I've just ordered two Fender 2x12 combos that use this footswitch: Fender 2 button footswitch
I'd like to control both amps with the one footswitch - should this be possible by simply splitting the signal from the footswitch using a TRS stereo splitter?
I'm not sure how footswitch signals work, but considering they're sent (in this case, at least) via a 1/4" patch cable then it can't be very complex. Not like splitting an RJ45 or MIDI cable might be.
Footswitch cables are wired usually very simply. Nevertheless you should not try using a Y-splitter here. There are two reasons:
a) you don't know the behavior of the open switch on the amplifiers. If both amplifiers have the exact same circuitry, connecting their "open" switch signals should not cause problems but nobody gives a guarantee for that. If you have different amplifier models, all bets are open.
b) you'll get a ground loop. Those are, like, really bad news.
That does not mean that you are out of options. Take a look inside of the foot switch: do the switches have an unused set of connectors? If so, you can root out another pair of (ground-isolated!) sockets from there. This will avoid both the ground loop as well as the "open-together" wiring problem.
Other than that, you'll have to wire your own "relais box" "talking" to the foot switch on one side and (via isolated and separate contacts) to the amplifiers on the other side. Or you build a box of your own. Or you just change the foot switches in your existing foot box for double-contact ones and then use the separate ground-isolated socket approach.
I'm guessing that the plug going into the amp is TRS, not standard TS. It needs to be, to control two different aspects. Indeed, the two switches may not even work the same as each other. However, since the pedal is to work two amps that are identical, there will be a way. What you'll need to do is make up another lead the same as original, with TRS plug, and solder the terminals inside the pedal in the same configuration as the original plug. An A/B/Y converter probably won't do the job.
In the case of these Fender Champion 100 amps, they use a mono (TS) cable fed by two switches: channel toggle & FX on/off. A simple Y-splitter cable (TS 1/4" Male to 2 TS 1/4" Female Plugs) works like a charm with no hiss, hum, or discernible issues.
I'm guessing this is not a blanket solution when disparate amps are involved, but as far as controlling these two identical Fenders it was indeed as simple as the Y-splitter cable.
