you got a good sleep and have better luck next round. 

Thanks for the update, ~PJ  :Popcorn:

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rendoman (Jul 16, 2016)

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## rendoman

Thanks Pj!
It was not easy but somehow we made it to fire plasma!

Obviously I have to setup circuit "as new"
This circuit is Always possessed by the devil  :Evil:  , brass socket are not grounded (now), if you put a wire from brass, and other tip in free air (aiming fire coil) flame x10 size with no movement of flame potentiometer, It's sign that something in circuit is not in correct place, above all synch of coils with air.

Strenght of field is great now, neon shows more light, and turns off in 60cm. 
I have to study something about parallel oscillators, I see a great difference between emission of the 2 tubes in overdrive condition. Only one become bright red (see in first picture). I have to measure how much current each oscillator draws, at first sight I think we're close to half ampere at kv, seeing the color of anodes.

Currently I'm driving both with tiny el84, (with no sound because I broke one), DC voltage on G2 of oscillator is strong enough to keep these grids sshiny red, I'm not so sure that with new el34 amp the little el84 can keep the high AC signal from amplifier + DC ... I build 2 octal frames (plus preamp on relè socket for now) for this reason, 2x el34.

I noticed one thing, russian socket of gu50 have external pure aluminum frame, temperature of the thick brass frame is barely touchable even to the corners, I think something about 70 degree C. Not a problem for anode, that could be made from zirconium (I remember correctly?), and maybe that can help retain temperature to help oscillators.

Bad note, as usual I'm a donkey and I like to pull circuit at maximum... I melt the tin weld of copper tip! that means that the lower part of tip reached about 200°C, That oblige me to make a mechanical connection with tungsten rod (as first setup)

Now it's time to try this new way! 
Don't know why frequency counter shows 12,5mhz as usual from coil, but 100mhz near oscilator tubes...maybe it takes some eddy frequencies.

With flat copper damaged tip flame is really large, not so high, but round, I want to see it with sharp point :Roll Eyes (Sarcastic):

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PJs (Jul 18, 2016)

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## rendoman

Because we love tubes, like women: hot !!!  :Roll Eyes (Sarcastic):   :Roll Eyes (Sarcastic): 

Circuit is always strange, it runs only with a short wire connected to right metal socket and no contact on other side. Temperature of frame is high as hell running circuit hard, it's really difficult to touch brass.
At least now the 2 tubes runs togheter, with no more Chernobyl nuclear reactor 4 effect (maybe the air inside the new is finished?). 
I'm not convinced that this path should be good, The only positive thing I see is that circuit is less sensitive to rf coil value. I see more power, but not so much to raise glasses.
Strange thing, Ceramic cylinder is a bit conductive, in picture you can see a spark from ground wire. Maybe is dirty, or maybe it's like old bakelite socket that metallized with time?

I want to change some other parts, I make calculations for gu50 amp and el34, 18w vs 11w both in pentode, 6sn7 driver, maybe in srpp, now in single ended can pull 7volt undistorted, not enough to drive gu50. 

... let's see in the next days!

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PJs (Jul 19, 2016)

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## PJs

From what I saw in the previous post, I would doubt you are pulling 500W (.5A @1KV) from 2, 40W tubes...otherwise they would be melting the plates, grids, filaments and likely the glass...and you _will_ Ruin your nice porcelain socket! IMHO you are pushing the tubes way tooooooo hard from the Pics above. Keep in mind that with the plates glowing deep red you are giving of pretty good amounts of infra Red and some X-Rays...Not good! One thing about tubes is the more you push them, they begin to break down and become LESS *Efficient*, with a much shorter life span. Properly breaking in a tube will give you the best results and last, usually longer than the life spec.

As for the 100mhz (if it is accurate) it may be some harmonic you are seeing because of the ~30mhz oscillator and it may have other spurious emissions you are picking up from the surroundings and the way the table is laid out...not sure I trust that digital meter at those frequencies.

I can see RF burns on the coil ceramic. It will be metalized and throw off your the whole kit and Kaboodle of frequency/mH/resistance at these frequencies. Might try cleaning it with Acetone but be careful of your wire...it'll take the coating off in a heartbeat.

The flame definitely looks better shape and size.

Honestly Stefano I liked it much more when you were working towards the goal of an audio plasma speaker with a custom cone. This is starting to feel like a 5KW tesla music modulator, not an Audiophile Plasma Speaker. It is fun to push the envelope sometimes but it is dangerous...even with what you are working on and do Not want to see you hurt, nor discourage you from reaching your original goal!

*Efficient*, *Efficient*, *Efficient*, *Efficient*!  :Smash:  Your Call!

Till Then,
~PJ

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C-Bag (Jul 19, 2016)

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## C-Bag

Wow, u da man Wiz.......

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PJs (Jul 19, 2016),

rendoman (Jul 22, 2016)

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## rendoman

Hi again!

Pj your right, It's better I focus on audiophile plasma!
But the more I experience, the more I realize that I know nothing about electronic  :Hat Tip: 
Summing in few words: I'm experiencing different kind of circuit. With the precious support of digital scope, some softwares and some old papers I'm ironing out the kinks.

The reason why I'm chianging so many parts, working points and circuit is that I got really low volume, not enough to match a good speaker.
I tried to double oscillator in order to have a better flame, running at low, mid, high, and over range just to know how circuit works. At full power of double oscillator, another amperometer connected showed something less 0,5A at 950v with load, something more than 400w. Thanks russians this tube is made in hell, with nickel - zirconium plate is strong enough to survive these test lossless.
It's clear that I can't run during normal use of tweeter at red plate, and maybe it's not even necessary. I saw that 1cm flame (minimum now with 60v dc on g2) should be enough.

Good thing is that from oscillator I think I took everything I could, well tuned.
Bad thing is that Whole rearguard is inefficient. I'm focusing on amplifier, I Did different setup:

- Pcl 82 triode + pentode 1.6 / 3 watt

- 6sn7 + el84 2.5w undistorted, 5.5 w max (I think I will make a new amp for my horns with this setup, it's really better than my ecl82)

- 6sn7 + gu50 at low voltage (300v - 160ma), I tried both single ended driver and srpp, completely unuseful!
Poor anode amplitude, poor power output. 
I tried this night using a pcl82 in triode to drive this tube, 3,5w undistorted, or with both eyes closed some 7w... huge power consumption for nothing. 
I think this tube need more voltage and powerful driving, I'm even more convinced on el34, with good full datasheet, not the toilet paper of gu50.

