833a SET Amplifier Complete build

Final version of the 833a SET audio amplifier. Sounds pretty good...

[@alanm.thornton4055]

Man, I really wish I had the intellect and skill to design and build something like these!

[@boxingday11]

Very impressive, thanks for sharing your skills with us, best regards,carl.

[@BDBee81]

Immaculate!!! Congratulations on your final build mate, job well done. Second to none jd. All I need now is to ask you the inevitable,,,, that's right, EVERYTHING!!!!.. Hahaaa!! Although I do realise you deserve a well earned break away, from all things "glass & small" for as long as you need. Having also planned building by hand assembly a set of beasties like yours on my todo's list, stumbling upon your channel has thrust apon me a sudden shock wave burst of inspirational motivation. Thank you. That being said, I would only ever attempt to build something so meticulously in order and only with the advice and guidance of someone like yourself.. When I finish hand re-wiring a couple old EAB 202 output transformers and complete my current restoration I'll start sourcing bits and pieces for the "BIG ONE!!"... Unbelievable... Enjoy listeng to some more ear candy on your break.. It appears I'm having one of those big boys "Valve Moments" so it seems. Kind regards BrenDon.

[@thewtf]

Thanks for that! If I was doing it again I’d probably do without the smps’s as they do seem to produce some high frequency hum which only younger people can hear.Other than that it seems to work quite well

[@thevintageaudiolife]

Thank you for sharing, very nice build.

[@RWBHere]

Very nicely done! Thank-you for demonstrating it. All the best for 2020.

[@eugenepohjola258]

Howdy. That's not a tube amplifier. That is the Warp Drive from my Starship that got stolen ... Anyways. I would recommend using wires with the insulation rated to withstand the high voltages. In high regards.

[@drbarney1000]

I put my chokes on the negative side of my 1kV power supplies for my 833A plate and polypropylene capacitors rated at 2300 Volts and I don't have to worry about the chokes holding 1000 Volts. The Hammond 5 Henry chokes are pot tested only to 800 Volts so this is a good safety precaution. I also use Hammond 1642SE transformers and I am convinced there is no better transformer for the 833A, even on the WAVAC 833A which costs $350,000 and I think you get the inferior electrolytic power supply capacitors. You are better off building your own and you can build it better; no need to covet or rationalize "If I were a financial colossus I would want to buy a WAVAC 833A" which I am confident is not as good as what you can build.

[@nathan7265]

Can I have some links on your best build approaches and parts? I can give you my email.

[@drbarney1000]

@@nathan7265 Send me an email address and I have some lists and schematics for you. My 10 Volt 10 Amp power supply is a little crude because it used a 4.5 Farad final filter capacitor instead of active Voltage regulation.

[@sc0or]

Wouldn't it be better to feed an input tube first, and then continue with the others? I mean a filament current.

[@chrispza]

What a magnificent array of glowing toobs! Your power bill must have jumped since you constructed this. Since you have all this voltage to hand, how about directly driving a pair of electrostatics?

[@user-vh1xl7hh3t]

wonderful!! whos the Guitar player? Sound like Chet Atkins!

[@georgejobin1744]

WOW I am very impressed what a great job one of the best builds I have ever seen is there a schematic thanks

[@drbarney1000]

I don't know how to give you a schematic on youtube reply but email me at [e-mail].

[@MotorMouthMaul]

I would very much like to have the schematics for this.

[@ElPasoTubeAmps]

