Q: The manual for my RJM Music Effect Gizmo/MasterMind says that I can power the foot controller (the MasterMind) using a 7-pin MIDI cable. I thought MIDI cables only had five pins, and that two of those were unused. What’s up with that, and where can I find such a cable?
A: Sweetwater to the rescue! This is the cable you’re looking for: the Hosa MID-725. It’s a 25-foot long cable that has 7-pins for use with MIDI controllers and devices that can be powered using a 7-pin cable.
You’re correct that the MIDI spec dictates a 5-pin cable, with the outside two pins unused. This is a non-spec cable, but there’s little danger of plugging it into the wrong thing or interfering with “regular” MIDI, as only devices that can use it will have the corresponding 7-pin DIN jack required.
You can also power the MasterMind with its own power supply, and use a regular 5-pin MIDI cable to connect it to the Effect Gizmo. There is no difference in performance either way.