Supratek 845 PP crazy big 14 tube stereo amp anybody?

Discussion in 'Audio Hardware' started by Marsman, Mar 29, 2019.

  1. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
    [​IMG] https://photos.app.goo.gl/DqhGSk9vXHrKGE71A[​IMG]

    Here is a picture of the amp .. anybody familiar with Supratek amps. I am told this is a a 40 watt pure class A push pull stereo amp .. one of a kind i guess .. any thoughts / ideas to value etc etc I have a opportunity to purchase

    Just figured I would toss it out there

    Thank you
     
  2. Subagent

    Subagent Forum Resident

    Location:
    Arlington, VA
    The website indicates that custom builds are possible, and that products include a "lifelong warranty (excl freight) that is transferable." So, it might be worth inquiring with the builder for details and specifics on that piece.
     
  3. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
    I did he has little info on the amp anymore lol he has not been a ton of help but even then shipping to Australia is out of the question cost wise .. I even said to him that a amp that is a 14 tube 40 watt pure class A must have cost $8000 20 years ago and his reply was "yeah maybe but i always sold stuff too cheap" he also claims with the power transformers used it might cost as much as 20k to build today? I dunno I am not as familiar with tube amps as I am a solid state Mac owner
     
  4. Roger Beltmann

    Roger Beltmann Well-Known Member

    Location:
    helenville, wi.
    Pure class A or push/pull ? Can't be both
     
    SandAndGlass likes this.
  5. vinylkid58

    vinylkid58 Forum Resident

    Location:
    Victoria, B.C.
    Why not?

    jeff
     
  6. Roger Beltmann

    Roger Beltmann Well-Known Member

    Location:
    helenville, wi.
    Class A draws current for 360 degrees per tube. Class AB1 only draws current for a little over 180 degrees per tube. That's why push/ pull can give almost twice as much power. Each tube only does one half a cycle so it can be driven twice as hard. Basic electronics.
     
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  7. SandAndGlass

    SandAndGlass Twilight Forum Resident

    That amp is a class A/B if it is a push-pull amp. Which it appears to be.

    All class A/B amps have two output tubes per-channel.

    Most class "A" amps have one output tube per-channel, although some have two tubes that are run in parallel.

    Class A/B amps can also run output tubes in parallel. My Rogue M-150 monoblocks has a quad of KT88 power tubes in each amp.

    Class "A" is not push-pull.
     
  8. vinylkid58

    vinylkid58 Forum Resident

    Location:
    Victoria, B.C.
    Yeah I know basic electronics. You guys make it sound like class "A" push-pull isn't possible, and I'm saying it is. There are lots of examples.

    jeff
     
  9. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
    from the builder Mike Maloney (mick)

    "It would be Class A Triode Push Pull. It was a very good design, very good transformers. I'd guess around 40 watts clean"
    "Yes it was custom built, cant remember price sorry. Only one made,they were too costly to make more, there’s a web archive somewhere on a harddrive, I’ll see if I can find it."

    [​IMG]
    "It was a good amp, beast of a thing really.
    something comparable would cost $20k, but audio is in serious decline now.
    Is it working ok?"

    This thing is such a mystery lol
     
  10. Bill Hart

    Bill Hart Forum Resident

    Location:
    Austin
    There was a lot of love for his preamps back in the oo's--I think he stopped production but now is back. You can research some of the threads on Audiogon. Don't know anything about his amps--the main issue with one man companies is support and whether they stay in business- I speak as someone who owns quite a bit of equipment that comes from such small operations.
     
  11. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I'm with you on this point.

    Maybe you can share the "lots of examples" with your fellow forum member's?

    Speaking for myself, I'm not familiar with any and would welcome someone to explain to me how a push pull tube amp is also a class "A" amp.
     
    bluemooze likes this.
  12. Roger Beltmann

    Roger Beltmann Well-Known Member

    Location:
    helenville, wi.
    I heard they're bringing back the twilight zone.
     
  13. Subagent

    Subagent Forum Resident

    Location:
    Arlington, VA
    I know almost nothing about electronics, but the Audio Note website describes both the push pull OTO and Soro as "pure class A." And I am definitely not confusing them with the single ended versions (that based on my reading skills rather than any electronics knowledge, I hasten to add).

    The Audio Note (UK) SORO Integrated Amplifier is a Pure Class A, producing an outstanding level of performanc

    The SORO is available in a Push-Pull or Single Ended valve design.

    Push Pull

    It has been specifically engineered for sonic performance rather than technical specification, and fulfils all Audio Note (UK) Level 1 criteria: -

    Pure Class A Push-Pull Pentode operation

     
    SandAndGlass likes this.
  14. I must go and visit Mick. He lives in Margaret River also.
     
