• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Where are the 833 amps?

I have been thinking of trying my hand at a good tube se amp.I have only done solid state up to now.However I am a little bit put off by the low power of sets and recently I noticed that the WAVAC 833 is accepted as one of the best se amps around and it can do 150w .Even Rosenberg raved about this amp.
So my question-being a tube newbie-is why are not more people using these tubes if they can sound so good and solve the power problem.I have seen only very scant info on DIY amps using this tube.Is there some kind of prejudice because it is a RF tube?Can it sound good with the proper circuit and components?

protos said:
I have been thinking of trying my hand at a good tube se amp.I have only done solid state up to now.However I am a little bit put off by the low power of sets

Why? Practically all Low Distortion and Low Compression Speakers have a sensitivity well sufficient for use with a 300B SE Amp. So why would you NEED more power.

protos said:
and recently I noticed that the WAVAC 833 is accepted as one of the best se amps around and it can do 150w.

It may do 150W, but neither of two 833 SE Amp's I heard (Metropolis and Wavac) sounded especially good. Yes, they deliver a lot of power, but using a suitably good speaker I(Koechel Horns) I found the Wavac EC300B infinitly superior to the 833. Now if the speakers had been the usual inefficient socalled "High Fidelity" speakers abounding no doubt the EC300B would have run out of steam, but as it stands I think it is by far the best of the Wavac Amp's I heard (all else being equal) but is again eclipsed by the AN JP Baransu (all silver single 300B SE).

protos said:
So my question-being a tube newbie-is why are not more people using these tubes if they can sound so good and solve the power problem.

Well, there is of coure no power problem, just a "bad speaker" problem and secondly, while not bad the 833 does not seem to sound all that great. Lastly, getting the kind of (output) transformers that are required to operate the 833 is no minor problem (try making a good 10W RMS @ 20Hz SE Transformer, then you know how much fun it is to make one for 150W @ 20Hz) and the extermely high voltages needed to operate the Valve in Class A1 make the powersupply (and electrical safety) a major hassle, if you go class A2 as with Wavac there are many othe problems.

protos said:
Can it sound good with the proper circuit and components?

Any Valve can do so, given exactly the conditions you mention. However, a few ones (like the 10Y and 45) can sound spectacular, something which most valves do not manage.

My recommendation for a High Power Amp would be to go hybrid, circlotron maybe using suitable PNP devices combined with a Valve device (2A3 or such ?) as CFP. Such a thing is highly scalable and can be made to deliver almost any power output you like.

The reviews on the WAVAC were very good but anyway what about using the 6c33 or 845.I understand you could get about 20w out of them which would probably suit my purposes.Or is the 300b a one way street to get the best sound without resorting to huge horns.


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Re: Re: Where are the 833 amps?


You might want to have a look at this page:


While in German it does show the way Ronald arrived at something close to the Wavac 805 Amp (around 40 - 50W, more than enough for most speakers). All transformers are Tango and not cheap at all (think around $ 600+ for the Outputs and Interstage Transformers) and the truckload of BG Cap's and the like are also not cheap.


protos said:
The reviews on the WAVAC were very good

Yet few if any where made under conditions where the Speakers where not drastically compromised (meaning the usual High End dreck). Gizmo raved about all Wavac Amp's, but he was a very enthusiastic gentleman anyway.

Don't get me wrong, the Wavac and Metropolis 833 Amp's both sound perfectly fine, but they lack what makes certain amplifiers more than "fine". If you must have 100...150W and if you must have the "buzzword" SE DHT - then the Wavac or Metropolis (or suitable DIY) are your choice, but I feel that given the total effort a revision of the whole system may give better results for less investment.

protos said:
but anyway what about using the 6c33 or 845.

I have not heard many 6S33 Amp's and non in SE, but it seems an interesting Valve, especially as the low anodeload should make getting really good transformers made quite easy. It is not DHT and not as linear as the 300B but can offer a bit more power and may be easier to get work well enough.

I think the attached circuit would be a good starting point. You may have to get the Output Transformer from somewhere else, Iso/Tango may not have any.

I'd also try the 6072A instead of ECC83 with 2K cathode resistors and 5687 instead of 12BH7 and loose the loop feedback. Try a 1k resistor in the cathode (before the RC combo) to lower the gain of the second stage. This then is close to the famed "Ongaku" and I know this driver to sound well. Use a Nippon Chemi Con VX series cap in the cathode of the second stage and a Silver Mica coupling Cap. Using a 0.047uF Cap (readily available) and a 510k Gridresistor for the follower (270K on schema) and you will be fine.

Use generic Nichicon VX series Cap's for the various PSU decoupling Cap's and better quality "Computer Grade" Cap's for the rest of the supply, you want "Big Can" types, though I have good stuff about Panasonic TSHA Cap's, so maybe worthwhile trying these in the main PSU.

I'd avoid the 845 because of the very high voltages, which pushes cost up and because of their somewhat slow and opaque sound (from all the 845 Amp's I have heard). Better use the 211 but becareful, 211's can sound quite steely. If using the 211 build a "Pseudo Ongaku", e-mail me directly for some comments on this kind of thing.

protos said:
Or is the 300b a one way street to get the best sound without resorting to huge horns.

In my view, using current production output valves and medium sensitivity speakers - yes. The 300B gives enough power for most speakers with a genuine 93db/W/m+ sensitivity Speakers. Using 2A3 or 45 requires you to push up the sensitivity and thus size. There are other good sounding valves with similar or more power output (like someof the old Klangfim stuff) but not much in easy current production and thus a dicey proposition and again, cost spirals.

