AMZ MosBoost - Make it dirtier?

[Jaicen_solo]

Anybody have any suggestions as to how I can make an AMZ Mosfet booster a little grittier.
At the minute, I have a nice clean sparkly boost that sounds great into my modded GA-5 (Valve Jnr).

However, it's intended to be used in front of a clean Fender deluxe.
Is there any way to mod the design to have a little more harmonic richness (like a Rangemaster, without the treble boost), without sounding like an overdrive? I know I could mod a Rangemaster, but this pedal is built, and needs to be ready tomorrow. It will also be used at the end of a pedal train including digital FX, and I know a Rangemaster doesn't like that.

[CurtisWCole]

I could be WAY off but maybe increasing the value of the Gain pot. Maybe to a 10k or 25k.

[Jaicen_solo]

Hmm, I don't think that would work, because the gain pot produces maximum boost at minimum resistance.

I was thinking more along the lines of altering the bias so that part of the signal is clipped with large signals.

[Ben N]

I wonder if altering the bias would produce the nice added harmonics you seem to be after. At the cost of some volume, have you thought about tacking a pair of clippers on, Electra-style?

[Jaicen_solo]

Yeah, tried that but there was no output. Tried them with a cap in series but there was no audible change.

[Projectile]

Changing the gain pot won't give you any more gain. It's already maxed. You could adjust the bias so that it is way off center and produce some asymmetrical clipping that way.  I'd probably try making R5 and R1 smaller. You have to adjust these two resistors in conjunction (or make R2 larger instead of R1 smaller). This will lower the DC voltage at A, which is what you want. You just want to make sure that A is getting lower in proportion to your voltage divider adjustment, not as a result of turning off the mosfet.