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previous: anon A MV circuit across the PI has to b... -- 10/28/2000 7:01 PM View Thread

Re: post PI volume on one side only?

11/2/2000 8:06 PM
Rick Erickson
Re: post PI volume on one side only?
"A MV circuit across the PI has to be on both sides as it works by cancelling the audio signal since the sides are out of phase. If you use the MV in the bias-splitter position, cutting one side will still sound like YAK since your amp is almost certainly class AB and one tube does not recreate a whole wave.. "
Just had to share this - I'm working on an early Bedrock amp and the MV is a post p/i type 250k dual. The kicker is that they used a Z taper pan pot. This pot pulls one side of the p/i down before attenuating the other, forcing the p/i into asymetrical distortion, presumably enhancing second order harmonic distortion components. They also wired it so it forced the output of the p/i to ground. Plate load resistors are 100K & 200K. Very strange, but it does prove that not only can it be done, it already has!  

Rick Erickson [QUOTE]Plate load resistors are 100... -- 11/2/2000 8:07 PM