How can you get rid of coaxial spdif noise?

Question

I use a Denon DN1800F Dual deck CD player with the DNX800 digital mixer. When using the player coax out to the mixer's coax in I am getting some kind of electronic noise. This problem is not unique. I also get the same noise between other coax devices. I have tried changing cables, brands, etc.

Any suggestions on how to make a digital signal clean again?

Answer 1

The whole point about having digital audio is so that a high-bandwidth digital signal is used instead of analog audio, and the digital signal is impervious to noise, because any noise in the cable is cancelled out when the digital signal is decoded back to analog. The noise you describe is either being added to the audio signal AFTER the digital signal passes through to the mixer (so it's an internal mixer problem), or the noise is being added to the audio BEFORE it's encoded into the digital signal (so it's an internal problem with the CD player, or a bad CD). If there's too much noise in a digital line, the signal will usually just shut down until it gets synced back up - you hear this when talking on a cellphone in a bad reception area, the sound doesn't get noisy, it just gets full of gaps and then maybe quits altogether.

I'd say the next step is to send the CD player's signal to a different mixer, preferrably one that's known to be good (used for a long time by someone else). If the noise is still there, it's the CD. If there's no noise, it's the mixer.

My guess would be the mixer anyway - all signals in a CD player are digital, there should be no analog involved, unless it converts to analog and then BACK to digital SPDIF for some reason (which would be ridiculous).