Old Dual Rectifier footswitch build

[Jimi W]

I've got an early Mesa Dual Rectifier with a single button footswitch that switches between clean and dirty channels. It's been playing up recently, I think its just the lead between the footswitch and the amp but it got me thinking so a I decided to open it up.

Inside is just a spst switch, a mono jack socket and an LED. The LED has one lead to the tip of the jack and the other to the shield. Its obviously powered by the amp and I'm guessing the switching is done by a relay? Would this be correct? Could somebody explain what happens when you press the switch?

I'd like to build a new switch in a smaller enclosure, I'm just a bit worried that I don't really understand what's going on with the power for the LED coming from the amp and I don't want to hurt my amp!! 

If I was to build a new one is it just a normal footswitch I'd need? I'd prob use a spdt I've got in stock.

Cheers folks,
Jimi

[Alvarez]

 It should be just like sending the audio signal. base should be ground and tip should be hot. prolly a transistor inside that switches channels accordingly. (bs170 or so)