used my SC-1's live last night for the first time..as mic pre's in front of a Yamaha M7CL digital console at a 700-seat venue here in SF. In testing them out I made an interesting discovery - when the top panel of the rack case is removed, almost all of the AC hum goes away. When the panel is placed on top of the case, the AC hum gets amplified. (though even cooler is that it's loudest when holding the panel about 1/2" above the case, but not actually touching it.)
i just left the top off (that got some nifty comments) and ended up using it on the kick and snare mics....and got two comments from other engineers about the impact and clarity of the kick and snare - they didn't even know I was using any outboard gear.
but back to the issue - AC hum. I have two ideas here:
first, I could go nuts trying to figure out why it's humming, then develop and implement a solution
secondly, I could just make a plexiglas top panel