I hope I'm doing this right. I checked the components in my recently acquired Gain Changer SR (PCB is labeled SR and V4) against a V2 gutshot found online and the 2012 schematic on Barber's site to find the component changes for the SR. I'll list only the components that have been tweaked:
Schematic Value | SR V4 Value
Input Cap:
.056uf | .022uf
Tone Section:
8.2k | 12k
16k | 27k
100k | 75k
3.3k | 3k
Second Op Amp:
7.5k | 6.2k
22k | 30k
All the other values are the same as the schematic.