I've got an Ampeg BSP preamp that has a 1/4" TRS input for the footswitch. I just got a basic Peavey two button footswitch for it and it works fine - in my case, one button is an on/off for the mute and the other is a channel selector.
Is the ampeg Afp3 suitable? There doesn't seem to be any information online for compatability? Any1 else using a foot switch for the svt4 pro if so which ones .