For starters I'd recommend building a 6S33 SE Amp as noted above, maybe Parafeed, meaning you can use fairly easy to get Anode Load chokes (I think 10H/200mA PSU Choke from Hammond - 193J would work for a starting point) and a 115V+115V : 12V+12V 100VA Torroidal Transformer as output and a decent 47uF/600V MKP Cap (bypassed) as Parafeed capacitor, that is quite cost effective.



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dhaen said:
The essential problem with the 833 is the high Rp value.

Not in class A2 with Cathode Feedback a'la Shishido/Wavac, that is where the genious of the late Shishido san comes in. Of course, no "Zero Feedback, Class A1" which explains the slightly weired sound of the 833 Amp from Wavac, but not of the Metropolis one, which A1, High Load Z, zero feedback.

833 amp does work

Just finished my 833-amp. After a serious breaking-in and listening time i am pretty pleased with the result (personal opinion of course). Trying to describe the sound is not easy, but "effortless" is a nice start.
Funny: a huge tube, a massive power supply, half a truckload of components.......and the sound is ...."light" "airy". Don't get me wrong, there is seriious grunt.

The amp is in two monoblocks with their own powersupply. And yes: you need a substantial amount of transformers. I'm using 135 kg of transformers and of course that explains why not a lot of people are going for the nice tube.
Pricewise it is a nice tube as well. NOS is still available and new is nowadays produced (even a new carbon based anode).

The amp is in A2 and currently i've set the B+ at 1000 V. In the future i can switch to higher voltages in trying to find the sweetspot.

I'll attach a picture of the amp, remember there is another unit just as large which is the power supply.

Lots of luck with building and please be carefull with the high voltages (the other reason why there are not as many 833-builders around).



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Nice amp. Will build one after my current project.

Where did you get your output trans for this amp?

Could you describe the configuration of the amp. How is the gain stage configure and driver configuration and finally the 833 stage.

How did you hold the tube upwards in that direction. Some mounting brackets under the hoods. I see you have a fillament socket for the 833a. Are those easily available.

Thanks for the help
833 amp continue

Hi Nick,

you had some questions:

- transformers: allmost all my transformers (power and signal) are made by Heart. Nice stuff. Maybe i'm lucky to live in the Netherlands where there are 3 well respected transformer-"sources" are (Heart, Tribute and AE).

- schemtatic in words: input transformer - 6SN7 - interstage - 300B - interstage - 833 - output transformer. No feedback.

- one of the more difficult things during the building of the amps was sourcing original tube sockets. Some well respected firms made them (RCA, ITT, Johnson) and i managed to get hold of NIB Johnson 124-212's. Most of the 833-sockets are fixed, but the Johnson's can swivel so it was possible to fix the tube socket horizontally but the tube itself vertically. The sockets themselfes are sturdy enough to "hold" the 833.

Now with a picture of the power supply attached. There are 2 umbillical cords from the powersupply to the amp itself:
- one with all the needed filament/bias/B+ for the 6SN7 and 300B;
- one with the 833 needed juice;

Hope this answers your questions ?



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High power on the cheap

For what it's worth i recently heard a cheap chinese Meixing amp where a 300B drives an 805. No idea about circuit details but the sound through a pair of chinese 'red rose' speakers (86db?) was awesome in dynamics, power and soundstage.

If i were to attempt building a similar amp i would probably start by buying a pair of the Meixing monoblocks - any diy effort of similar quality will cost much more than the asking (in China) price.
I was also looking at that model and thinking if the sound quality is up to par.At 900USD it is an absolute steal (Hong Kong) even with shipping it should work out very cheap.
So you say you liked it?Did you compare other amps?
I am seriously thinking of getting one at these prices and of course there are many possibilities of modifications.
But of course there are reservations because it is not a well known brand and I haven't seen any reviews.I wonder if the transformers are good quality as well.
I am building a boatanchor amp too.

Will have 5 chokes per channel,
7 mains trans(1.5Kva,200va,80va,50va,10va,200va,160va) per channel
1 output trans per channel.

Just the trans and chokes around 40-50kg maybe more

Will be attempting a stinct in weight lifting if i can carry this much.:)

Mains trans are cheap to custom wind them. However Opt are hard to be found in my country. They have the core, but do not have the technical skills to do it. Whats your impedance rating of your opt like impedance and current draw? How much where can i ask?

diyAudio Senior Member
Joined 2002

Does Heart have a web presence?

Under construction....

But you could visit the other ones by Rik Stoet:



FWIW, when Rik S. started in the early Nineties he had his iron wound in China for his kit amps. No idea if this is still the case though.


P.S. Just spotten this on the second site under "Aanbiedingen" and fell from my chair:

Quad II buizen mono blokken Euro 2.195,00
I was also looking at that model and thinking if the sound quality is up to par.At 900USD it is an absolute steal (Hong Kong) even with shipping it should work out very cheap.


From what i remember the price for two monoblocks was around usd1600 from the dealers i visited. You are presumably refering to the Catylink pricing - they seem to be high on everyone's hate-list in the area :)

I didn't compare to anything - all the dealer had were unknown to me Chinese brands. Don't think i wasn't prejudiced, previous limited experience with Chinese iron was less inspiring. As for the 3008A Meixing, i couldn't detect any bandwidth limiting on the bookshelf-sized rose buds. The mids were obviously coloured, presumably due to the speakers and the peaks had a bit of distortion (volume was set too high) but the huge images and startling dynamics were really impressive. And so were the quiet passages.