I got a strange feeling about modulator el84, imho this part of circuit is making a big mess. Don't know why, actually, but I think there is something strange that blocks audio power. I'm studing a better modulator, maybe high level mod? 


nice picture of a plasma acting like a tesla coil, unfortunately caused by some ground issue
 

soft mess on the table


Output of gu50 amp, pcl82 driver stage is strong


Gu50 anode amplitude


Little monster, with no hum

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C-Bag (Jul 23, 2016),

PJs (Jul 23, 2016)

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## PJs

Thanks for the update Stefano. I get it that you are somewhat of a novice with the circuits but you _have_ achieved success with what you had set up imho. The "Loud enough" is hard to quantify for me and still think you have some mismatch components in the circuit. Here are a few more thoughts from an old fart that hasn't done any of this stuff in 3 decades.

Old circuit.
1. As I mentioned in our PM's the 22nf cap between the output of the PLC82 and the input of the EL84 is WAY too small. Try a .01uf and move up to maybe a 10uf or bigger. There also needs to be a pull down resistor....see Pg. L of the data sheet. They show a 35uf and 5.6k for the output circuit in the diagram of the curve chart. Also on the EL84 that R network from the plate to ground and G1 with the 180k, 100k pot, 22k and the 1k off the center of the pot seems like it will kill what you are getting from the PLC82...especially with that 22nf in there, particularly your higher frequencies. You want to hold your G2 (EL84) to ~250v @ ~10ma and the 180Ω seems about right. Your output on the PLC82 needs to be about -7.3V at G1 on the EL84 but it feels like the cap and R network are giving you something else.

2. I still don't understand how the cathode (EL84) to G2 (GU50) works to drive the gu50 as a modulator with G1 being your oscillator. Typically you would use an output circuit between Plate and ground to drive the GU50 (G2) as a modulator carried by the oscillator. This also may be some of the issues you are seeing with the modulator circuit...its basically open and dissipating its output through the R network above, to Ground.  :Head Scratch:  According to the "toilet paper" G2 on the Gu50 should be ~250V and you are pulling it to ground through the cathode.  :Confused: 

New circuit...
I like the idea of the 6sn7 feeding a push pull pair of EL34's. That would give you 25W available if necessary into the GU50 as a modulator..._if_ you still want to use it as an oscillator/output. Honestly, I think 40-50W is plenty with your Horn, _if it is achieved cleanly between each circuit_. I would build your 6sn7 circuit drive it with the Analog Frequency Gen. and dial it in until you get clean output at around 5W. Then build your EL34 circuit to match the output of the 6sn7...and test them with the Generator till you get clean output at around 15-20 watts...more than enough to drive G2 of the Gu50...probably going to need to tone it down and not cause distortions on the output of the plasma.

I haven't spent a lot of time on this new circuit but those are good solid tubes for your application...and good sheets/circuits available.

S'all I got for now. Good Luck!!

~PJ

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C-Bag (Jul 24, 2016),

rendoman (Jul 24, 2016)

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## rendoman

Hi all
This post is really useful as a diary for me, all the changes I made are here! And it's Always a pleasure to show you some nice picture.

It's difficult but I'm trying to follow PJs way, more method and focus on problems.
Few words about last changes, I tried to focus on power part of circuit. There was some issue related to a wrong choice of tube, that's why now I got 2 gu50, one as mod and one oscillator. 
Things are really better now, no more red grids, light red plate with full output and lower consuption of current.

I'm waiting a couple of el34 tubes, I have to raise power and amplitude from amplifier now, and maybe I will be ok in principle, last adjustments will be done with final frame.

Sound is loud enough, even without horn. Combustion chamber + horn will be necessary in order to erase ozone.
See you on the next episode  :Lol:

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## rendoman

New small update, after august 
I'm building a new frame, bigger than the old one. The reason is that I need more space for tubes and rest of circuit. I'm also converting the old frame to fit my tube amp, keeping brass panels and general layout.
This time I will cover the tubular frame with steel plate.
I also rebuilt circuit in order to run el34 tube, I'm undecided with first gain stage, 6sn7 or ecc82 - 12au7, I got both of them and performance are close.
I hope next week I will receive new tubes and sockets!
Let's start again the project!

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PJs (Sep 9, 2016)

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## PJs

Nice looking frame Stefano. Figured you were pondering where to take this great build! Looking forward to whatever progress you make on it. All good choices for the first stage just depends on what filament supply you have most of, I think.

Keep on Keepin' On...Thanks for sharing, ~PJ  :Popcorn:

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rendoman (Sep 10, 2016)

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## rendoman

I'm trying to study parts position, tube sockets grouped, output transformer close to el34 amp tube. 
A bigger horn compared to old one, because frequency range is increased. I will put separated gnd for circuit and frame.
I want to braze with brass the edges of panels, just to give a better old - steampunk look, I'm not sure, that's only an idea!
I have to wind output transformer, dedicated with low inductance, in order to reach high freq. Lot of turns by hand.... infinite work

I have to think about main coil, I got problem of heat and temperature. I have to find, or make a couple of support. Tin-lead melt at 180°C , with 5cm tungsten tip at full power I melt the welding in few seconds. A mechanical link is good, but I'm not sure Teflon can keep this temperature (even if tweeter will not run at full fire Always), and I don't know how to model ceramic... I Have to think about this problem

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PJs (Sep 15, 2016)

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## PJs

Looking Good Stefano. Layout is one of those things on a project like this that must take a lot into consideration like close coupling, isolation, grounding, spurious emissions, let alone all the mechanical's...etc. In this case the biggy is HV AC/RF to DC to Audio...and Ground planes. The other is porting thru a Faraday cage. What you are doing placing the actual component on the chassis is the best way to flush out the puzzle of this type. Take your time and go to that Zen place with it...eventually its cork _will_ float.

Did you measure these temps? Silver solder would work up to about 500Cº. My suggestion for the Tungsten electrode would be to make a mechanical connection. Maybe a double ended, machined brass ferrule with minimal (slip fit) for the tip and conductors and maybe 12-15mm diameter so you can put in 2 set screws (3-4mm?) for each end. One set screw (socket head dog point or cup, type not cone) would work probably, but 2 better @ 60º. The key would be to keep it small diameter as possible to keep the spurious emissions down in that area. As for a support maybe a rectangular block of PTFE if you have it...it's should be good up to about ~200Cº. Maybe 2 square porcelain standoffs with a smaller block between them for support¿ It would also depend if you will use the ozone isolation glass tube. Alignment to the cone and some kind of fine tune adjustment would help to dial it in.

As for the coil, your porcelain tube can use a mechanical half cup type connection through the existing holes at each end and supported by some of that green stuff or UHMW blocks or a ring?? Good to ~200Cº...it should never get that hot...hopefully. Make sure to clean all the burns from it.

Like the Steam Punk idea but don't let it dictate what it needs to be electronically. 

