Mmmh, I'm not convinced, but I'm definitely not the expert, here. I guess I'll have to find either a 2A PSU or buy two 1A PSU. Bugger! Physically speaking, I was thinking of having the various signal jacks on the left side of the unit, while the MBHP modules (and related LCD and 7-segment digits) would be to the right. I'm not quite sure where I should put the relays, though; I'm thinking with the signal paths, to the left, but this is the part of the design where both worlds connects... I was thinking of connecting the loop outputs to ground when they have nothing plugged in (I'm not sure this is feasible with only TRS, though). This way, no need to warn the PIC about it. Or I could wire the relays ground to the TRS, so that it would have no ground if nothing is plugged, which means that it won't activate, and the signal will bypass this particular loop. The only caveat is that this means that the audio signal and the relays power supply share the same ground. Any thoughts? The expression pedal inputs definitely need to be grounded if nothing's plugged, that hadn't escaped my attention :) As for channel switching, I don't think this is actually a problem, since this isn't something we hear, and having nothing plugged won't bother anyone. I was planning on using transistors for this, by the way, because they're cheaper than relays and this is not in the audio signal path. The CORE has its own regulator, so that's covered. I'll definitely add a regulator for the relays, now that you mention it. But I'm not sure what you mean about the audio path. There is nothing in the box that changes the audio signal, so there is no component (aside from the relays) that needs any kind of power supply.