Very nice build. You and I seem to have a good bit in common because I use in one of my amplifiers, 866A and diodes for a bridge. I thought I was the only one that would do something like that. I also use a pair of 866A in a voltage doubler in my 833A RF amplifier. Not supposed to work MV rectifiers into a capacitor but it works for me. Lastly, I use 872A MV rectifiers in my AM transmitter. Love those MV rectifiers blue color... With your 1000V transformer into the bridge, I assume you get about 1300 volts on the plate and I see you have a 800 ohm bias resistor. Do you recall the bias voltage or cathode current? I attempted an AF amplifier with the 833A sometime back but only had push pull OPT and the core saturated quickly, right at about 150 mA, the quiescent current, so my LF response was poor. I do have a very successful 833A RF amplifier I run on 20M. TGTP and neutralized. Absolutely love it. Delivers 1KW to the antenna with ease and only 30 watts drive. I posted some videos of my 833A amplifiers both AF and RF but none of my videos actually are accurate anymore. I started my RF amp with a 50 ohm resistor on the grid, patterned after an ARRL article and it was terrible. 100 watts drive for less than 400 watts output. The medium mu triode like the 833A can not be run GG so finally I accepted that and tuned the grid and neutralized it to get the gain and performance I mentioned. Very nice to see you were so successful with your amplifier build. I started a SVT-572-10 amplifier a few months back but got distracted and need to get back on it. I use a simple RC coupled 6SN7 driving a 5881 to drive the triodes (1000 volts on the plates) but I am not satisfied yet with the performance. I am considering that maybe I need to put a load on the plate of the 5881 at around 1250 ohms - something it would see across a 5K plate to plate push pull transformer. Any thoughts on that? If I understand your video correctly, you use a 1:1 driver transformer to drive your 833. I prefer not to use driver transformers if I don't have to and from studying many Collins and Gates commercial transmitters, I see they do not use driver transformers to drive push pull 4-400A in class AB1 modulators. In my experience, I have not found it necessary to run DC on the filaments. Maybe I have just been lucky so far. Again, very nice work and thanks for taking the time to post. 73 WA4QGA El Paso, TX

[@thewtf]

Thanks for the comments David, yes I have seen some of your videos; some excellent work going on there in El Paso!! Yeah, I starting using hybrid MV and solid state bridge rectifiers a while back and they seem to work fine. Got that set up in my GU81m amp in the screen supply and also in the 833a amp.Yes, the plate voltage on the 833a's is about 1200v but they work at zero bias. The 6B4G triode driving iy has about 750-800 ohm cathode resistor which is pretty standard. Like you I have since tweeked the amp since the video was posted...I was using a switch mode PSU for the DC supply of the 833a's heaters but found that it was introducing noise about 20 kHz so have replaced it with a conventional DC supply. Also reduced the NFB a bit and now it sounds better than ever. I don't have much in the way of all that fancy audio testing gear like you so I'm a bit limited in getting accurate data on my amp performance ....it's a case of it sounds OK must be right !!! All FB on the 833a RF amp... if you look at my video on the 3-500z amp, well that started out as two GU48's (equivalent to 833a's) in parallel but I just could not get it to work. Big triodes are a nightmare to get working properly.Not had much experience with the SVT-572-10, but I did build a modulator with a pair of 811 triodes driven by a pair of 807's via an interstage transformer which worked pretty well; maybe something like that might work with your 5881's. 73's from the UK, Justin GW0FZY PS: look me up on QRZ if you want to e-mail about anything

[@DScottDuncan]

Nice work! So Class A operation, right? Would be interesting to bench test it and see the THD and power you are making. I'm sure it sounds great. I like valve equipment and used to repair televisions, receivers and build ham radios from Heathkit back in the 70s. Thanks for sharing.

[@thewtf]

If I had some audio analysing gear it would be great to see what the THD and power out is. It sounds OK but I’m not an audiophile by any means!!

[@MM0IMC]

The lights out portion of the video would make an excellent QSL card background. Do the mercury rectifiers give out a lot of UV?

[@justinwoolgar9853]

I believe they do emit UV but probably not a huge amount...the glass envelope will absorb some of it to a degree

[@MM0IMC]

@@justinwoolgar9853 I think some of the large, more industrial type ones would be of more concern. ;)

[@mrlam7003]

Would you please provide this power amp schematic ?

[@egbertgroot2737]

I looked at your website ... i am impressed! Any time left to sleep? ;-)

[@linefriis5774]

Very cool. :)

[@douro20]

It wasn't too long ago that these tubes were plentiful and cheap.

[@marcelwinkelhofer]

From where do you have these nice anode caps?

[@thewtf]

I think they came from eBay

[@adamjegas]

Can you send me the circuit diagram of the 833a power amp?

[@thewtf]

I’ll try and put it up on my website when I get a moment. Jetpropulsion.co.uk

[@adamjegas]

@@thewtf ok thank you^^ i will wait and i sent email about it

[@drbarney1000]

email me at [e-mail] so I can send you my schematics which are very much like the 833A stereo done here.