Tube Amps / Music Electronics
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|previous: john hermsen Hi there,||View Thread|
|5/5/2000 8:00 PM|
|Jim S.||Re: homebrew bias question.|
The values of the bias feed resistors have virtually no effect on the bias voltage on the control grids of the power tubes. They should have the same value, however.
Chances are, your power tubes are not well matched. To make sure this is the case, you should measure plate, screen, and control grid voltages on all of the tubes (at idle) and make sure they are the same from tube to tube. If so, then it's definitely the tubes and not your circuit and I would suggest either: (1) installing a set of output tubes that are better matched, or (2) installing two bias adjust pots, one for each push-pull side (feeding separate, non-connected bias feed resistors). By the way, (2) is the only proper way to compensate for mismatched output tubes.
|john hermsen hi,|