Strange ground loop...?

Bob - what do you mean by "coax interconnects"? Are you talking about digital cable?

IC shield is grounded at one end only (if it's RCA). Try to reverse one that gives you trouble.

"If the cable is coax, the shield connected at both ends of the cable."

Bob - I was talking about interconnects.

"I don't get it... at all. What gives? If it's a shielding problem, then shouldn't configuration A-B-C-D also work just as well?"

Shield should be grounded on the receiving end (in my opinion) so your configuration D-C-B-A suggests that terminals C and A have shield grounded.

Bob - I asked since I've never had coax interconnect. Grounding shield on both ends is really bad, using shield as return is even worse. In addition coax cables, used in video applications, have not the greatest copper since at high frequencies signal travels only on the surface (often silver plated). Blue Jeans cables can still sound great (I don't question that). Capacitance, they are so proud of (12pF/ft) is nothing special (typical for polyethylene) since best cables have 3.5pF/ft and my cable has 5.1pF/ft. In order to get this capacitance foamed teflon in oversized tubes is required but it's expensive.

I am not talking about ground loops. If transmitting end (let say preamp) has ground/case at different potential than power amp's ground/case then it places this potential on the shield. Shield couples this difference (AC) to signal wire (referenced to different GND). When shield is grounded on the amp side then it has exactly the same level as the reference level of the signal wire and doesn't couple anything.

Djembeplay - I did not read your posts about cables carefully. If it's Blue Jeans cable and is grounded on both ends, like Bob says, then switching cable direction wouldn't make any difference.

It is difficult to find something in this price range (and I don't have a lot of experience). You might be able to find used AQ King Cobra (previously Python). It is very nice and neutral cable.

Bob - It makes sense, but why reversing interconnects makes difference? If it's BlueJeans then it's grounded on both ends and reversing it would not make any difference. He says that in one configuration of ICs noise is gone.

Why is it only in one channel - ground loop should affect both channels. Something is fishy here. Could it be defective cable? He mentioned that switching to Monster Cables eliminated noise completely.

"I just hooked up a long run of crappy RCA cable from the analogue outs of my PC." - quality of the cable is probably not important but this crappy cable probably doesn't use shield as return. Try the same cable from the DAC.

Djembeplay - I'm still not sure that cable was the problem. In general using shield as return is a bad thing but in case of hum or interference we enter the area of "black magic". Bob is right about your problem originating in unit being plugged into different outlets but the certain cables can exaggerate this effect. Why can't you plug everything to the same outlet?

"Anyone? What is a cable that has a return through the shield?"

- That's cable with only one wire (signal) inside and shield serving as second wire (ground/return). Coax cable is an example (BlueJeans cable is made of coax cable).