For the semiconductor gurus out there...a question

Discussion in 'General Electronics Chat' started by KL7AJ, Apr 3, 2015.

  1. KL7AJ

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    I get a lot of top end audio amplifiers in the shop (everything from guitar amps to P.A. systems) that use the awkward quasi-complementary-symmetry output stage. The quasi-complementary stage was originally designed (according to legend) because it was difficult to build high power PNP transistors, so they had to fake the PNP side by using a pnp driver and an NPN output device (the 2N3055 still reigns supreme).

    My question is....with MODERN semiconductor manufacturing methods, is the "quasi" even necessary? Certainly there should be a complement to the 2N3055...or is there? Does anyone have an inside track on this.

    The quasi complementary symmetry circuit is an annoying circuit....not because it sounds bad...it just seems like a kluge. The true complementary-symmetry amplifier is...well...more symmetrical.

    I've been in the business for over 45 years and can't figure out why the quasi complementary circuit hasn't died a necessary death.

    Help me understand.

    Eric
     
  2. #12

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    I don't actually know if P type bipolars have improved very much in the last 40 years, but consider,
    Mfg's can do this in with fast switching mosfets in PWM mode...and cheaper, too!
    So what happens to their sales figures if they do?
    The audiophools would hang you in effigy, if not in reality, if you, "improved" their antique amplifiers.

    Just a few thoughts.
    Nowhere near a complete answer.
     
  3. nsaspook

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  4. KL7AJ

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    Alas...that device is obsolete
     
  5. dl324

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    Audiophiles are pragmatic when it comes to what's high fidelity and what isn't. I've heard claims that they can hear the difference between a wire with a soldered splice and one without. But then they like the sound of distortion caused by the carbon comp resistors in their tube amps.

    BR
    Dennis
     
  6. nsaspook

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  7. #12

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    I think you are confusing, "pragmatic" with, "hysterical". :D
     
  8. KL7AJ

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  9. crutschow

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    My motto is "If it ain't broke, don't fix it."
    If the quasi complementary circuit gives satisfactory performance then why change it just to be " ...well...more symmetrical"?
     
  10. KL7AJ

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    Because asymmetry is an affront to the universe. Well, MY universe, anyway. :)
     
  11. MrChips

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  12. nsaspook

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    "Per the manufacturer, more stock expected week of 6/22/15"
    It's not discontinued, if there was greater demand for the transistor then more would be made in each batch. Normally with older parts a production schedule is designed to meet future demand for say 6 months to a year. These old transistors are not hard to make so just about any junk 6 inch fab in China can make millions if needed.
     
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