Thanks for the update! ~PJ  :Popcorn:

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rendoman (Sep 15, 2016)

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## rendoman

Thanks for the advice! I will think with fresh mind this time the layout!
I finished the output transformer - anode choke for audio amp inside plasma. 3,5K load, 100ma, high freq cutoff, low inductance and resistance, hope it will run good with el34 tube. I'm searching info about this type of loading (without a real load on secondary winding)
Saluti
Stefano

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## PJs

Looks like a Nice, clean winding job. Is that Teflon around the outside? The EL34's look great...Nice find! Thanks for the update. 

~PJ  :Popcorn:

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rendoman (Sep 21, 2016)

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## rendoman

Around the outside I used a strong paper used for electric motor, should be mylar paper according to old man who gave it to me. Very rigid and in various thickness, I used 0,2mm. He gave me also a very nice mylar scotch tape, close to perfection to keep winding in position. Unfortunately calculations foresaw slightly different values, I got maybe a bit low inductance and resistence as anode choke. Some manufacturer has anode choke of high impedence (80\100H for 10-20hz use), I don't need low cutoff frequency, but I got some doubts about this. The good thing is that I got space in bobbin, I can wind maybe 5x of actual turns, and maybe this time, with lathe, luckily is only an inductor  :Smile:  obviously I will try to do by hand

This El34 tube are made for Langrex, a uk company of tubes and electronic parts. For sure made in Cina by Shuguang factory, quad matched. Imho this production is a "good selection" of el34, maybe matched in factory during test. I would like to think so  :Big Grin:  . Even if they were only fables, 15 euro shipped each tube is a good price. In my city shops I've seen similar price range tubes ( chinese, JJ, elettroharmonix ) from 22 to 45 each, even on ebay price are good.

I try new layout, I'm trying to make a good use space. For final version, no potentiometer, no volume, and switches in the back, in order to not keep around half meter of 6 cables for power supply. I have to find a good amperometer and maybe a voltmeter till 2kv, not easy to find, unfortunately! This evening I made a couple of support for power supply and Hv unit, to Mount close to sockets.

I changed Gu50 position because heat, and thinking the worst scenario, the replacement of final oscillator tube with one of a higher class (Gk71 - 813 for example). I really want to keep gu50 in circuit, because it's good, but you never know... better to get hands on  :Big Grin: 

I'm not sure if it's better to use milling machine to open large drill on thin steel, or maybe use the oxy torch, for sure a fast work!

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## PJs

Nice the old guy gave you some paper and Mylar tape. The paper, if made for xformers will be fine with a layer of tape over it. I know you are winding this yourself and it's a pain, but you can change your inductance with the gauge wire...but still depends on the frame quality, laminations & permeation you have. 80/100H does seem high but not sure in this case either.

Really good prices on the EL34's especially if they are Matched...wouldn't count on them being perfectly match but close would be great for this stage.

Glad you are shortening your wire runs it should really help in the isolation. Perhaps you could run the low voltage stuff on one side of the frame and the higher on the other. What is the amp meter for? For the amp meter you can always use an external shunt with an MA meter. A 2kv voltmeter is a bit more tricky to find but again you could build a small external voltage divider circuit...in both cases you'll need to rescale the meters and they will lose some linearity.

I'd think the mill would be better for the larger holes, but you need to work on the cutting geometry of the boring setup you have...although you might find a hole saw (~$15-20) the right size and go slow (peck it) with lube. Give yourself plenty of clearance to the hole in your brass plates for wiring and isolation. To me the torch would mess up your pretty work so far and need a lot of clean up. 

Good progress! Thanks ~PJ

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rendoman (Sep 22, 2016)

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## rendoman

I'm trying to understand how plate choke runs in circuit, I read many things, but this site puts confusion in ny head :Big Grin: 

Magnequest Tech: All choked up on Grid and Anode Chokes

Reattanza induttiva online fast calculator

My need is a 100ma coil , for a 3,5k load in pentode mode el 34. (15 kohm internal resistence for el34 in pentode), 

For sure, normal audio amplifier should reach 20 hz min frequency, for normal operation. My plasma will be start from 1000hz, ideal starting frequency, maybe it can fall to 500hz, but horn becomes big

Magnequest advice is to keep 8 times internal resistence of tube, talking about output transformer, and in the middle of page the formula of reactance. I have trouble understanding this site because data imho are confused

Magnequest Products - MQ Iron Listing/Pricing

Let's take for example BAC80 model, rated 80ma, 50H , 325ohm resistence (same current of my amplifier)
Formula gives for 50H and 20hz freq, 6280 ohm of reactance , that is +/- double than the recommended 3k load for pentode, but still usable as load for the same amplifier. 

According to site, why to 8x the internal resistence of tube? can be a good rule for a low resistence tube, but not for a pentode imho.

Calculaton for my inductor, 3H , at 320hz give me a reactance of 6K, that's double of normal loading of my tube. In theory, if I filter the imput with and high pass with this value, everything should run ok, or I overlooked something?

I think I'll find out soon  :Roll Eyes (Sarcastic): 

Ps: I used oxy torch, and file, because frame was to big to lock on milling machine

Ps2: I'm thinking about data

- 8x internal resistence = inductance es: 8x 15K = 120H (at 20hz)
- my inductor is 3H, reach 15kohm of reactance at 750hz
- if I want to lower frequency, keeping 15Kohm minum, I have to increase inductance at 7H for 320hz for example, or 25H for 100hz.

my question is: why 8x the internal resistence?

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## PJs

Stephano, I feel like I'm back peddling here at this point again. First I don't know if you are changing the EL34 circuit to a single class A or push/pull double...but you said pentode mode so that helps in looking at the curves on the cut sheet. Second you never said what your differential g1 voltage is. Third in your calcs I don't know where you got the 325Hz from but if you put the numbers in the calculator you get 6K-XL...yes. Yes the Ra is 15K for pentode mode (see below). 

The Manquest Tech article is pretty dry reading and a bit jumbled IMHO. It does clearly state things in a way to sell their products and why. Basically your coil looks to be a low leakage CMC but the cover will help with shielding...but again shooting in the dark because of conductor size/type and core type. In your BAC80 example you say that it is double the 3K load...but on the cutsheet page D2 under a "_distributed load grid tapping 43%_" it does show 6K in Push Pull and I am Assuming that is an XL value. @¿@ Have NO idea where or why they came up with the "_>=8H per kohm of R_plate measured at < 1/10,000 of rated output power_". Especially with the <1/10k rated output power. They must have some serious equipment to be able to measure this and or it may be some Physics/EE thing I forgot after 30 years. The site is definitely for Hi End audio file components though.

Honestly, I can't say if you missed something or not so All I can do at this point is sit back and  :Popcorn: 

I get it about the torch/mill size!

