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RE: Fixed, cathode, and back bias

"Shared bias, whether fixed or not, calls for matched tubes and low DC resistance in the grid circuit. A great example is transformer coupling between the driver and power tubes. "

Amen. I have power amps that run four KT120s PPP with shared bias provided by a single CCS (no bypass cap, Class A differential). The output stage is coupled to the driver with an IT. I tried using two cathode current sources and a cap as described in above post. While this arrangement has the advantage of maintaining DC balance, I didn't care for the coloration the capacitor added.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln


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