If you're using a laptop the ground loop is pretty much a given. But you are talking about a PC sound card.

Another potential source of hum twixt PC and PA is cheap audio cables. I had a nasty buzz coming from my DAW into my studio system until I trashed several 22-gauge Y-cords and multiple adapters for heavily-shielded brand-name home-theater grade AV cables. No more electrical noise. (And they look really cool!)

A surge protector with EMI/RFI filtering is a good idea, too, to keep hum from coming in on the AC line.

R.


"My primary musical instrument is the personal computer."