  15. vinylkid58

    vinylkid58 Forum Resident

    Location:
    Victoria, B.C.
  16. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Interesting.

    But as I look at this more closely, I see;

    It is one or the other, single ended class "A" OR class A/B push pull.

    In doing a google search, check out the search engine results page for "Audio Note (UK) SORO Integrated Amplifier".

    Check out the first two search results.

    The first one is for "Soro SE - Audio Note" and the second one is for "Soro PP - Audio Note".

    The SE is the single ended model, which is class "A" and the PP is the push-pull model, which is class A/B.

    Neither of the search engine results goes to a AN product page. The product may not be currently in production.

    Not being familiar with AN products (I have an EL84 based class A/B AN Kit amp), our member, @Richard Austen comes to mind. I thought we might ask him to weigh in on this issue.

    Then I happened to notice a product review on the Audio Note OTO SE Integrated Amplifier With Phono. As it happens, this review is from Dagogo back in 2008. It was reviewed by Richard Austen.

    Maybe he will be so kind to join us in our discussion and perhaps clear up some of this.

    Looking over the review, I see that it is a SEP design, which means Single Ended Pentode, as opposed to the usual SET, Single Ended Triode design. Both are pure class "A".

    This is my Decware Mini Torii, which is a 3.9-Watt, dual mono, pure class "A" SEP. The power tubes are 6V6GT's. There are two of them. They are the two tubes located to either side of the two large rectifier tubes in the center.

    [​IMG]

    I might add, that this is my favorite sounding amplifier.

    Class "A" amplifier's are single ended design's, where there is a single output tube per channel handing both the top and the bottom of the sine wave.

    A class A/B amp has two output tubes per channel, one tube handles the top portion of the sine wave and one tube handles the bottom portion, in a push pull orientation.

    A tube amplifier by design may be either one type or another. Some amps will run their power tubes in parallel, for more power. In this even, either design may have double the output tubes per channel. This is done to increase the total output power of the amplifier.

    The line,

    may be a misprint or something that I am not familiar with.

    Again, perhaps Richard might be able to enlighten us on this issue.
     
  17. Larry I

    Larry I Forum Resident

    Location:
    Washington, D.C.
    The issue of whether there is such a thing as Class A push-pull sort of comes down to definitions. In some books, if the tube is not cut off entirely, it meets the definition of Class A. To me, in the spirit of what is meant by Class A vs. A/B, a pushpull amp really is behaving as Class A/B. But, frankly, I don't think it really matters and the terms are meaningless--there is no meaningful distinction between a pushpull amp described as Class A and one described as Class A/B (it could be the same amp being described by two different people).
     
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  18. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I would say that the "treasure hunt" is still on.

    "The Quad II clasic has been recreated accurately with output valves and input valves the equivalent of those used in the original. The output valves produce around 15W per channel operating in Class A, which allow a gloriously sweet and refined sound with appropriately matched contemporary loudspeakers."

    Let's check out the specifications, shall we?

    [​IMG]

    You will note that there is a single GZ34 tube, which is a rectifier. Two EF86 tubes, which are the equivalent of the American 12AX7, which is a small signal tube. Finally, there are TWO KT66 power tubes. That would allow for a single KT66 tube running single ended in class "A".

    This is not a push-pull class A/B amplifier.

    The other amplifier's featured further down this page, are push-pull, class A/B amplifier's, having two output tubes per-channel.

    "With KT-66 output valves on the Classic Integrated / II Classic and KT-88 on the II-forty / II-eighty, the push-pull configuration is visually stunning, even when safely secured within the cage that protects them. The output characteristic is a superbly refined sound, matched with both classic and contemporary loudspeakers."
     
  19. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
  20. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Conventional naming, class "A" is single ended and class A/B is push pull.

    Of course "a pushpull amp really is behaving as Class A/B".

    I don't see the logic or reason for a push-pull amplifier to be described as class "A", because as most people understand that it is not.
     
  21. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I guess that I am missing something, but I don't see where this circuit is class "A"?
     
  22. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
    From the link .. I do not claim to know enought to debate
    The construction of the class A power amplifier circuit in push-pull configuration is shown as in the figure below. This arrangement mainly reduces the harmonic distortion introduced by the non-linearity of the transfer characteristics of a single transistor amplifier.
     
  23. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Good to know.
     
  24. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    That statement is incorrect. Push Pull can indeed be Class A. Both output tubes simply need to be biased to swing 100% of the waveform all the way up to clipping to be Class A.

    It's just that it is very uncommon to build amps this way anymore since SET amps are all the rage these days. But this was not uncommon to do back in the early 50s.
     
    SandAndGlass likes this.
  25. Marsman

    Marsman Member Thread Starter

    Location:
    Plymouth MA
    Sorry, what is good to know?
     

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