I have a funny buzzing issue. In our Youth department's sound set-up, we run all of our A.V stuff into a switch box, then into a Mackie Board on one of the stereo channels. In the A/V Switch, we have a VCR, DVD, CD and a desktop computer. When the Switch box is on the computer, and the fader for the channels, mains, and sub-group are all on, we get NASTY buzzing. It's the only time we get that sort of buzzing going on. Here's the set-up: PC -(1/8" - RCA)-> Switch Box -(RCA - 1/4" TRS)-> Ebtek Hum Eliminator -(1/4" TRS - 1/4" TRS)-> Channel input. We're using a Mackie CFX 16, a Dell Dimension 4700, and a Radio Shack 4-channel A/V switch. Any thoughts?