HELP QUICK MUST STOP HUMMING

[Sound Guy Paul]

Alright tonight I began recording with some of my new Christmas equipment. When we started I noticed a loud humming, that was not there when I was using my amp.(I was going Direct) I was using the following

Tuner-> ADA Midi Preamp-> Behringer Compressor-> XLR output to board.

Just now when inspecting the equipment, I noticed that the compressor XLR output has no Ground Lift/Ground switch. I am pretty sure this is the problem, but I do not know how to solve it. I need help and fast. Anyone have any suggestions on how to solve this problem?

[Mark Reccord]

OK. Start by trying to isolate the source if you haven't already done that. Start at the console input and unplug the output from the comp. then if the buzz goes away it's not the console input or the cable. Plug it back in and go to the input of the comp and unplug that. If the buzz goes away it's ahead of the comp, if it doesn't it's in the comp. Just keep going back through the signal chain until you isolate the source. You probably already know this but it doesn't hurt to go through systematically. It's probably just a ground thing between the comp and console. Here's a possible fix and these things are good to have around. Get a short length of mic cable and two XLR connectors. Solder the connectors on but leave the shield (bare wire, pin 1) unconnected on the female end. This creates a ground lift which isolates the grounds of any things that are connected by it. It's exactly the same thing as flipping a ground lift switch. This is a very useful adaptor. It will work in any balanced situation because the shield is only used to shunt RF and not as a signal reference. It won't work in unbalanced situations or if you have to pass phantom power because these things use the shield as a ground or reference for the signal. You may be able to buy one at a music store or PA rental house if you're not comfortable with soldering and building cables. You can also buy 1:1 line level transformers with XLRs, which completely isolates the two units. These are usually available at music stores and even Radio Shack. Really good ones cost a bit but decnet ones can usually be gotten pretty cheap (ie less than $20). You should have at least one of each if you're going to do any amount of recording. They are very useful. Hope this helps
cheers!