unusual single ended triode amps

Discussion in 'Hi-Fi and General Audio' started by bottleneck, Oct 12, 2006.

  1. bottleneck

    bottleneck talks a load of rubbish

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    Thought I'd start a thread about single ended triode amps, and the relative merits of...

    1) the various pluses and minuses of different tubes when used 'single ended', and what results using these tube may have on the end result.

    2) THe availability of these less 'normal' tubes

    3) Some good old fashioned 'amp porn' of the more unusual SET amps, and any listeners comments.

    4) Builders comments - have you built a SET amp with something more unusual than a 300B?



    In a world of 'samey' subjects being talked about again and again, lets deliberately start off to talk about something different...
     
    bottleneck, Oct 12, 2006
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  2. bottleneck

    bottleneck talks a load of rubbish

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    to start off...

    what about the 2a3 tube when used single ended? why plump for a tube that (in a world of low power) gives just 3w per channel? What makes it special?

    Here's a cool internal pic of a 2a3 audionote kit amp, so you can see how theyre made.

    [​IMG]
     
    bottleneck, Oct 12, 2006
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  3. bottleneck

    bottleneck talks a load of rubbish

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    bottleneck, Oct 12, 2006
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  4. bottleneck

    felix part-time Horta

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    Cool.

    One of my upcoming DIY projects is a single-ended amp based on 807 tetrodes (strapped for triode operation), simply because I've never played with valve diy, and I already have just about everything I need - except o/put transformers - in the bits box. 807s are cheap, too.

    It should be good for maybe 10W, but mostly I'm hoping for something that sounds at least usable with the H2s.
     
    felix, Oct 12, 2006
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  5. bottleneck

    Anex Thermionic

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    2a3 isn't really an unusual tube its just that everyone is hung up on 300B for some reason.
    Here are some fairly interesting tubes housed in what are clearly the best looking chasis ever made :) :
    http://www.electronluv.com/html/amp/amp.php
    Some interesting circuits, certainly from a commercial POV.
     
    Anex, Oct 12, 2006
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  6. bottleneck

    Dev Moderator

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    Some very original looking and interesting designs there Anex.
     
    Dev, Oct 12, 2006
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  7. bottleneck

    murray johnson

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    9W from a single 2A3? at what level of distortion?

    The reason the 300B is popular is that you can get a reasonable amount of power from it ie 7-9 watts without having to resort to very high voltage HT supplies and the components they require. Also they don't require an output transformer with a very high primary impedance which then has a chance of decent bandwidth.

    Having said that many 300B SE amps sound poor (nice midrange shame about the rest) because people try to get too much power out of 1 valve by using OPT's with too low a primary impedance, an insufficiently sturdy driver stage, the filaments are powered poorly and the HT supplies are often weak. Still, they have the magic number 300B in them so people buy them.

    These limitations apply to most commercially made single ended amplifiers using DHT's. If attention is paid to these issues I think its possible to get good results from smaller tubes such as the 71, 45 and 10Y through the 2A3, PX4 and 300B type valves right up to the larger transmitter valves
     
    murray johnson, Oct 12, 2006
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  8. bottleneck

    bottleneck talks a load of rubbish

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    [​IMG]


    now thats what I'm talking about! ... I've seen them in show pics, but not for a long time...

    It's like someone thought ''what happens if I cross a valve amp with an expresso machine?''
     
    bottleneck, Oct 12, 2006
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  9. bottleneck

    hifi addict

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    I have always been put off SET amps and gone for push pull. But I did hear an SET using 833a valves producing over 100W. But at over 300K it should have sound nice.

    833a valves are becoming quite rare, there is I bevieve a manufacturer in the Ukrane still making them. I have asked a couple of people to try and find somne for a future project.
     
    hifi addict, Oct 12, 2006
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  10. bottleneck

    bottleneck talks a load of rubbish

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    Don't think I've seen 71, 45, 10y or PX4 SET amps in the flesh.. any good ones worth a pic?

    Let's have some more SET amp porn! :D
     
    bottleneck, Oct 12, 2006
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  11. bottleneck

    RobHolt Moderator

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    Martin, I ran the H2s from a Sonic T a few weeks ago - about 8 watts or so and it drove them to deafening levels without distortion. I think 10 clean tube watts is ample for the 2s.
     
    RobHolt, Oct 12, 2006
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  12. bottleneck

    bottleneck talks a load of rubbish

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    more from the electron luv site....

    I know this is a SET amp thread, but check out these speakers they do..... Western Electric, eat your heart out!!!

    [​IMG]
     
    bottleneck, Oct 12, 2006
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  13. bottleneck

    RobHolt Moderator

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    Now this is an amp.........

    [​IMG]
     
    RobHolt, Oct 12, 2006
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  14. bottleneck

    bottleneck talks a load of rubbish

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    wow, hehe.

    what can you tell us about it rob?
     
    bottleneck, Oct 12, 2006
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  15. bottleneck

    Paul L vinyl and valves mostly

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    Chris, using the description provided to me for future refernece at the time I bought my amps mine are:

    AI First Audio specs of directly heated triode (DHT), class A, no feedback, push pull, choke loaded all polypropyene power supply, solid silver wired, solid state Hexfred rectifiers for the HT supply, Schottky rectifiers for the DC heaters. Valves: 1 6922 or ECC88 driving a phase splitting transformer through solid silver wire to 2 6B4Gs. Thse are monoblocks at about 7.5W each so each tube is running at about 4W.

    The preamp (unbranded) is single-ended choke input followed with a Black Gate capacitor then choke loaded to another Black Gate capacitor to a pair of 12B4 valves in an Anode Follower configuration, valve rectified EZ 81 power supply, Alps Black volume control. Schottky rectifier DC heating, zero feedback design.

    Personally, I don't understand a word of it.

    Alas, unless there's a word or two in here that gets some kudos as I'm not running SETs I guess I can't play. At least I can carry on listening though!
     
    Paul L, Oct 12, 2006
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  16. bottleneck

    vibbles

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    not really porn but here's my 2A3 Loftin White


    [​IMG]
     
    vibbles, Oct 12, 2006
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  17. bottleneck

    RobHolt Moderator

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    IIRC it belongs to Paul Barker, is dual mono, uses four tube rectifiers, has interstage transformers and 211s on the output running at over a kilovolt.

    Switch on and RUN! :redrum:
     
    RobHolt, Oct 12, 2006
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  18. bottleneck

    bottleneck talks a load of rubbish

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    hi vibbles, how do you find it compares to your glasshouse 300b set?

    (by the way I had a couple of hundred quid in upgraded bits, and it sings now)

    I've got the details somewhere of what Nick upgraded for me, if you haven't already cool-ified yours :)
     
    bottleneck, Oct 12, 2006
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  19. bottleneck

    Dik Dolan

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    I'd be interested in your upgrade list, bottleneck. Mine is still all bog standard, and my soldering iron is getting twitchy.....
     
    Dik Dolan, Oct 12, 2006
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  20. bottleneck

    felix part-time Horta

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    I'm sure it would be! Perhaps instead of 'useable' I should have written 'worth listening to' ;)

    Still haven't progressed things very far, but since power output isn't a priority, I would happily trade off for better performance such as Murray highlighted in his post. Lots more reading to do first, though...
     
    felix, Oct 12, 2006
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