I recently purchased a new Logitech z906 5.1 speaker system to replace my aging X-540 speakers. When I connected everything to my PC using a Sound Blaster AE-5 card (using the 3x3.5mm analog outputs), I got a hum in my speakers that became very audible anytime the volume on the Logitech control pod was turned up past 3. The higher I turn the volume knob up on the control pod, the louder the hum gets. Increasing or decreasing the volume on the source itself (my PC) doesn't change the hum at all and turning the PC volume up usually drowns it out completely. I tried different cables, with the same result.
I connected an optical cable and the sound is perfectly clear with no hum whatsoever. I would prefer not to have to use optical though, so I continued experimenting. I connected another source via RCA audio and there was no hum on that one either, so it is specific to the analog outputs on my PC sound card. At that point, I decided maybe there was a problem with the shielding on the sound card and I ordered a brand new AE-7 card. I installed that, and I'm still experiencing the exact same hum, which seems to rule out the sound card itself. What else could there be? Maybe a ground loop? If so, would it be possible to put a ground loop isolator on each of the 3 analog outputs coming out of my sound card? Is there anything else I could be missing?
I connected an optical cable and the sound is perfectly clear with no hum whatsoever. I would prefer not to have to use optical though, so I continued experimenting. I connected another source via RCA audio and there was no hum on that one either, so it is specific to the analog outputs on my PC sound card. At that point, I decided maybe there was a problem with the shielding on the sound card and I ordered a brand new AE-7 card. I installed that, and I'm still experiencing the exact same hum, which seems to rule out the sound card itself. What else could there be? Maybe a ground loop? If so, would it be possible to put a ground loop isolator on each of the 3 analog outputs coming out of my sound card? Is there anything else I could be missing?