Topic: SPDIF grounding - electronics question

I'm trying to debug a problem with an SPDIF ground loop - The problem occurs when I plug in the SPDIF from the Out of my fireface UCX into an external SPDIF interface. I took a quick look inside the fireface and looks like both input and output SPDIF are transformer coupled, however, the coax on the output measures less than 1ohm to ground, which makes me think either the output SPDIF is not isolated in the way I expect or there is some error / solder bridge

Is it normal for the SPDIF out coax sleeve to be connected directly to ground? The 'in' coax sleeve is completely isolated. If anyone has a schematic of the SPDIF out section it would answer all my questions


Re: SPDIF grounding - electronics question

The SPDIF output is hard grounded because current regulations require this. SPDIF coax is an unbalanced cable, and the shield is not allowed to radiate high frequency signals.

If you are into soldering then put a small capacitor between ground and shield on one side of the cable, thus breaking the ground connection for lower frequencies, and plug that side into the receiving unit.

Matthias Carstens

Re: SPDIF grounding - electronics question

thanks, that's perfect!