Many replies here. Many, many thanks. I really appreciate it.

Originally Posted By: Guitarhacker
When you installed the software, it's very possible the mixer/control panel also installed but you didn't notice it because if it's like mine, it didn't create a desktop icon.

Look in the start menu and check for a folder named for the interface or something very similar. Open it and look to see if there's an executable in there. That's where my control panel was hiding. You can create a desktop icon from there.

Interesting idea, but it didn't work in this case. I could only find two folders: one contains executables to uninstall and reinstall, the other contains two DLL files. I don't think this interface has any kind of software based control panel.

Originally Posted By: Jim Fogle
Open your Windows audio settings and check the balance for all your playback settings. Typically you can get to these settings by clicking on the speaker icon in the bottom, right corner of your screen or through control panel.

That doesn't help either. I don't have the problem when using the internal sound card, I just have it when I use the USB interface.

Originally Posted By: rharv
First and easiest test to clean them is to twist it back and forth a bunch. Just spin it left/right a bunch, then reset.
If 'dirty' is heard or noticed a spray cleaner may be in order, along with some more twisting back and forth.
But I'd start with twisting each dial back and forth a few times and then returning to original position, and checking.. Have the speakers/headphones on at the time so you can hear if one of them is getting dirty (you'll hear it when you turn it).

Originally Posted By: sslechta
Yup, before I gave up my last mixer if I had a knob that would start to get noisy I sprayed cleaner on it and turn it up and down about 100 times until the noise went away.

That makes sense and sounds like the best lead. I will have to go out and see if I can find that spray cleaner, and give it a try. I'm just unsure about it because the knobs won't come off and they don't look like they will allow any liquid to get into their shaft wells easily enough. But I will try.

Originally Posted By: sinbad
Have you tried cleaning the headphone output jack?

No, I haven't, and I've never heard about that. How does one clean an output jack? Is there some particularly appropriate brush or swab for that kind of job?

Originally Posted By: Charlie Fogle
(...) If the above is true, that indicates the problem is isolated to the headphone circuitry. There is likely an internal bias adjustment that would take any TV/CB type repair shop longer to get access taking the case apart than to repair. Likely cost if that's all they find wrong will be their minimum bench charge. Certainly cheaper than replacement cost.

I hope you're wrong, but you could be right. I will try the cleaning first before I resort to... uh... surgery. frown