~PJ  :Popcorn:

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rendoman (Sep 23, 2016)

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## rendoman

Sorry, I thought I wrote in previous posts  :Roll Eyes (Sarcastic): 

El34, amplifier part, for now follows datasheet specification, then :

anode voltage 300, grid 2 300v, Rk 190ohm, Ia 80ma, Ig2 13ma, 11w power output with 8.2v g1 load 3,5k

I'm also thinking about second working point, for same output , with different load.
anode voltage 250, grid 2 250v, Rk 106ohm, Ia 100ma, Ig2 15ma, 11w power output with 8v g1 load 2k

https://frank.pocnet.net/sheets/129/e/EL34.pdf

Is nothing more than the official data. I will modify the circuit if necessary, but I think it's a good starting point.

Forgot frequency, numbers and formulas for now. I see that in similar amplifier circuit, when it's used an anode choke instead of an output transformer, values of inductance change for some reason between the 2 parts.

Compared to normal output transformer (3.5k load , 15H), inductance numeric value of an anode choke for the same load is maybe 50H or more. I tried to explain to myself with the formula of inductive reactance of coil, observing the products and the results I concluded that:

-For an "X" tube with "Y" internal resistence, anode choke inductance should be chosen 8 times the internal resistence 
putting in calculator 15k x 8 = 120H , and 20 hz frequency the result of reactance is 15kohm, same as internal res of tube. 
I deduced that for normal hi-end audio (range freq 20hz - 20khz typically) (8x is the "rule" in order to make a good anode choke for "X" tube.

-second step, reactance formula is valid at a certain frequency. I don't need 20hz in a tweeter, range will be 1-20khz for example.
It's important that the low-end frequency of my inductor (anode choke) should have a reactance equal to internal resistance of tube. 

My 3H coil for example, has a reactance of 15Kohm at 750hz. Taking the lowest frequency value for 15k, this coil should be good for an amplifier that sounds from 750hz to 20khz.

Using formula, I can keep 15k (I need this value fixed), I can also lower the frequency, at price of raising inductance of coil, then for example if I want my amplifier sounds from 100hz I will need 25H coil in order to have 15k reactance.

I think you're right about commercial sites, in particular this magnequest is pretty dry of info! I only tried to use this info to make a sense. Unfortunately even books have not satisfied my thirst for knowledge :Big Grin: 

One thing is sure! this post is pretty useful for my to keep record of all modifications done

I hope this page could be both of leisure and good reading even to the forum members :Smile:

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PJs (Sep 23, 2016)

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## rendoman

A good evening with a friend and some bourbon  :Smile: 

I'm going to put parts on frame, and trying to imagine a new plasma tweeter. Position of sockets is good, I'm thinking about powersupply transformers, switches and other parts. I think I will buy a single 500va toroid and put a couple of relays in order to cut high voltage and maybe filaments.

The 2 long hexagonal brass are only for picture, although I like them cut short.
Step by step this monster is on! I hope!  :Big Grin:

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PJs (Sep 27, 2016)

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## rendoman

new front panel, as usual solid brass polished, I've improved layout of ammeter and switches for better cables position.
Next step, circuit!

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PJs (Oct 5, 2016)

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## rendoman

HI all
... that's not a good evening, unfortunately! 
I've not seen that a crucial ceramic resistor broke its rheophore, leaving uncovered a part of the circuit. 

Results: melted a mundorf capacitor, the outside of another cap, and damaged a resistor in only 10 seconds. There are also good news, flame is pretty big with only 50ma, imperturbable to environment, with or without semi-faraday gage. Shielded frame seems pretty good.
Autofire is more rapid than in the past.
Base is good, now I have to re-start tuning

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PJs (Oct 11, 2016)

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## PJs

Sounds like good progress! But maybe a "Bit under wattage" on the wire wound...and also way too close to other components. One thing about ceramic wire wound resistors is were the lead comes out of the ceramic. To much flexing of the lead and or too hot soldering close to the ceramic weakens the wire at the joint and they will break. They also make ceramic wire wounds encased in an aluminum heat sink you can mount to the chassis or a bracket.

For the foil cap you might try to find a replacement Spraque/Cornell "Orange Drop" epoxy resin type and can get them down to 3-5% if necessary. Pull the 100uf electrolytic and toss it...the bleeder hole is likely damaged from the excessive heat.

~PJ  :Popcorn:

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## rendoman

Thanks for advice!

I did some calculation and attempts in order to understand better the trouble...
In summary:

-initial circuit run at 55v between gnd and cathode, with 220ohm cathode resistor are 250ma current, 3 times and something over normal operation. Not good, this working point destroyed first resistor

- I added a 2,7k resistor from power supply to g2 of el34, a little better situation, but Always too much current. 37.5v gnd-K, 170ma anode current. (normal working point "should" be 300v, 83ma with -15v Vg)

Components are new and show correct measure with multimeter.
There remains only the anode choke, maybe the tube doesn't appreciate so much. Maybe turns of copper are not enough, and inductance need to be really higher, like in commercial product. 
I got 2 way, for what I see:

- recalculate a coil with 100H of primary inductance. Lot of copper, this time I use lathe 
- Try a high power alu resistor as you said, maybe 50w or more, and throw to the air some 25w. This way allows me to raise B+ for this circuit to 500v.

...everyday a new problem  :Cool:

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PJs (Oct 12, 2016)

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## rendoman

New update

Second bad evening, due to circuit.

I was losing my head to look for the cause of the problem, last time I lost some capacitors and resistors. 
I found that one tube Langrex, "matched" quad, was faulty. In the same circuit, with the other 3 tube of the same lot everything is ok.
Bad tube runs at 35v of bias, +/- 160ma, current so high that powersupply suffered. 

A couple of number:

- Normal value: B+ 300v , 290v on g2, 16v between cathode and ground, with 220ohm are 73ma of current. Good working point 

- Bad tube: B+ 270v , 233v on g2 , 35v between cathode and ground, with 220 ohm are 159ma of current. This combo melt cathode resistor.

I modified also the anode choke, now 27H, and 273 ohm (+/- like a good output transformer) This thing has almost no influence on results, for now.

I'm writing a mail to Langrex, through ebay, in order to inform the seller about the problem.

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PJs (Oct 12, 2016)

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## PJs

> -initial circuit run at 55v between gnd and cathode, with 220ohm cathode resistor are 250ma current, 3 times and something over normal operation. Not good, this working point destroyed first resistor



Yup, a 5W resistor won't hold up to 13.75 watts very long...surprised nothing else went. Can't understand how a matched tube can be that different unless the cathode was shorted internally somehow¿ And the Bakelite base of that tube is singed! @!@ Hopefully your power supply is OK and they will send you a replacement?

