steve wrote:You can also try the Ice Cube mod, which uses the reverb circuit driver as an overdrive. A crude version of it is to just jump the reverb send and return jacks with an RCA cable, and then you can use the reverb knob to adjust the gain of the overdrive and switch it in with the reverb footswitch.
My friend Neil has one of these on his silverface Twin and it's really effective. It sounds less like a natural crunch effect and more like a 'zingy' kind of EQ boost.