Tube Amps / Music Electronics
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|previous: Steve A. Rick:||View Thread|
|11/27/2000 9:46 PM|
|Bruce||Re: Bedrock MV|
First off the only reason to do this is for more preamp distortion.
If you use a dual gang 250Ka pot and wire the wipers to the PI/Driver coupling caps, the top of the pots to the grid stoppers, and the ungrounded part of the pots to the bias supply feeder, you get a fixed bias grid load resistance equal to the value of each pot while the wiper sends some of the PI/driver signal to ground through the bias supply filter caps and B- supply as normal or if desired because it is now variable, on to the grids of the power tubes.
Theoretically, the power tube's grid are still at the same -DC potential and the wiper is now the driving element from the PI/driver so you can run it way down and loose quite a bit of the PI/Driver signal and then turn the volume or drive controls prior to the PI/Driver way up to compensate... more preamp distortion.
|Steve A. Bruce:|