Via.
I put this together to tweak the 2A03 sound control system. It is essentially several processors and some buffering. Some parts are interconnected, and others are broken out into pin headers. It is powered by a standard 9-12V DC walwart, has two 1/4? output jacks (one for each set of channels), and includes MIDI input circuitry. It’s a little big at 6? by 6?, but the point is to make everything easily accessible by hand.