I'm interested in building a footswitch for my 1975 Fender Super Twin amp, but information is very hard to come by. From what I've been able to gather, the original footswitch had stomp buttons for punching the 5-band EQ in and out and for turning the distortion on and off. The unit also had a slide switch that activated a volume boost in conjunction with the distortion footswitch. Here's what the footswitch looks like:
I'm hoping one of our resident Super Twin owners/fans might be able to give me some gutshots of their footswitch, or just some more info.
I've tried contacting Fender and they were kind enough to send me a schematic for the Super Twin
Reverb, which they said was very similar. They did not have a schematic or other info on the footswitch, aside from some part numbers. From looking at the Super Twin Reverb schematic, it appears that the ring to ground connection on the distortion/boost tip-ring-sleeve (TRS) plug is in series with the amp’s distortion switch. Inserting the plug opens the path to ground, and then the footswitch closes it.
The boost is a little more complicated. I’ve read that the boost switch inserts a 39 ohm resistor in parallel with the 100 ohm resistor in the negative feedback circuit, so it's not a simple open/close stomp switch like most amp pedals.
My eventual goal is to build a two-button footswitch, controlling EQ and boost, and ignoring the distortion “feature”. I've attached a copy of the amp's schematic. Any help out there?
