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Topic:
Shielded digital coaxial cable
This thread has 23 replies. Displaying posts 16 through 24.
Post 16 made on Tuesday October 23, 2018 at 20:51
Ernie Gilman
Yes, That Ernie!
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On October 23, 2018 at 16:58, davidcasemore said...
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.

This needs a bit more info. Standard CABLE COMPANY DROP CABLE is steel core. Those of us who are aware of this fact ditched that kind of cable for satellite and TV antenna use years ago. We carefully never buy CCS, which is short for "copper-clad steel."

As far as whether a variety of RG6 is "the best," I don't think so. If you buy compression RCA plugs, then yes, the shielding ability of RG6 Quad is of benefit. But if you use F connectors of any sort and then go through an F to RCA adaptor, you introduce two points of failure into your cable. Failure is likely due to simple atmospheric corrosion of the contact between the center conductor and the adaptor.

It's also not the best because it's rather stiff. It's also not the best because it's overkill. I once discussed this with the guy from Belden who wrote the low voltage installation guide. When I posed the question as to the benefits of Quad over foil plus braid, he agreed that the only place this might be necessary would be, for instance, in a building directly below or adjacent to a TV transmitting tower.

There's only one real advantage to using quad: the next installer who looks at the installation can't fool the customer (and himself) by saying "wow, looks like the last guy didn't use the best wire. Quad has gotta be better because it has twice the shielding! We gotta replace this stuff!"

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.

This should give you excellent results.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 17 made on Tuesday October 23, 2018 at 23:16
Brad Humphrey
Super Member
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Everything in the same rack being feed from the same power conditioner and only a 2M cable.
I am 99.9% sure it is not EMI.

It still could be a ground loop. Is there a coax coming in for video service? If so, disconnect that from the rack temporarily to see if the noise goes away.

Impaqt seems to have experience with a problem that was very similar. And it is an easy check to do what he is suggesting. Might want to go with that idea 1st.
Post 18 made on Wednesday October 24, 2018 at 01:38
Ernie Gilman
Yes, That Ernie!
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On October 23, 2018 at 19:24, Impaqt said...
You really should check if it works without 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.

THIS kind of off-the-wall bizarro problem makes a whole lot more sense than magically appearing EMI or ground problems.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 19 made on Wednesday October 24, 2018 at 06:58
james_aa
Long Time Member
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Ive just gone to site, seen the issue first hand and fixed the issue. The issue was that in the AVR zone (see below) there was a "static" sound over the audio.

Im not sure "why" its fixed by doing this but this is what i did :

The audio system is built like this : Autonomics MSM2a (streaming sources) --> Audio Control Director M6800 (Power Amp, Matrix, Pre Out (for AVR zone)) --> AVR Yamaha RXA670

There are 7 distributed audio zones powered by the M6800, and one surround sound / distributed audio zone powered by the AVR which gets a pre out from the M6800.

The M6800 has 2x digi coax pro outs, i was using output A and putting that into the AVR. I swapped the wiring so that we now use output B into the AVR, using the same cable and everything else. So the only thing that changed was the output.

This seems to have fixed this issue, but i have no idea why. Any ideas ?
Post 20 made on Wednesday October 24, 2018 at 07:21
buzz
Super Member
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I'm assuming that this is a copper connection. There could be or may have been a mechanical issue with the cable contact that created or broke a ground loop. Possibly, the cable dress had been too close to a noise source and you accidentally now have a better route. Far fetched but possible: There is a current path crossing the two output jacks and jack B is closer to zero potential.
Post 21 made on Wednesday October 24, 2018 at 09:29
highfigh
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On October 24, 2018 at 06:58, james_aa said...
Ive just gone to site, seen the issue first hand and fixed the issue. The issue was that in the AVR zone (see below) there was a "static" sound over the audio.

Im not sure "why" its fixed by doing this but this is what i did :

The audio system is built like this : Autonomics MSM2a (streaming sources) --> Audio Control Director M6800 (Power Amp, Matrix, Pre Out (for AVR zone)) --> AVR Yamaha RXA670

There are 7 distributed audio zones powered by the M6800, and one surround sound / distributed audio zone powered by the AVR which gets a pre out from the M6800.

The M6800 has 2x digi coax pro outs, i was using output A and putting that into the AVR. I swapped the wiring so that we now use output B into the AVR, using the same cable and everything else. So the only thing that changed was the output.

This seems to have fixed this issue, but i have no idea why. Any ideas ?

Did you notice the audio level from both outputs? Is it equal when using both, meaning, can you adjust the output level?
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
OP | Post 22 made on Wednesday October 24, 2018 at 13:00
james_aa
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On October 24, 2018 at 09:29, highfigh said...
Did you notice the audio level from both outputs? Is it equal when using both, meaning, can you adjust the output level?

There is no volume control in the web GUI for the M6800. So i dont think the output can be adjusted, we just feed it into the AVR and let the AVR control the volume for that zone. The M6800 controls the volume for all its powered zones though.
Post 23 made on Wednesday October 24, 2018 at 13:02
Lowhz
Senior Member
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April 2012
1,168
Static "around" the music usually means PCM word clock sync is drifting and he's hearing digital hash.
Post 24 made on Wednesday October 24, 2018 at 14:53
Ernie Gilman
Yes, That Ernie!
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On October 24, 2018 at 06:58, james_aa said...
The M6800 has 2x digi coax pro outs, i was using output A and putting that into the AVR. I swapped

"Swapped means "exchanged," implying using both A and B outputs. Did you? Where did Output B go?
the wiring so that we now use output B into the AVR, using the same cable and everything else. So the only thing that changed was the output.

That is, Output A is noisy. Anybody have any ideas why that might be?
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
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