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MUlticore cabling vs cat5/6/7 cabling for analog audio

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MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby matkt051 » Mon Feb 18, 2019 6:03 pm

Hi all
I have a question with regards to sending bmic level audio signals over a multi core cable or CAT5/5e/6/7 cable

I have 8 mics that are currently hardwired into the A&H zed22fx mixer
These cables are getting damaged by the church folk walking over it. To solve this i suggested putting a snake to safely route and protect the cables

However I am at a cross road in selecting a regular multi core cable or using an RJ45 Ethernet cable to send 4 mic channels to the mixer
Can you please suggest or point me in the right direction ?
Currently the setup is partially permanent (where the mic cables would be removed and connected every week ) but this can be a permanent setup later on
The current distance between the mic and mixer is less than 20m but this could increase in a permanent setup

Many thanks
Mat
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby Hugh Robjohns » Mon Feb 18, 2019 6:22 pm

If you're likely to be upgrading the desk for a digital one in the next few years, a future-compatible digital-snake (connected over cat5 etc) might make good sense... but I suspect the most cost-effective and practical solution in your case would be a simple 8-way analogue snake and stage box.

H
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby Sam Spoons » Mon Feb 18, 2019 6:35 pm

I'm guessing you are thinking of using cat5/6 for an analogue snake? I believe it is usually ok for line level signals but probably not for mic level signals, and definitely not in an install that is de-rigged on a weekly basis. I'm sure Hugh will correct me if I'm wrong though. The problem with an 8 way analogue multicore is the size and cost of the cable. If you are running across access routes you need proper cable trunking, preferably bright coloured to reduce the trip hazard.
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby matkt051 » Mon Feb 18, 2019 6:45 pm

Hi
Thanks for the input

I was just googling and this came up
Seems like it worked

https://www.jeffgeerling.com/articles/a ... over-cat5e

What do you think?
Cheers Mat
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby Wonks » Mon Feb 18, 2019 6:49 pm

Remember that it's only 4 mic signals, so you don't need an 8-way snake (unless you want to build in future expansion capability).

An unscreened Cat 5e/6 etc. cable can at best cary two balanced mic signals as there is the ground wire requirement as well. But there would be a greater level of cross-talk and greater RFI pickup with the Cat cables than with mic cables or a multicore with individualy screened pairs.

Are there any hearing aid loops to consider, as they obviously radiate a lot of signal that can be picked up by poor mic leads and then cause feedback? If so, you really need to use good quality standard mic cable/multicore.
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby matkt051 » Mon Feb 18, 2019 6:54 pm

Hi wonks
Thnx for the reply
At the moment there are 8 mics in use
So my aim was to use two RJ45 ethercon connectors to send the signals to the mixer
I suppose from your post it seems like interference could be the main issue ?
Am I right ?
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby Mike Stranks » Mon Feb 18, 2019 8:28 pm

This might suit: https://www.vtx.co.uk/product.aspx?id=161

I've never bought anything from Vortex, but any queries I've sent them have always been promptly and helpfully answered.
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby Hugh Robjohns » Mon Feb 18, 2019 8:47 pm

matkt051 wrote:I was just googling and this came up
Seems like it worked ....What do you think?

Yes... But there's "it got us out of a hole" and "it works perfectly under all situations"!

I've managed to run both balanced analogue line level signals and digital AES3 down cat5e, but they're both much more robust than mic levels. I've no doubt you ~could~ get a mic signal down a cat5e cable, and I'm aware of some products that claim to make it workable... But a cat5e cable is designed to do a very different job to a purpose-made mic multicore. If that were not the case they wouldn't still bother to make analogue mic multicores! Although there's an overall screen, each of the pairs in a cat5e cable are (usually) unscreened, and rely on different twist (lay) lengths to try and minimise crosstalk between the very high frequency signals they're designed to carry. In contrast, a mic multicore uses identical lay lengths for each pair, but with individual pair screening (and sometimes an overall screen as well).

Interference from outside sources might not be too big a deal (as long as the cable doesnt get kinked or crushed), but it will be very reliant on the CMRR performance of the mic preamps, which varies considerably between different designs. However, my biggest concern would be for crosstalk between the different pairs in a cat5e cable, especially since you easily could find yourself with one 'quiet source' mic signal at -60dBu running for 20m alongside another (eg kick drum mic) pushing 0dBu, so crosstalk could be very assymetric and could potentially be boosted by 50-70dB. I've seen reports of crosstalk better than 90dB at 20kHz etc, but when you could have 60dB difference between signals in the first place, and 60dB of gain being applied, that doesn't fill me with huge confidence.

As for the application described in that article, they only passed two mic signals down each cat5e cable, not four, and they paralleled two pairs per channel -- although I'm not sure what affect that would have on crosstalk.

So while I can see the financial attractiveness of using a couple of cat5e cables, and it might be persuaded to work in some situations, I personally wouldn't take that route. A proper 8-way mic multicore just isn't that expensive or unwieldy to rig, and is a known, proven, robust and reliable solution which is readily available.
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby wireman » Mon Feb 18, 2019 9:56 pm

It is implicit in some of the replies here but various arrangements of shielding are available for these cables.
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby jaminem » Wed Feb 20, 2019 12:27 pm

Hi There, you may want to check Ward Beck out if you are considering audio over cat 5/6/7

http://ward-beck.com/all.html?brand=36
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Re: MUlticore cabling vs cat5/6/7 cabling for analog audio

Postby ef37a » Wed Feb 20, 2019 1:37 pm

I would say give is a try. But use shielded CAT cable if running mics.

I have my bungalow kitted out in the stuff (came free!) and I have put mics one end and the cable run must be >30mtrs up and down the loft and through a passive patch panel. There was no hum pickup.

Crosstalk could be an issue but the twists are very tight, far tighter than any mic cable and are staggered so the adjacent pair does lay precisely aligned with the others. The shielded version has a common drain wire and I found no problems with phantom power for 4 mics outlets, although I only had 3 phantom powered mics to test at the time.
I guess if you had an SM7b on a kid and sent a kick down the same 4 pr there would be some crosstalk but for your application would XT at -30dB at 10kHz really be a problem?

A standard 13A double steel back box can have a blank punched for 4 XLRs and even the "backbone" solid pairs cable is remarkably rugged, cheap too! Or you can use flexible cored patch cable but it is rather more expensive. You could make up 2 by 4 XLR boxes for very little outlay and just drop in the spare when one is trashed then re wire it.

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