Here's another version of the Calico amp mods. This one only has two primary flavors by switching a .022uF Orange Drop cap into parallel with the .0022uF Mallory 150 in C1. C2 remains fixed with a .022uF Sozo cap. It has variable NFB and C3-lift on a toggle switch, foot-switched preamp bias resistors, as well as an input impedance switch and an fx loop. It also has a variable slave out on the back. This amp is a well rounded and relatively firm fatty thanks to the 2uF cathode caps in C3 and C4. There are 1M resistors in R6 and R7 to preserve sparkle and brightness (for the BitMo tone pot which you won't see in the schematic).

Gil...