Currently have a problem with horrid speaker hum and I can only narrow down the problem to something with my computer.
Problem is that whenever I have my speakers (Logitech Z-680) hooked up either by digital (coax) or analog and I then attempt to connect a source that is not optical (i.e. another digital coax, or any two channel stereo like a Gamecube connection) I get a horrible hum on my speakers.
Its a steady single tone hum that elevates as I turn the volume on the control tower or move the volume on the computer volume control menu. As soon as I disconnect either the offending source or my computer the hum disappears. This hum does not appear over optical connections.
My sound card is a Audigy 2 Plat with live drive and a Soundstorm card on the Asus A7N8X Delux mobo. I have this problem with both sound cards. I have tried using the analog connection of both cards, and then the digital coax from the soundstorm. The buzz happens if I use the line-in on both cards or the line-in on the speaker control tower. Also happens when I try to run the line to the analog speaker connections on the control tower when using digital coax connect via my Soundstorm.
I have tried buying heavy duty 3mm and 4mm pro cables that are triple shielded thinking it was maybe interferrence of some kind with no improvement. I have tried moving my speaker control tower away from the computer as well, 12' to be exact with no luck. My speakers and computer are hooked up to a power supply unit that prevents the charge from being polarized on the electric line.
I have disabled alternatively the soundstorm and audigy 2 (even removed it from the system) to try and isolate a bad sound card but no luck. I have even tried pulling my entire computer apart and reassembling piece by piece and reinstalling all software from scratch with no luck.
Athlon XP 333 3000
Asus AN78X Deluxe
1GB PC2700 Micron 2.5CL ram
Seagate 120HD SATA Baracuda HD
IBM Deskstar 30GB HD
WD Caviar 40GB HD
TDK 48X CDR
GF3 Ti 64mb
Audigy 2 Plat with Live Drive
ThermalTake 480watt w/ PFC power
I have no idea what it could be and it drives me nuts as my main use for my PC is as a media center
Audible hum,usually means 50/60Hz, depending on your location. It is almost always caused by what one would refer to as "ground loop" conditions.
The best way to find the cure is to consider the name ground LOOPs carefully with respect to your connection scheme (especially the gorund connections and power). Ideally you want a star ground topography rather than a loop ground topography.
If what I just said seems to complex there is always the brute force approach which will eventually get you to the same place. The brute force approach is of course just try every possible connection scheme until you find one that works.
Point a suspecting eye at UPS's etc. and do stuff like testing with and without, plugging into different wall outlets etc.