I'm assuming this is the same "Cathode Follower" circuit you showed me before. That's not a typical setup for a CF...Might want to take a look at that as I suggested before. Think I sent some links on them way back in the thread...if not Google it.

~PJ  :Popcorn:

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rendoman (Oct 21, 2016)

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## rendoman

Yes sir! Circuit is similar, updated for different tubes, in order to have more or less the same power of oscillator part, a good old rule with old transmitter, as I read  :Smile: 

CF part is good as in the past,luckily something works! With 300v anode supply I get half voltage output to drive oscillator.
Not enough to bring the hell on earth, old good full flame with bright red plate near 200ma 1,1kv  :Lol: . 
Still enough to achive a big, not extreme flame with still grey plate. I will play with coils and working frequency, even if I think that actual freq is good. Although I must say that this circuit performs better with tubes really hot.

The most spectacular working point tried, unfortunately I got no pictures (and maybe I never wrote here, because it was crazy) , was 1,3kv with ammeter in heavy over range, up to 250ma, with the typical sound of pointer against block. Small flame and pesky bright white from anode... That's why tubes hate me  :Roll Eyes (Sarcastic): 

I hope ebay seller will reply Tomorrow, I think as you, some short circuit inside, or some strange grids structure, no signs on bakelite base, or visibile inside, the trouble should be inside.
I hope for a replacement, even if I bought a quad matched set ( I don't believe ), and I wonder how they can add a single tube with no matching reference.... I think I should close both eyes :Flame:

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PJs (Oct 12, 2016)

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## rendoman

Hi all!
I tried some circuit with fun tonight.
Because of many trouble with circuit, I wanted to test single el34 tube. I decided to make a fast amplifier on a relay socket, driven by old audio generator, capable of delivering 10v rms at 1khz, according to datasheet enough for undistorted output. El34 in triode now is good, but I have for the second time sockets-parts issues. Hope to find the cause soon

I will try in the coming days different bias and pentode mode, plus a better driver. Now tube is running at 52ma, with light warm cathode resistor, I'm on the right path

I also measured my ecc82 first stage, 35v rms output with less than 0,2v rms input, with a nice sine.

For the trouble with seller, he sent me a spare valve, which it is , more or less, a confirmation that there is no a real matching. 

  

Ecc82 driver, last picture with 227khz  :Big Grin:

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PJs (Oct 21, 2016)

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## PJs

Hi Stefano, I'm not sure what I'm seeing on the scope...assume channel 1 is the EL34 and channel 2 is the ECC82 signal outputs¿

Is this the spare tube? We both new they weren't matching these to any real spec...its a huge deal to go through all of a production run and matching tube curves plus aging times and precision setups. That is precisely why they Cost so much. This was just Advertising to suck you in. 

Those old 833's I had were matched by RCA and went for about $300 a pair back in the day!! These were on Ebay and don't even say matched pair Nor have gold Grids and definitely are Not RCA! But here is a real find on Ebay.

The sine waves look Very good at 1khz, spec voltages, but found it interesting that at 18khz channel 2 leads channel 1 and at 20khz it lags a bit? It appears that pushing the voltage on channel 2 is creating a phase shift...maybe slightly over driven. The good thing is even at 228KHz all you are getting is a ~90º phase shift and no distortion...that is impressive...be curious to see if it comes back to normal with a 35v on the ECC82.

You seem to be on a good path now, Congrats!

Until then, ~~ Keep your voltages nominal, your gain to 85-90% and your eye on the prize! Sparks _will_ fly.  :Stick Out Tongue: 
~PJ

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rendoman (Oct 22, 2016)

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## rendoman

Hi!
the tube is still traveling, Hope I will have in few days. You're right, pure advertising about matching, like many Others dealer. Next step on metal frame, I have buy belton, or anyway new high quality sockets, not chinese, something good, in order to have at least some more quality.
833a, love this tube!

Ch1 is Always linked to signal generator, ch2 on output of el34 in first set of pictures, and output of ecc82 in second one. You have a very good eye! I noticed that at 18khz output sine appears a bit translated, I will do a better thorough test to see correct levels at diferent sample rate. It curious too the 227khz test, I did for pure curiosity, but I did not expect this results  :Wink: 

Thanks for the advice! coming soon new tests! 

ps: this is the chinese datasheet of el34 tube. Ecc82 is a 6189w special quality, siemens

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PJs (Oct 24, 2016)

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## rendoman

Hi! 
Today I received the single spare el34 from Langrex, for free, it's a good seller for this.
I tried the faulty tube in new circuit, still gives bad results, I think I will test my new glock (arrival scheduled for this week) at shooting range with tube as target  :Lol: 

I made some experiments with ecc82, single ended, one or double triodes connected. Both circuit give good results, for a se amp with el34, a single unit should be fine. 

With 1v rms input (2.83v p-p), I got 13.7v rms or 38.8v p-p, enough to drive el34, maybe the right choice.

I tried el34 triode at 52 and 78ma, with same B+ but different cathode resistor. Unfortunately I can't find ceramic 8 ohm resistor as dummy load, I only see the anode amplitude for now. 52ma gives a better swing, and a colder rk, 78ma give imho too high temperature on 10w resistor and less amplitude. I will try soon with 8 ohm load and another output transformer

I tried also el34 in triode mode with good results, I think I will build an amplifier for my setup, this tube worth!



Ecc82 single ended, half triode


El34 triode, 19,5v bias, 375ohm cathode resistor 


El34 triode, 16v bias, 220ohm cathode resistor

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PJs (Oct 24, 2016)

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## PJs

Looking Good Stefano!  :Clapping:  Glad they comp'd the tube for you! 

The 16v/220 KR seems to lag just a skosh but the 19.5v/375 KR leads a bit more than a skosh...might try a 330 ohm at the 16v. That should put it at 0º...and the amplitude looks better at those lower values. It should be plenty of gain for your need but will depend how well you couple it and the quality of the oscillator/HF circuit.

Not sure what to say about the 8/10 ohm...more henry's might help???

Keep up the faith and the force will be with you! Great work!

~PJ  :Popcorn:

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rendoman (Oct 25, 2016)

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## rendoman

Hi all! 
Big update this time!

After a night, my plasma speaker is running!
Trouble as usual:* 2 new capacitor purchased from an Italian shop (the same of noval defective sockets).*

Few words about, I did a fast run, no hum, no noise, good and loud sound. The shielded frame works perfectly even if I soldered fast some components inside.

I have to try for my curiosity the range with microphone and software, 1khz is loud, maybe 2khz is the usable fq.*Finally I can tune the circuit, there is lot of work to do, tubes run in full safe operation mode now, I can squeeze more power from both*hf unit and modulator (remaining in datasheet range).

