Hi all

I've been searching around for a solution to a problem.

In all my theatre setups, I always end up with 3 hanging mics or 3 shotguns on each lighting bar, and therefore always end up with 3 XLR's running down from each one. This makes life less tidy and also eats up XLR's when you're working from a high bar. In the past I've just taken my smaller 8 channel multicore and sat it on a walkway in the grid, and cabled out from that, but I'm now looking for some individual cables that can carry 3 mic channels. Ideally the cable would be only slightly thicker than standard XLR cable.

I'd toyed with using cat5 cable and commoning the ground's together (as they all go back to the same mixer, where they will be commoned anyway) but am not quite sure what implications this has on phantom power. I'd be using stranded cat5 "patch cable", which leaves me with a pair left, either to use as a spare channel, or to tie together and use for the ground along with the drain wire/foil braid around the whole lot.

The ideal soloution would be for a 3 pair cable with each pair individually screened, but I can't seem to find any.

I don't want to start looking down the small channel count multicore option, as I think that will start to be a little heavy (it certainly has been with my 8 channel one in the past!).

I reckon to have looked in the cpc catalogue, as well as some other suppliers I use for the day job, and cant find anything quite right.

Anybody been here before?
Can I use cat5 and common the grounds? The cable will always be used by me for this specific purpose, and will always go back to the same mixer.

How about Canford's MSJ series? 3 pairs with an outside diameter of 5.6mm.

That's the fella!!!!

Thank you very much, for some reason Canford had never crossed my mind!

I'd still be quite interested to see whether people think the cat5 option is do-able.

Using CatV you'd want to use STP (shielded) rather than UTP at the very least. I'd still be surprised if you didn't run in to cross talk issues, especially over a long run, as each individual pair in a multicore is generally shielded. You'd also need to do a lot of tedious heatshrinking or have a termination box at each end to break out from the STP nicely.

The CAT 5 solution will work reasonably well once you have dealt with the detail of breaking out into individual pairs. A small box with 3 XLR sockets at the top end with or without a multiway connector and a multiway direct into tails or stage box at the other end. Crosstalk is not an issue as the pairs are twisted and the three mics will have similar signal levels give or take 10dB or so. Interference from lighting should be minimal if you can avoid close coupling, again due to the tight twist of CAT 5. Screened version is obviously preferable though not essential. The highest risk is probably instability due to the common phantom, dependent on your microphone types, and mechanical damage as CAT 5 is nowhere near as rugged as a decent mic cable. I have used foil screened data type cables of 2 to 6 pairs for stage fanouts for many years without any problems but would not consider them for situations where they were regularly moved.
Brian

In my "get out of jail" box I've got a couple of standard "electrical" backboxes - the sort of thing that would be used for a single 13 socket etc - fitted with a plate with 4 XLR-type cutouts. In the cutouts, I've got 3 XLR sockets (2M1F on one, 2F1M on the other) and a single CAT5 socket. Grounds commoned.

Works fine - I've used it over about 100m, in a very electrically-noisy environment (adjacent to lift motors and an Orange transmitter) - however this for line-level signals, and no phantom.

I've just built a breakout box and a 100m Ethercon terminated reel of Cat5 to do something similar - take a look here for a couple of pics of the finished article.

My thoughts with the phantom was that in effect I'm just building a multicore without the stage box, and I've seen multi's before that have had all the grounds connected together (via the casing of the stage box), so thought it woud not really be too different.

I already have a cat5 line level distribution setup similair to how people have described above, however it was the added complication of mic level and phantom that was concerning me. I have lots of cat5 already, so it seems the way to go, at least for a trial, though I may well look at the dedicated cable as it will be a bit more rugged and is the right tool for the job.

British Telecom seem to do ok for crosstalk on what is basically the same layout of cable (twisted pair in a common shield) although their audio is at line level.

Cheers for the advice.

C

If you use Cat 6 STP cable, according to wikipedia, then each pair is individually shielded. Obviously the ethernet RJ45 connector can't deal with this, but if you did some mega heatshrink/hellermann reinforcement, then you could break straight out to 4 XLRs? Also thomann do a 4 pr multicore cable here for £1.83 per M and VDC do something similar.

Matt

How about a 7-pin XLR at each end of the Cat5 cable?
The breakouts for the mic / console / stagebox final connections would then be 7-pin XLRs to 3 standard 3-pin XLRs (via your favourite type of mic cable). This idea eliminates the need for cleverly engineered heat-shrunk breakouts of the Cat5 and the inherent problems of maintaining and creating screening of individual CAT5 pairs.

The 7-pin XLR need not necessarily be the only solution - there are a number of multipin circular connectors that are smaller and neater than the trusty XLR. If money is no object, then the Lemo UK sales office would be a good starting point.

The crosstalk issue will probably be a non-issue as the "lay length" of the Cat 5 pairs is different; this is a crosstalk-reducing feature of the Cat5 design.

Use the 4th pair as an extra couple of grounds instead of leaving it redundant or clipping it short.
Using shielded Cat5 patch cable gives you stranded cores.
If ruggedness is a factor, you could consider something like Kelsey's "Duracat", which is a stranded, shielded Cat5 cable encased within a very rugged sheath. Excellent for studio installation as well!

Regards,

Gareth.

I've got a 190 foot six pair multicore which doesn't have each pair screened, but just has a overall screen. I've got the overall screen connected to channel 1 ground at each end.

I normally use it as a returns snake, but when pressed into service as a mic snake it works fine, with no noticable crosstalk.

On this basis, I think Cat5 would probably work acceptably well.

Great stuff, I'll have an experiment and report back.

Cheers all

I made myself a cheap multicore using some 25 core overall screened cable. To check the crosstalk I fed the output of a synth at full volume into one channel (muted) and cranked the gain up on all the other channels leaving the inputs open circuit. I could just about hear the synth above the noise. I suspect that if you keep all the signals at roughly the same level you won't have a problem with crosstalk.

I've heard of quite a few people using Cat5 for mic cables with no problems although I've not tried it myself.

Cheers

James.