I have the mutant muff fuzz working (and am pleasantly surprised at the nice smooth distortion) and I started wondering about using Jfet's or Mosfet's in place of the silicon diodes I used, maybe 1 J201 and 1 2N7000. I'm wondering if it's worth unsoldering the SI's to try the Fet's? 8)
I think it could be worth it.
I've used FETs in fdbk loop distortion with good results.
Is it an Opamp Muff?
Yes, dual op amp. There are schemes and mods all over this place.