SPDIF Earth Loop

[noodle_snacks]

I have an SPDIF out on my computer, my reciever is double insulated so had no problems, and my subwoofer amp had a ground lift switch so no problems there either, I added a behringer feedback destroyer for parametric bass eq, now i have an earth loop problem between my computer (through the SPDIF cable, to the BFD). What is the best way to fix this? (Can i use an isolation transformer with a spdif cable perhaps?)

[mrshow4u]

you can use a C-02 from M-Audio for electrical to optical conversion, or get a digital transformer. Pulse Engineering makes them. I think Mouser had them. PE6512 TOSLink gets lame at 192kHz, and the transformers aren't really spec'd above 96kHz. The transformers do continue to work at 192 kHz, but but the edges just arent steep enough for the smaller UI. The eye is kind of squinting.

[noodle_snacks]

Disconnected the ground at the AV reciever end, no problems now. Are there any problems with doing this?

[mrshow4u]

highly recommended to land that receiver ground and isolate the signal ground through the use of the digital transformer. That way, if there's a lightning hit down your antenna, you'll have a better chance trying to route the heavens down the appropriate ground.

[noodle_snacks]

where can i get a digital transformer from?

I think you mis understood me slgithly, i disconnected the ground on the SP/DIF cable, not the mains safety ground. It started clicking on and off at random intervals the digital connection so i have re grounded it

[noodle_snacks]

oh, out of curiosuty, would using a decent sound card, instead of crappy onboard fix the issue?

[mrshow4u]

yes, you're right. I misunderstood. Okay, now floating the ground on the S/PDIF cable? Hmmmm, I don't like it. I think that digital transmission line should have return current coming back on the braid. There is a ground on your receiver in common with your computer (it sounds like), but it's a long way around for return currents. I'd still recommend the transformer. Transformers could most likely be found locally on junker DVD or CD players. I guess if it works, there's not a safety issue here, but there might be high error rates.

....It doesn't have too much to do with the "crappiness" of the soundcard, just whether or not they isolate. The "best" sound card with no isolation would cause a ground loop on your setup. The computer is grounded, the receiver is grounded, the S/PDIF line connects the different ground currents. You could try plugging the computer and the receiver into the same outlet.