Another Class A/AB thread

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by drbob1, Oct 3, 2006.

  1. drbob1

    drbob1 Silver Supporting Member

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    OK, so technically a tube running in class A is biased so that it never reaches cutoff when the grid swings negative. With guitar amps, when you're overdriving them, you'd have to bias it really hot to get it to never swing that negative, but lets assume that you do (and set the signal amplitude to match). Doesn't that mean that the more positive swing of the grid is going to cause the tube to reach saturation very early? Meaning that you're going to have minimal clean overhead and a very asymmetrical clipping (which emphasized even-ordered, low order harmonics, right)? Is anyone actually biasing amps this way (see previous discussions about how even single ended amps-class A by definition-reach cutoff)?
     
  2. AdmiralB

    AdmiralB Silver Supporting Member

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    That rather depends upon the magnitude of the input signal. It might be enough to cause the power tube(s) to clip, and it might not.
     
  3. electroid

    electroid Member

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    In class A, the output tube will idle halfway between cutoff and saturation. When pushed hard enough, it will clip at saturation AND cutoff fairly evenly.
     
  4. AdmiralB

    AdmiralB Silver Supporting Member

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    It should idle halfway between...but it doesn't have to. It could idle towards saturation, it would clip sooner but would still be conducting for the full 360 degrees.
     
  5. AdmiralB

    AdmiralB Silver Supporting Member

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    Dude. We're arguing about guitar amps. When did anyone - manufacturers especially - ever get very concerned about specifics?

    "Why spoil the beauty of the thing with legalities?"
     
  6. AdmiralB

    AdmiralB Silver Supporting Member

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    That was humor! Try it sometime!
     

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