Cyg,
I bought this contraption from flea-bay for my Soldano Atomic 16 that is supposed to double the bass when replacing the green wire in the feedback loop. I was curious if you have: a) ever heard of anything like this before, and b) have any idea what would increase the bass in the feedback loop.
Here is a link to the item itself:
http://www.usacharvels.net/soldano_bass_boost.pdf
The amp sounds great when playing metal, but I cannot get enough bass out of it to get a nice warm, gritty blues tone when the gain is rolled back. I'm hoping this may help.