AMZ Mosfet Booster mod idea. Will it work?

[masinyourface]

I just had the crazy idea to experiment with diodes on the source side of the mosfet in an AMZ Mosfet Booster, particularly in series or in parallel with the bypass capacitor. Unfortunately I'm not free to experiment until this weekend. Is it worth trying? What kind of effect should I expect on the sound?

[antonis]

You'll alter MosFEt's bias..

Possible combination cases:

A pair of back to back diodes in series with cap -> It simply adds an extra Vfd on top side of gain pot (you'll not be able to get max gain..)

One diode in series with cap -> It blocks AC gain at "reverse" placement and a acts as above at "right" placement (asymmetrical boost..)

A pair of back to back diodes in parallel with cap -> It shunts cap and place the gain pot in parallel with Rsource at DC (you'll almost have the same DC & AC gain..)

One diode in parallel with cap -> Same as above but only for the half waveform - (asymmetrical boost..)

[Transmogrifox]

This will generally introduce an effect like crossover distortion.  These things are worth a try, but most likely you will get a fizzley sounding blat when you strum hard or cause the bias to shift to the point where you either get blats or nothing at all.

The back-back diodes in parallel with the cap will forward bias through the gain pot and you will have something similar to an SHO...except the bias will change so extremely that at low resistance of the pot the MOSFET will be completely saturated and you won't get any sound out at all.

One thing you could do that would be different than crossover distortion is this:
9V-10k-1k->GND
Take a diode from between 10k and 1k to the gain pot.

This looks like an AC impedance of something like 1k for negative-going signals.  It looks like high impedance to positive-going signals (shuts off diode as it goes positive).  Then you would have an asymmetrical boost for which you can adjust the effective diode drop.

If you just put a diode + resistor parallel to the gain pot you could have an equivalent effect except your input guitar signal needs to be >300 mV peak to even turn on a Schottky, even more to turn on a Si diode.

My recommendation pre-biases the diode so that it does not require as much voltage fluctuation to turn it on and off.  You can play with the resistor ratio as well as the resistor values to get different amounts of asymmetry.