CAT5 to XLR?

[Jeremiah Rickert]

I was trying to lighten my load a bit when it came to cables, and someone suggested to me that I could use CAT5 network cable between two CAT5 to XLR adapters instead of rolling a 100' snake down the aisle of an auditorium that I do a lot of shooting at.

Has anyone ever tried this? He said the setup he saw was basically a 4 XLR snake, but with CAT5 in the middle.

[Seth Bloombaum]

I haven't had direct experience with this, but you'll find a wealth of products and discussions if you search google on "XLR balun".

A few years ago I considered purchase. For the specific run we frequently had to make in a large convention center room I ended up making up a 4-pair XLR snake using cable from Redco. Something like a 325' run. Note that premium cable is needed as you start to get over 250' or so, and this may not be the best approach for hi fidelity needs for music. We were putting a couple podium mics and a return to amps on it - spoken word only. Works great. I did put a good preamp on the podium end, so it was all line-level.

2 and 4-pair XLR snakes are quite handy for a bunch of uses. I was using a 100' 2-pair for a stereo audience mic just last week... I bought an 8-pair x 30' a few years ago; never used it.

[Paul R Johnson]

They work fine, but you do need to buy cable made to be used this way. We run digital audio now, via cat5, and you need cable you can coil on a drum. proper cat5 kinks and bends and doesn't lay flat. It is also too stiff. The cable we use for our digital kit has a much tougher outer cable, and lays and rolls properly.

[Greg Miller]

I've never tried this, but I'm curious and would love to hear some actual experiences.

The thought of running mic level without any shield really worries me. And if you extract four audio pairs from the CAT5, then there would be no "return" conductor(s) for phantom powering. It might be passable for line level, depending on the nearby noise sources. After all, TELCO has been doing this (at lower than line level) with all our copper talk pairs for over 100 years; but the telephone earpiece rejects the LF hum and harmonics from induced power line noise.

[Richard Crowley]

Remember:
1) If you use all four pairs for audio, then you will have no ground reference. That may work fine for line level or for conventional dynamic microphones. But it will not work with condenser mics or anything else (like active direct box) that needs ground for phantom power return.
A possible way around this is to use SHIELDED Cat5 cable and use the outer shield as the common ground return for all four pair. Or, if you need less than the full 4 pair, you could use one of the pair as the ground connection (XLR pin 1)
2) Of course if you use common UTP (UNSHIELDED twisted pair), the pairs are not shielded, so they will be much more suspectible to ambient garbage getting into the line. You could expect this to be more of a problem with mic-level signals, and somewhat less with line-level.
3) The input circuit at the end of the wire should be TRUE BALANCED in order to take full advantage of the differential signal through the pair. If the input is UNBALANCED, you are almost guaranteed problems quite possibly bad enough to be unworkable.

[Brian P. Reynolds]

Cat5 cable works fine if you do it right.....
Firstly use Cat5e cable which has tighter specs then 'standard Cat5' cable...... 'e' is the thing to go for. Cat6 and Cat6e are better again.
https://en.wikipedia.org/wiki/Category_5_cable
http://pctechgo.hubpages.com/hub/Bas...network-cables

I have made 'breakout' cables (RJ45 plug to 3x XLR-M) and (RJ45 plug to 3x XLR-F), I have about 3-4 sets in my OB kit , as well as 3 drums of Cat5e cable (180m) (160m) and (150m) which were left over from several install jobs.
Just use RJ45 joiners to attach the breakout cables to the drums of cables.
I have made them as 3 core / pair cables with the 4th core /pair being the 'earth' connection for ALL of the 3 cores to enable phantom powering.

I have used them on many occasions in many different ways, firstly as mic level cables on cross country horse events where great cable lengths are required. I have run 2x Sennheiser 816p mics + 416p mic on (180m) Cat5e cable joining then to 100m conventional analogue multicore snake then to the TV OB Truck. So a total of 280+m of cable per mic at mic level with phantom power...... NO buzz or humm (but it was outdoors in a lightly wooded forest) I found no need to use battery powered mic-line amps.

I have used them as a loom to go to court side mics (416's) of a Basket Ball match, this time cores 1 & 2 had mics on them and the 3rd core had Data to control POV Qball cameras. Again NO buzz or humm

Another time was for a UHF 2Way Duplex radio system, core 1 TX, core 2 RX, this was to get the UHF system indoors in a stadium for better usage rather than trying to push through brick / metal walls at quite a distance from the usage area.

