Computer noises carried through USB cable to soundcard and speakers

[Nyrrth]

Hi guys,

After doing a fair bit of troubleshooting, I've realized that the sounds produced inside my mid-2011 21.5" iMac (power supply, circuits, etc.) are being transmitted through my hi-speed USB 2.0 cable into my audio interface (Roland Octa-Capture), and out my powered speakers (KRK Rokits). I hooked up my Macbook (much older model), and the sounds go away, with everything else being the same.

Has anyone else had this issue? If so, how did you get around it? I've heard that using a powered USB hub can fix this, and I also know of optical USB extenders that may do it (although they cost more than the interface itself, which is pointless). I also believe there are some galvanic isolators out there, but from what I know, they only support up to full speed (12 Mbps) USB and not hi-speed (480 Mbps).

Your help and insight would be much appreciated! The sounds are driving me nuts. Each time a page loads, I move the mouse, etc. I hear the corresponding sound in the form of hisses, crackles, squeals and the like.

Thanks!

 

[Nyrrth]

Alright guys, looks like no one had a solution. But I found this little gadget online which I was able to purchase from Amazon: Ebtech - Audio Solutions

Plugged my iMac into it, plugged it into the power outlet, and no more computer noises. So definitely a ground loop issue. I have Apple Care, so I will be taking it in for them to check out any ground loop issues, but for now all's well. If anyone else has a similar issue, give it a shot.

 

[lava]

I've had this problem. A three-prong to two-prong adapter will take care of the issue. However, what you bought is better because you still have your earth ground.