Re: Hum

You have a ground loop. Your PC is grounded, and there is probably something in your stereo system which is grounded as well. A CATV cable connected to your TV/VCR/Receiver would be an example. You need to break the electrical path to solve the problem. You could use a transformer coupled line-level isolator with some loss in signal quality (maybe not too critical since you are playing MP3s). I think Radio Shack sells one of these for car audio applications. A more high end solution is to just run digital audio from the PC to the stereo. This comes in either an optical (TOSLink) or co-axial flavor (transformer coupled) and is electrically isolated in either case. You can also run it a long distance without any signal loss. This is what I use and I'm very happy with it.