Covert overdrive sounds not only woolly....but unbiased

[ferdinandstrat]

I saw the thread regarding the capacitor mods and will perform it, but I had another issue that was bothering me. The distortion sounds slightly unbiased, has anyone encountered such and issue? I tried several Jfets such as J201s, MPF4393(which I verified by building a Bohemia) and 2N5458s

 

[Chuck D. Bones]

This circuit is self-biasing. Using different FETs will affect performance. I used MPF4393s in mine and it sounds good. If you measure and report the source voltages on all of the FETs, then we can evaluate whether there really is a bias issue. Have you verified that all of the resistors are the correct value? The cap mods will improve the frequency response, but won't change the distortion.

 

[ferdinandstrat]

As far as I know the only values that were different were the 2M2 voltage divider resistors for the last gain stage

I will measure the voltages for the sources and report back