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-   -   Where are the 833 amps? (http://www.diyaudio.com/forums/tubes-valves/24424-where-833-amps.html)

protos 18th December 2003 10:49 AM

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?

ThorstenL 18th December 2003 12:09 PM

Re: Where are the 833 amps?
 
Konnichiwa,

Quote:

Originally posted by protos
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.

Quote:

Originally posted by protos
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).

Quote:

Originally posted by protos
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.

Quote:

Originally posted by protos
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.

Sayonara

protos 18th December 2003 03:09 PM

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.

nickgreek 18th December 2003 03:33 PM

2 Attachment(s)
Class A2 SE 833 Stereo Amp
Protos, go to

http://www.geocities.com/bobdanielak/se833nynoise.gif

ThorstenL 18th December 2003 04:09 PM

Re: Re: Where are the 833 amps?
 
Konnichiwa,

You might want to have a look at this page:

http://www.jogis-roehrenbude.de/Lese.../805-Story.htm

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.

Sayonara

ThorstenL 19th December 2003 03:51 PM

2 Attachment(s)
Konnichiwa,

Quote:

Originally posted by protos
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.

Quote:

Originally posted by protos
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.

Quote:

Originally posted by protos
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.

Sayonara

dhaen 19th December 2003 06:01 PM

The essential problem with the 833 is the high Rp value.
You'll be in compromise between distortion and HF response (as all output transformers are, but worse).

ThorstenL 19th December 2003 07:46 PM

Konnichiwa,

Quote:

Originally posted by dhaen
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.

Sayonara

ReinoutdV 18th February 2004 08:52 PM

833 amp does work
 
2 Attachment(s)
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).

Reinout

NickC 18th February 2004 11:06 PM

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


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