Read about ground loops here: http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz
Cheers
Richard Howey
Audio Dynamite Ltd
IDR48/IDR16/T112/R72/Mixpad,Tweak,
Dual M-Dante/DVS, 17″MBP/Logic 9/Custom Mackie Control
