We’ve had a lot of people over the years ask questions about MIDI cable wiring.
Looking at a MIDI cable, you will find the pins arranged as shown here:
O….. Pin 1 (No Connection)
O……… Pin 4 (+5V DC Voltage)
O………… Pin 2 (Ground/Common)
O……… Pin 5 (MIDI Data – Hot)
O….. Pin 3 (No Connection)
This diagram technically only applies to MIDI outputs and thrus. A MIDI in is slightly different, but not in any way that would affect cable wiring. A working MIDI cable can be made by connecting only the three center pins (2, 4, and 5). In fact many MIDI cables only have those three pins connected. The +5 VDC on pin 4 is where self-powered MIDI boxes get their supply voltage. Some MIDI equipment has been known to use pins 1 and 3 for other functions so watch out for that (more info in the 4/7/97 TTOTD). It is also possible (though we don’t officially recommend it) to use those two unused pins to carry other power (for things like remote keyboards) and/or audio signals. This generally requires modifications to the equipment and will, of course, require MIDI cables with all five pins connected. Don’t try it unless you know what you are doing. We may get in to some of these details another time.