Lawrie,

1. I should have spelled #3 above. I meant the video card (VPU), not CPU. IT's a Zotac 560 2-Gb card.

2. Signal goes from back panel USB port—which MAY be USB 3, I don't know how to tell—to PreSonus AudioBox (PAB) USB. Signal also comes from Behringer 16 x 2 mixer to PAB preamps. Signal comes out of the PAB to (a) Behry 4-ch. headphone amp, and (b) JBL PSW-D110 sub ins, and out of Xover to (c) Behry TRUTH B2031A active two-way monitors.

Note: It ain't the speaks. There is abso no noise when the PAB us D/Ced from USB. The mixer has also been positively ruled out as a source.

3. I have no idea how to lift ground in the signal chain. Please say more.

R.

"My primary musical instrument is the personal computer."