Okay, this is a confusing ordeal, I will try to be as clear, and simple as possible. Last week at my bands gig, I got an awful hum from the recording DI out, which I normally send to the house with no problems. It sounded like having your instrument cable unplugged, and holding your finger on the end. The sound guy we used was a new guy, and while a nice guy, knows zero about the stuff. We were more or less renting the rig, and doing sound ourselves. The PA, and bass rig were plugged into the same circuit, I am sure of. When I started diagnosing things, I pulled the instrument cable out of the preamp, to eliminate any possibility of a problem there. I tried muting the preamp to see if it would fix it, nope. I also hit the ground lift, to no result. I ended up getting a signal out of it, but it was very weak, and the hum was too bad to use. We tried 3 different channels in the board, and 3 different mic cables to connect it, with no difference. Here's where it get's tricky, there are 3 XLR outs coming out of the navigator; Right, Left, and recording DI out. I use the left side out to go to my rigs power amp. I unplugged it, and no matter which one of the three you plugged the rigs power amp to, it was fine, no issues. No matter which one you sent to the house, it buzzed like crazy. 10-15 minutes after start time, I gave up on going through the house, and gave my 210XLT a bit of a workout on the night. All I can think of is some kind of possible ground problem between systems, but I don't know. You would assume that my rig would get the same buzz on it's own if that were the issue. I asked meathead if he happened to have phantom power on from the board, he looked at it, clicked the button a couple times, and said no, but I have no idea. I have my whole rig here sitting in front of me, and can check things out if anyone has a suggestion, but I have nothing to plug the DI into until we gig again. I guess I better bring my 410xlt, a mic, or a DI box. We have played at this club numerous times, and while every time something seems to blow up, this is the first time there has ever been a problem with my gear (sticks outlet tester in gig bag).