Sharp static noise from Monitors

[tgod1811]

I get this sharp static noise from my monitors that only happens when I'm changing the volume on my fast track. It actually hurts my ears.
I have a pair of HS50s going into a krk 10s sub (XLR to XLR), that goes into my Behringer 502 mixer (XLR to TRS). The mixer is connected to my fast track usb via the radioshack groundloop isolator --->(http://forums.klipsch.com/forums/sto...io%20Shack.jpg)

The fast track goes into my laptop via usb. I know nothing is wrong with my monitors because my KRKs had the same problem. The guy I sold the krks to didn't mention any static noise. What could be causing it?

[jwl]

Sounds like a scratchy pot (volume knob) perhaps? Could also be a grounding issue, but regardless the issue is certainly electronic. Try a different volume control technique/unit and see if the problem is affected.

[tgod1811]

Certainly has to do with the m audio fast track because the mixer knobs do not cause the problem.

[DanDan]

You have Behringer and RadioShack at play....
What could possibly go wrong....;-)

Disconnect everything except the FastTrack and Computer.
Headphones. Scratchy noise still there, the problem is obviously the FT.
If not, move on slowly. Behringers and such can put out DC on their inputs!
DD

[tgod1811]

The static noise when turning knob is still there when I disconneted the mixer and only used headphones on the fast track. But the noise was very quiet and didnt seem like a problem.
From my understanding, either my fast track or behringer has gone bad. I may just sell both and get a fast track pro, it would do the job of both.

[DanDan]

That sounds like DC coming from the Behringer Inputs. Are you going in on XLR? Phantom? Some of these little desks use the same circuit for the TRS or Jack in. Put a Meter on it and see if there is DC.
DD