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PI values for Class A push-pull

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  • PI values for Class A push-pull

    Can someone provide some info on PI resistor values for a 5E3X2 that I've modded to run in Class A? I have the tubes at 300v on plates and 42ma current. The PI is apparently feeding too much signal into the power amp thus it is still clipping/cutting off.

  • #2
    Something around 190-200 Plate and 50-55 cathode for the PI, 140 plate for the driver and 110-120 plate for the 1st voltage amplifer stage.

    If the pre-amp voltages you've got are too high, then up the pre-amp sullpy resistor (try 27k or 33k - instead of 22k)

    However, I wonder if you have built it to run 300V on the plates, then maybe the pre-amp isn't getting enough power? (- in which case you can reduce the value of the pre-amp supply resistor - try going from 22k to 18k)
    Building a better world (one tube amp at a time)

    "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

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