Next attempts:

- pentode mode amplifier unit
- raise driving voltage of oscillator at maximum (datasheet)
- try higher mhz working frequency, different coils and cap (flame is fully silent)

With my new modulator circuit flame runs from 10 to 20mm, from 50 to 110ma at 1kv.
No red plate, no red grids, power transformers run at low temperature.
Autofire is Always running, no strange behavior noticed.
In few words: circuit is stable and well running, now is labor limae!

For comfort I used semi-faraday gage, it works perfectly, see differences in pictures with neon, at the side is not possible to fire neon, even the rf emission on top is really reduced compared to full air coil.

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C-Bag (Dec 13, 2016),

PJs (Dec 9, 2016)

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## PJs

Been a bit anxious to know how you've been doing with this great project. Excellent news and progress Stefano! The Plasma Flame looks perfect and if it's quiet and tubes running as indicated, that is wonderful. Was that flame at 1KHz? Your makeshift cage also seems to be pretty effective. Are you still planning on running it horizontally into your horn? How are the ozone levels with this plasma size?

Small advice about raising the input voltage to max data sheet. Typically you would want to run it at about 80-90% to stay out of distortion range and not generating too many harmonics. A test at max is fine but running should be below.




> - try higher mhz working frequency, different coils and cap (flame is fully silent)



A little confused by this...is the flame not completely silent now? What frequency are you running at now? Not sure a few MHz will make that much difference for all that work.

Very happy for you and the progress you've made...a long way over a 18 pages and a years work!!

Till The next installment,  :Popcorn:  ~PJ

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C-Bag (Dec 13, 2016),

rendoman (Dec 9, 2016)

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## rendoman

Hi PJs!
Thanks! Yes both the pictures of flames are close to 1khz, I've seen that with full flame there is some more fuel to low frequency and a bit more volume (but not so much). Makeshift cage is made from 0,8mm steel, a scrap folded with no glory  :Big Grin:  , but really effective looking the neon result, I'm impressed! 
Imho ozone now is not so much, even at high flame, you can only smell a little with nose over flame, in normal room I don't think it is a problem.
I want to make quartz chamber as the initial idea, coupled with a 900-1000hz cutoff horn, that means +14-15db of spl, plus the full degradation of ozone. 

Max g2 imput of oscillator is 250v, now I'm running at 160v, near 65% , I'm not so sure about giving more volt, can be useful as study, but not for sound maybem you're right about distortion

Flame is completely silent and with a good shape,now freq is 12mhz, I want to try 25\30mhz, flame for sure will be shorter. I want to make this experiment to see what will happen to sound, honestly I think the actual frequency is good enough.
I'm thinking about position of flame, orizontal horn for sure, with vertical coil and a sort of ceramic connector for tungesten - copper wire, I have to found some good old isolator and Mount it over a teflon round bar.

I'm thinking for other options  :Roll Eyes (Sarcastic):

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C-Bag (Dec 13, 2016)

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## rendoman

Hi!
Something interesting today!
No tech or dissertations, only video and some feelings about plasma.

How does it sound? Sound is amazing! (not because I built it  :Big Grin:  )
Circuit is running as fullrange, with no input filter, not the best condition for music, but very good for test.

There is some clipping at full volume probably due to presence of bass, overdriving the el34 amp. 
Highs and mids are something different from normal diaphragm speaker. Sound pressure is high, with a good aluminum horn and a very good coupling I bet this circuit can face my sensitive fullrange system.

I'm at the beginning, circuit is running in safe mode, I have many things to try and to adjust.
I did a fast measurement with Rew in the room, just to know more or less how this thing works. I see a very good response from 4k up to 20k (sorry but I have poor microphone, it reaches only 20k) I hope with some ideas I have to gain 2k range. It's still impressive how much sound can produce at 1khz, considering size flame and driving.

The funny thing is that it took me so long to make running the circuit hot (do you remember red cherry plates?) , consuming lot of current, and now I got the same flame size with half clean current!

I post 3 videos, recorded with camera, not best quality but better than nothing  :Roll Eyes (Sarcastic): 

https://www.facebook.com/stefano.ran...1212254124884/

https://www.facebook.com/stefano.ran...1212406048682/

https://www.facebook.com/stefano.ran...1212316966455/

Ps: flame in orizontal is perfectly straight

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C-Bag (Dec 13, 2016),

PJs (Dec 13, 2016)

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## PJs

:Clapping:  :Thumbs Up:  Actually quite remarkable considering the simple protocols for these tests and you were streaming audio from a video probably in MP4 format. It doesn't surprise me the DB levels that you achieved, with good clean interfaces between stages at proper power levels. However I noticed these were run without running the Calibrations on your sound card, and ECM8000 mic they are likely skewed a bit. For me the Ears have it in the long run as to the _f_ response once you take a look at some detail in the RTA.

I can't remember if your frequency generator has a sweep function but that would be where I would be heading once I calibrated the sound card and mic. If it doesn't it might be available in your REW software and I would also run a 24 octave RTA test with the mic at 1 meter. Once you take it through those places I would probably use some solo classical piano to get a feel for what it can do in real life. The celtic was great to hear but violin strings have some interesting harmonics for this level of testing, imho.

Personally when I test speakers for my ears and a room I use a vinyl of 

 not only because it is beautiful (imho) but the pacing and individuality of the notes on her Steinway give you a clear indication of what the speaker/system can reproduce particularly the last bar or so.

If I may pontificate a bit more  :Embarrassed:  : Consider that you have built a wonderful analog tube amp with tenacity and verve that feeds an incredible plasma speaker you designed and Built!  :Hat Tip:  But when you feed it with an mp3 or 4, these are nothing more than an "Interpolated" version of an "AC" audio signal (an algorithm to simulate the sine wave). For MP3's anything above 192K begins to add artifacts and at 320k about 1/3 of the signal is artificial. I was shocked a few years ago when I developed a circuit that would decode a 19.2Khz (narrow BW ~±.2Khz) signal from an audio MP3, that I had to build a 4 stage modified Butterworth filter just to get it out of the "Interpolation". Beyond 192K sample it started to fail because of the artifacts introduced. Even adding stages didn't really help. The Scope doesn't lie and 24 octave RTA shows it on a grand scale. None of this changes the fact that it is a Digital age anymore but even AAC Lossless has some, and imho Wav/AIFF is the better way if possible if that is all you have to drive it musically...keeping in mind any conversions are just interpolations! Best of all, I recently heard that England is experiencing a rush back to vinyl (Yeah)! If you could drive this from a turntable I bet you would be surprised by what you hear!! Nuff Spew.  :Stick Out Tongue: 

Terrific Job Stefano, my hat is off to you....Congratulations Sir. On the downhill side now! 

