we believe we are getting EMI on a digital coaxial cable.

Dose anyone know of a good shielded digital coaxial cable ?

Quad Sheild RG6.

Do you know if anyone makes a pre made patch cable version ?

How do you know that it is EMI?
What is the observed symptom?
What is the source?

@bret

- i believe it’s emi due to the fact the source (autonomicns mms2a) has 2 outputs 1 optical, 1 digital coax and it’s only happening on the digi coax

- the observed symptom is stuttering / pops on the playback

- autonomic mms2a

What hard drive you you have connected via USB?

I’ve got a 1tb portable hd attached. (Not a flash drive)

I would remove it and test without it plugged in.

I want to throw a monkey wrench into the works to open up the possibilities you might consider.


It would be equally valid to ask



I suppose a ground loop might cause that. I'm not at all sure.

Can you define the problem even further? For instance...
What if you're using the best possible wire right now? That is, please tell us what you're using.

Is this a new installation and it always did this? Is it an old installation? Has something about the system changed recently?

A personal tale:
I use a wireless keyboard. If I plug the keyboard dongle into the front of my computer and run a USB cable to an outboard HDD from the adjacent USB socket, the keyboard sometimes doesn't register key touches. If I connect the dongle further from the HDD plug, all works well.

Thanks Ernie

It’s not a new installation c. 10 months old. We had this problem at install and to solve it i purchased the a sheilded digi coax that could get delivered same day on amazon prime, so I could complete the job.

Installed the cable and problem solved, but 10 months later it seems to be back again, although i can’t rule it out being a different issue with similar symptoms.

Standard Quad Shield RG-6 is typically made with a copper-clad steel center conductor. Which is exactly what you don't want for S/PDIF.

You need a high-quality digital audio cable. There are dozens of manufacturers of pre-made, pre-terminated cables like these. If you need a long run then I would go with a high quality cable such as Belden 1694A and terminate it with a high-quality connector from Belden or Canare.

I would be willing to bet it is NOT a problem with the cable picking up EMI. It would be an extremely rare bird for something like that to happen.

The questions:

What kind of coax is ran now? You call it a 'digital coax', what is it's construction? Most 'digital coax' from manufactures are solid copper center, with a 80% or better braid. LWC I use is over 90% braid w/foil.

How long of a run is the coax? And what does the coax run near?

You are using optical & coax digital, which would indicate you have 2 separate systems using the outputs. Info on this?

As Ernie suggested: Since you are having issues on the copper connection and not the optical, strong chance it is ground related (depending on the answers to the above).

Thanks brad

- I believe it’s a Fisual brand digi coax cable, will get some more specs on it tomorrow

- the run is 2m, it runs in the rack from the Autonomics MMS2a to the Audio Control director M6800 matrix amp

- we are using optical and digi coax as the MMS2a has 2 streams built in, but one is digi coax and the other optical, they both go to the m6800

-The rack is powered by a surgex 1230 into via an Aten pdu, then to the devices

If it is a ground issue how could I confirm it / resolve it ?

You really should check if it works withough the hard drive plugged in. I've had the same issue on 2 MMS3e's. Pulled the seagate USB drive off, and it went away. theres some polling of the hard drive in the new firmware that doesnt play nice with some drives.

If you disconnect the coax and just us the optical that would confirm and/or resolve the ground issue as the optical would have no conductive path to ground.

I bet it's a hard drive problem, not the cable.