ground loop with BH amps

[denti alligator]

As documented in this thread
http://bottlehead.com/smf/index.php?topic=9825.0

I have a ground loop problem with my PC and amps (SEX and Stereomour). I get some nasty PC noise over USB. Lifting the ground on the amps takes care of the problem, but I'm told that's not safe. What are my other options? Is there a way to ground the USB before it gets to the DAC (I've tried two different DACS--even turned off I get the same noise)? I assume the amps themselves are grounded well enough on their own? At least, I've never had this issue before with other sources.

One question is: could I use a cheater plug and run a separate ground from the amps to, say, the PC case or some other grounded device nearby (such as the CD player)?

Any help would be appreciated.

[Paul Joppa]

The problem is (probably) that the computer generates noise on the USB ground. The noise current drains to the safety ground at the power amp through the USB cable and the RCA interconnects. The cables and connectors have some small but not zero resistance, which converts the current to a voltage that is effectively in series with the music.

There are "USB ground isolators" - google that phrase. I got 377,000 results when I did. They are not expensive.

[denti alligator]

Thanks, Paul. Most of the USB ground isolators I've found are limited in speed, and probably couldn't carry the DSD signal I'm sending through it. Still searching...

What other options are there? What if I ran a ground wire from the tab of the 3-to-2 prong plug to the PC case or to some other ground? Or what if I ran a wire from the SEX ground to the PC case. Wouldn't that protect me from any dangers ungrounding the amp might put me at risk to?

[xcortes]

Heve you tried connecting the chassis of the dac to the chassis of one amp?

[Jamier]

Sam,
I don't know if this will help, but the Jensen Transformer site has a section devoted to isolating ground loops.

Jamie

[denti alligator]

I got the ifi iDefender 3.0. And it works! The crazy thing is that one of the very first things I tried was the ifi iPurifier, which did nothing. If only I had consulted with them when I returned it.

[johnsonad]

Good info, thanks Sam! I find iFi to be extremely helpful.