Thanks for sharing. ~PJ  :Popcorn:

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C-Bag (Dec 17, 2016),

rendoman (Dec 13, 2016)

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## tonyfoale

As a newbie with just a few posts under my belt I was directed to this thread as an example of how things can take off on here. I read the first page and saw that there were 18 more so I skipped to the last one to see how things were going. I'll try and catch up with the rest later, but it is just to easy to spend too much time on the net reading interesting stuff, I like to make interesting stuff and finding time for both is always difficult. I work slower now than I did 55 years ago.
I notice that I have several things in common with some of the people here.

Stefano, I share your enthusiasm for motorcycles (you may find my web site and Facebook of interest). I live in Spain and suffer the same problems as you when it comes to buying what are regarded as industrial tools. The shops here don't sell to private people. Fortunately, I make 5 or 6 trips each year to the US, mostly to race but sometimes for work. When a trip is coming up I scour eBay and have stuff sent to a friend there. I have enough air miles to be allowed 2 free checked cases of 23kg each. If the trip is for a job then I fly business class and get a luggage allowance of 3 bags of 32kg each. So I usually come back loaded with hard to buy stuff here.

C-Bag (you must have a real name?), A mandolin player I see. that reminds me when I was between 8 and 11 ( I know that from where we lived at the time) my mother decided that there should be another musician in the family, she played the piano. My elder brother worked away from home and nobody ever expected much from my younger brother so I was nominated. The mandolin was chosen as my weapon. We lived in a country area of Australia then with no music teachers within a large distance so I was enrolled in correspondence lessons. The lack of a real teacher and my total lack of any musical talent eventually shone through and I was allowed off the hook.

PJs, I'm with you on the use of HSS tools for threading in non-hard materials. You can get a very keen edge which is difficult with inserts. I know that many people shy away as much as possible from screw cutting but really there is no need for fear. I am completely self taught as regards machining, in fact anything requiring manual skill, my education was theoretical, but being too ignorant to know that it was difficult I never had any trouble doing it. 

Although I got interested in electronics at 8 years old when first introduced to a crystal set, and later became a ham operator, I never did develop any interest in hi-fi and fancy speakers so I don't expect to be able to contribute much to this interesting thread.

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C-Bag (Dec 17, 2016),

Jon (Dec 17, 2016),

PJs (Dec 17, 2016),

rendoman (Dec 17, 2016),

Toolmaker51 (Dec 17, 2016)

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## C-Bag

Ok, now I'm officially intimidated  :Smile:  For the record my name is Tony too and when I went to register my usual net name was taken so I used a good pickin' buddy's call sign as it wasn't taken. 

I'm not sure folks who play classical, which was probably what your mother was wishing you'd play, would call what I play mandolin. I play mostly bluegrass and in bluegrass the violin is called a fiddle. Unfortunately they still call a mandolin a mandolin in classical and bluegrass. But like the difference between fiddle and violin, the approach is 180deg different. The joke is "How do you stop a bluegrass musician from playing?" .......put musical notation in front of him. When people ask what Bluegrass is a banjo picker said " 3 chords, a cloud of dust with sad stories sang through the nose in a upbeat way!" Nuf said.

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PJs (Dec 18, 2016)

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## PJs

Hi "Tony" Foale,
Just for the record I'm a novice to machining and mostly self taught, although I've been around shops all my life and careers. Thanks to HMT's and the great people here and Projects, I may be approaching the amateur level now. 

I got into electronics about 7-8 grade also. Galina radio to my first hand build O'scope in early teens, but had converted TV's to O'scopes earlier and worked summers for the local repair shop too, then to EE college...but never really used it as they were laying off EE PhD's when I got out. I was a tweener of tubes to transistor gen and started my education with the Radio Amateurs Handbook but never could pass the blinking key test for a first class license yet aced the rest of it. Stefano's Cone project peaked my interest and morphed through 19 pages now to this very difficult project of a plasma speaker which has always interested me all the way back to the 70's. Even though I haven't done tube stuff for at least 3 decades it's been great fun...And he has pulled it off other than some dial in, polish and pomp. Tenacity and verve is something I admire greatly!

I really enjoyed the article in the paper. Interesting it brought my trip in 01' to mind. I took a month long trip to Australia after an intense 3 year project and rode a RS1100 from Sydney to Melbourne down the coast. Just after leaving Sydney it started raining and by the time I got to Narooma I was a giant (6'6") drowned rat and stayed the night at a great pub. I thought about keeping the bike to finish my trip to Adelaide, then Coober Pedy...but did the train and bus instead, then 2 weeks in the outback camping and off to Cairns for some diving and sadly back to Sydney and one last Oysters on the Rocks with a pint and a fine cigar. Definitely a bucket list trip meeting great people and some golden adventures. I've ridden for 40+ years until an accident in 05' on my Sprint 1050ST. Been a family thing since childhood and dirt bikes. My Bro still rides HD's now. Always too big to race but ground 3 side cases off my 73' Z1 as a wanna be and got Gary Nixon and a few others to sign my Bell Hat. Also built a custom/blueprinted 68,69,70 Bonney with a trick Tiger Head from a pile of stuff I got from flat track racer I knew, way back when.

BTW, don't let C-Bag fool you, I know for a fact he has audio chops well beyond mine on top of his musical talents and mad shop prowess.

Based on seeing your DP sensors, flow bench and other projects, my hit is you can add to any conversations going on here. It's about sharing our ideas, thoughts, builds & Stuff with our peers and young guns freely here at HMT's IMHO. Jump in the water is great.

~PJ

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C-Bag (Dec 18, 2016)

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## Frank S

I've been lurking in this thread for months now. and like so many other threads it has morphed completely into something about as far from the original subject matter as possible which I have to say is probably why I visit it every time a new post has been made.
About as close as I can relate to any of the most recent postings in this thread would be C-bag's description of bluegrass.
I am one of those rare persons on this planet who just about never listens to any kind of music at least not for more than a few minutes at a time. to my ears it doesn't matter the type be it classical rock metal acid disco rap country, bluegrass or whatever by the time it reaches my ears it sounds like the screeching of fingernails on a chalkboard, but then again so does the voices of most groups of people I encounter unless I am looking directly at any single person. 
However this wasn't always the case as a young Teenager I used to look forward to the few random times when the famed Mr Earnest Tubb would come to our farm for a little pickin with my dad they having gone to school together as kids. I once met Him again at a USO show long after I had gone into the Army when he saw me sitting near the front row he stopped right in the middle of his song and singled me out.
Hey frank does your dad still make the best Hooch in Texas? When I told him that he had passed away. MR Tubb had me come up to the stage and do a duet with him as a tribute to my dad You have never heard a worst adlibed version of Waltz across Texas in your life but you should have seen the faces of 200 GI's when he calld me up

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PJs (Dec 18, 2016)

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## C-Bag

Good one Frank.

