JFET Vulcan Bias problems

[Michael Allen]

I built the JFET vulcan and can't get it to sound good. Built according to schem with J201s, .001uF output cap on first stage, .01uF cap to ground after 2nd stage output, and SWTC2 after diode before 3rd stage. 2nd and 3rd stage have 10uF caps from source to ground.

I have all the JFET biased between 4-5V yet the signal still sounds misbiased. I've audio probed up to the second stage and the sound is fine, biasing each JFET until it sounds good. Voltages are like 4.2 and 4.6V. Gates and Source are all appropriate. Then I get to stage 3 and no matter how much voltage is on the drain, it sounds clamped. I can hit a chord and it sounds alright, but when I start playing solos the sound clamps if I play fast enough.

Tried taking out the tone control, putting it back to stock, and same issues. Replaced the diode and same issue. Not sure what else to try, the 1M and 10M are correct value as is the 39K.

Any idea what could make the last JFET sound bad like this?

[aron]

Are the voltages correct on the last stage? Is the diode oriented correctly?

[Michael Allen]

yeah, diode in the right way

all JFET have ~the same voltages

D. 4.5V
G. .9V
S. 1.4V