Well there is a humming that is sometimes about as loud as the highest signal some programs will output on windows.
There are so many [originally temporary] interconnects on my system I just haven't been up to the task of figuring out the exact issue. Typically it is just my motivation for hooking the computer up with digital audio.
Is the computer in the same room as the system? If not, then you probably do have a ground loop. There's a tutorial on them on the main forum page. Ideally, the whole system will be on one circuit or at least the same phase of the service feed. The next thing to address is that there's no resistance on the ground conductors between the computer and the audio system. One way to eliminate the hum is by using an isolation transformer- the cheap ones work but can affect the sound quality. Jensen is one company that makes good ones but they're not as cheap as the ones from Radio Shack. The hard way is by working with the electrical system in the building to make sure it's up to code and to make sure the whole system in on the same circuit(s).
If you have cable TV, unplug the cable feed and if that eliminates the hum, you need an isolation adapter for that, not the power.
If you use an optical cable, you can't have a ground loop. If the computer only has a digital coax output (usually called S/PDIF), get a coax-optical adapter. As far as the optical cable- don't bother with anything that has gold plating- it's sending light and the gold will do nothing to help anyone but the seller and manufacturer.