Ive been auditory all my life and music has always been a big part of it even though no immediate family played. Not until I took up guitar did my Okie G-pa and my Portuguese G-ma say they had both played mandolin when young. My great G-pa's it turned out were both musicians. But my parents on both sides only played the radio  :Smile:  I didn't start playing until I left home because everybody was such a critic. I'd been playing mandolin for a couple of years and we would always go out to breakfast with everybody on Saturdays and on the way home I'd always listen to friends who were dj's on KUOP the University of Stockton radio station. They would play all the many flavors of acoustic music all day long on Saturdays. As luck would have it, they played Rose and the Maddox Bro's big hit "Philidelphia Lawyer". After it got done I said to my then spouse " how did Rose ever get so famous with a voice like that!". I all but got hit, my X saying don't you dare talk about Rose Maddox that way! She was my grandparents favorite singer! You'd be lucky to play with somebody so famous! 

I said yeah right.....and as we pulled in to the car port I could hear the phone ringing. I ran in and it was our fiddle player and he was all excited because, yeah, you guessed it, Rose Maddox was playing the big concert on 4th July in the park and we were picked to back her up. Since her bro's died she would just have some local bluegrass band back her up. We never did get a chance to practice with her and our band would open and then back her up. We met her right before we were to open backstage. We had just gotten her best of albums and went over her songs. Since we had our instruments the guitar player said to Rose how about we do a song? She called something and we knew it. The guitar player who was classically trained started to play it in the key on the album and Rose said"hold on there son! I've been singin' in Reno for 3wks and we're going to have to drop er down a coupla frets!" So she would hum in Tony's ear(I was in a couple of bands where there was two of us Tony's) and he'd call the key, and she would have to do a vocal kick because she couldn't come in from a instrumental kick off. We did part of that song and I thought uh oh. Rose also felt no mercy for musicians who couldn't keep up and had fried the backup band the month before on the big stage at the big Grass Valley bluegrass festival in front 1,000's of fans. I tried not to think about it and the fiddler said to me as we went to do our set " what have I gotten us into.."

Our set went good and Rose came on to thundering applause. She right away stepped in front of our female bass player and once again hummed in Tony's ear, he called the key and she started singing and we came in. This went on for a couple of songs and Rose turned to me and said "what do you call your band?" I said we are Flatland String Band. She said, " a string band?" I said yes. Rose said " oh, you don't blow it, you pluck it".....the crowd roared and my face was so red I glowed. We went on like that with Rose strategically stepping in front of our pretty bass player every time she move out from behind her like she has eyes in the back of her head. Here Rose had been helped around and onto the stage by her niece, but after that first song the crowd just propelled her along and she was moving around like a kid. About a hour non stop in she called a song and it was a friend ours who was sitting in on banjo's favorite song(because of the banjo kick off on the album). He started in and Rose off mic said "hold on son" but Randy was in hog heaven and goin' for it. She tried again, hold on son and when she saw he wasn't hearing her got on the mic and screamed "STOP!" I swear the whole town of Modesto stopped and the first ten rows of seats had to pick themselves up off the row behind them! Poor Randy looked like he'd been shot. Rose just said, lady's first! And we went back at it. We did 90min and Rose said her thank you's and "for my last number I'd like to do a song in the key of love". We all just stood there while she grinned ear to ear...."the key of F!" And the crowd roared. I got to see first hand how a pro feeds off a crowd. 

Unfortunately a few days after we heard she'd had a heart attack and thought we'd go down in infamy as the last band she played with. She came back from it and sang for several years after. I've been blessed since to meet some of my biggest hero's who would probably be unknown to most, but some of the best mandolin players in the world and the nicest folks.

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PJs (Dec 18, 2016)

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## Frank S

So would I be correct in assuming that you are a 2 finger guy most bluegrass guys I've known played more 2 finger cords than anything else

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## C-Bag

Nope, I have always used all 4 fingers especially my pinky. I was into Joe Pass chord melody style jazz guitar before I got bit by mandolin. So it was natural to use all 4 fingers, what wasn't natrural was long linear stretches that the mandolin takes. All the bluegrass mandolin players I know use all 4 fingers because you can't do Monroe style rhythm chop chords with just two fingers as they would ring and like Mr Bill said "that ain't no part a nothin".  :Smile:

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## rendoman

Hi all!
I'm back!
I'm trying to do an experiment with old 813 tube.

Few words about, old circuit tuned for last plasma tweeter is completely out of focus, the circuit is running, but very bad. Flame is tiny, and the circuit draws few current, but it's normal. Volume is not so high, but the quality of sound at first listening is always impressive like my last prototype. A very good thing: There are no troubles about noise.

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## rendoman

Hi all
New update, I changed lot of parts of circuit, in order to have more efficiency, spl and distortion, I'm in the right way. 
Tweeter perform well from 300hz to 20khz now, lot of work to do to reach perfection!

I will build soon a coiler, I need to build special transformers for audio gear.
I also built a very nice electrostatic headphone

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PJs (Mar 9, 2018),

Seedtick (Mar 10, 2018)

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## PJs

:Clapping:  I applaud your tenacity with this project and glad you are still pursuing it!

PJ

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rendoman (Mar 9, 2018)

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## rendoman

Thank you PJ! 
That's a long project unluckily  :Frown: 
It's not like a normal amplifier, more or less a matter of a couple of resistor to achive the result, this plasma is really a beast.
I'm glad there are encouraging results, I'm a bit scared at the same time about the horn size for an ultimate version, 300hz tractrix horn is more or less half meter wide not possibile to made with my lathe, I'll have to make composite or cast... difficult choices!

That's the headset I built, electrostatic driver like japanese Stax units, sound result is Amazing

https://www.facebook.com/stefano.ran...4376382&type=3

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PJs (Mar 9, 2018)

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## PJs

Yep R&D takes time and some head scratching. Seems to me on the Horn you could size it for 1/4-1/2 wave and get reasonable results??

Nice job on the Electrostatics and saved yourself $4k. I about fell out of my chair laughing at the Squirrel video!!!  :ROFL:  Truly Hilarious and the goofy Dogs a hoot!!

Till Then, PJ  :Hat Tip:

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rendoman (Mar 9, 2018)

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## emikeo

Thanks rendoman. Learn lots of new thing from your post. Moreover, You are continuing this thread from last 3 years! Amazing! Some of this thread posts have useful information.

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rendoman (Jul 2, 2018)

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## rendoman

Thank you!
The plasma is still in development, even if I'm building an amplifier for my electrostatic headphone, I think I will close the plasma in the next winter , I hope!  :Cool:

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PJs (Jul 2, 2018)

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