Ok, so a 7-pin DIN cable uses two of those for phantom power, I understand this.
...My question is, will a midi floorboard with a 5-pin connector (and an external power source) plug into and function correctly? I'm assuming the two missing pins are the ones used for power. The amp i'm getting (Randall RM100) has a 7-pin midi in/thru, and my floorboard is 5-pin. Can they play nice together?
Not as far as I know, the plugs are physically different and just won't fit together. Pick up a Midimate.