So is Cat5e useable?........ Very much YES....... BUT get good at re-terminating RJ45 connectors as they are quite fragile with rough usage (so regard them as to be replaced every 2nd or 3rd job)
Keep the cable on drums and not hand wound.

[Paul R Johnson]

As for hum - don;t forget that for many years broadcast studios sent their output to transmitter sites over ordinary twisted pair - telephone systems don't use shields.

Useful UK forum topic here
Audio Over CAT 5 - Blue Room technical forum

[Richard Crowley]

Originally Posted by Paul R Johnson

As for hum - don;t forget that for many years broadcast studios sent their output to transmitter sites over ordinary twisted pair - telephone systems don't use shields.

Yes, but that was back in the "good old days" when line-level was actually 600 ohms and proper transformers were used for source outputs and destination input ports.
Here in the "modern era", there are lots of solid-state "shortcuts", some of which are not nearly as robust or impervious as those old-school designs.

[Don Palomaki]

Two thoughts to consider. Typical CAT5 is not anywhere as rugged as typical snakes. The trade off is weight for long life and relative audience foot resistance.

In the more recent good old days a 45 dB S/N ratio was good, 1% distortion was acceptable, and frequency response was limited, and TV was all SD (NTSC or PAL). Before that it was all AM radio and B&W TV. An before that ...

[Steven Digges]

I have been down this road with disastrous results. It was video signals we were running not audio. The standard cable used to transmit a video signal from source to a projector in our live shows is 5 wire RGB. Think of it as 5 BNC cables in a single sheath. One cable for red, green, blue and a horizontal and a vertical sync cable. It is very heavy and difficult to deal with when you have long runs, often terminating at a projector rigged to truss high over the audience.

In recent years many reputable manufacturers have come out with small lightweight converter boxes to transmit a video signal over cat 5 cable. It sounded to good to be true, it is. At first everyone got excited over the thought of replacing all of that heavy 5 wire cable with something as easy to run as cat 5 or cat 6 cable. It is being done by some AV companies but not on shows when I am the technical director.

The bottom line for me is it is just flat out not robust enough to hold up to live show work. Weak plastic connectors, light unshielded cable, converter boxes on each end. It all proved to be a recipe for disaster. Just too much that can and will go wrong. Especially when rigged through truss full of Lecos and projectors that are accessible only with a man lift. No thank you! It proved to be a very poor replacement for good old heavy five wire cable!

Kind Regards,

Steve

[Greg Miller]

Originally Posted by Richard Crowley

Yes, but that was back in the "good old days" when line-level was actually 600 ohms and proper transformers were used for source outputs and destination input ports.

Those old Western Electric line-level transformers were excellent. In fact, they were used to step down the studio impedance of 600 ohms to 150 ohms on the leased TELCO pair. That resulted in more across-the-board signal loss due to the DC resistance of the pair, but less HF rolloff due to distributed capacitance of the pair. Of course the impedance was stepped back up to 600 ohms at the transmitter end (where a passive tuned EQ was used to get the response reasonably flat).

Even though we were feeding +8 dBm into the line, the level at the transmitter end was significantly lower. And in really quiet parts of the program, you could still hear occasional clicks from the pulse dials that shared the multi-pair cable with the program pairs.

Come to think of it, a lot of radio stations used unshielded small-gauge twisted pair to interconnect the different studios within a given premises. But that was all transformer balanced at a nominal zero VU (give or take a few dB). Electrically speaking, CAT5 isn't all that different, but the comments about grounding, shielding, and flimsy connectors are all valid; and using solid conductor CAT5 for portable wiring where stranded is more appropriate, is asking for trouble.

[Greg Bellotte]

So meet my "DT-4" adapter. Have made several sets of these. I would only use these for balanced line level sources, but in this context they work great! We use them quite regularly at broadcast remotes, to get an intercom port over to the RF truck, or PGM audio to uplink or distribution point. Our cat5 cables are all "patch cord" variety (stranded) up to 250ft. I would NEVER try to run mic levels down this setup, but properly used it is quite handy.

[Seth Bloombaum]

Note that the commercial XLR balun products include a transformer.

Balun = Balanced/unbalanced.

Not too sure of what the design is in this context - lower impedance? Conversion to/from balanced?

In any event, it appears to be more than an adapter.