Inspired by the Beavis Board and other similar designs, I finally got around to building my own effects circuit test box. +9VDC in from an adapter goes to a MadBean RoadRage board, which uses a TC1044 and a voltage regulator to provide 9V, 12V, ~18V and -9V -- the leftmost knob is a rotary switch. Power then goes to a voltage sag knob before it heads to the outside world. I used a four-output speaker connection panel from Radio Shack for my connections to the external circuit. From top to bottom it goes: power, ground, circuit input, circuit output. The 1PDT switch is there to select whether circuit output or test probe output goes to the out-to-amplifier jack, but I haven't wired in the test probe yet. To test the test box, I connected an old BYOC Confidence Boost board I had lying around. Worked like a charm.