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Purpose of the "fizzy" (PI) cap?..

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by BluePat, Feb 24, 2009.

  1. BluePat

    BluePat Member

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    and by altering the value, what does that do?

    Pat
     
  2. RussB

    RussB low rent hobbyist

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    It's there to supress high frequency oscillations

    The higher the value, the more high frequecies will be diminished. In Marshall circuits, I have gone as high as 180pf and couldn't hear a difference from the stock 47pf cap. I could hear a 250pf cap
     
  3. BluePat

    BluePat Member

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    Thanks Russ :BEER
     
  4. cap'n'crunch

    cap'n'crunch Member

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    Whatz you guys talking about? My 2204 is fizzy at low volumes. Is this a remedy for that?
     
  5. donnyjaguar

    donnyjaguar Member

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    The capacitor reduces the gain of the amplifier at frequencies above its normal operation due to phase reversal through the output transformer. To my knowledge its not a "tone shaping" component and RussB's experiments bear this out.
     

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