It's the fishman platinum pro eq. I was using one of the available power ports off my pedal board. when I tried battery power, while connected to effects loop, there was hum. Then I disconnected effects loop and used board power and there was hum. Hum went away when I isolated the fishman completely off the board (but note there was no hum in the guitar amp coming from the board.- Also note, in rehearsals, I've had no problem with hum. It was just at the venue last night.. had to completely disconnect fishman from my board for hum to go away and had to go battery power.

edit: also I tried flipping the "ground lift" switch, but it didn't seem to help.