Originally Posted By: Ryszard
Thank you all. I have several things to try now. Some are from checking the PreSonus site. It is not complete, and they are in no particular order.

1. Replace the USB cable.
2. Make sure it's not plugged into a USB 3 socket.
3. Isolate the PC. (I may try a ground lift there.)
4. Reroute control, power, and signal lines as appropriate.
5. Replace the sound card. (That would be kind of okay since I'd like to upgrade to one with a S/PDIF output so I could use the Focusrite(?) VRM speaker emulator with my headphones.)

There is more, but this will keep me busy for a while. I'll keep you posted.

For the most part this sound reasonable, BUT, I am very uncomfortable with #3. I hope you are not considering a MAINS ground lift. IMHO that is potentially a very dangerous thing.

FWIW I'm ALWAYS nervous when people start talking about lifting pretective earths from inside mains powered equipment. Double insulated is one thing, but your PC has a metallic case.

--=-- My credo: If it's worth doing, it's worth overdoing - just ask my missus, she'll tell ya laugh --=--
You're only paranoid if you're wrong!