DMX on XLR

[TupeloTechie]

Is it possible to run a dmx signal through a hardwired xlr, so I don't have to buy a 300ft DMX cable to control two wiggly-mirrors...

[icewolf08]

Possible, yes. Good idea, no. DMX is a form of data cable, more similar to a Cat5 ethernet cable than it is to standard XLR for sound. Standard XLR is a different impedance and wire gauge than DMX cable. If your run was 10 feet, it may not be a big deal, but over a 300 foot run you are probably looking at substantial data degradation. Let me say it one more time, it is not a good idea to run DMX on standard XLR mic cable.

You can, however, buy DMX grade 3 conductor cable that is slightly cheaper than 5 conductor, but at about $0.44/ft for regular DMX cable it is pretty cheap to buy in bulk and cut to the length you need. Check out http://www.systemstore.com and look for the Gepco DLC224 DMX512 data cable. I just bought a roll (1000 feet) at $0.44 and it works great. (especially since the Belden equivalent is up to something like $0.75/ft)

[soundlight]

You can also use CAT5 networking cable for DMX. This can be done, it has been tested and is up to spec to handle DMX. So, if you have an ethernet run, you should be fine as well. If not, get DMX cable. It's not worth losing the data during a show. We use mic cable for lengths up to 50 feet, but I wouldn't trust it for more than that, even with a terminator. Wrong resistance.

[Brilliant2007]

Would not do it...well, not usually! What type of fixture are we talking about here? Are we talking install/semi-installed or one week for a production?

Even with Cat5, you still have to convert it on each end.


DMX cable is super cheap to rent! Even if you don't have anyone close, you could have it shipped to you via UPS or FedEx. Infact, the shipping would be more expensive than the cable.

[TupeloTechie]

we are just running two cheap mirror scanners, I believe they are made by chauvet, I am pretty sure they are not that good, as the guy who bought them said he only paid about 100 a piece for them, but my teacher said that we should use them, so I have to hook them up.

[icewolf08]

If your run is more than 50 feet and you are starting with very low end units you really need to use real DMX cable. And if your teacher is the one who wants to use them, then tell him that in order to use them you need the correct cable. DMX cable really isn't that expensive.

[TupeloTechie]

we do have lots of cat5 though, how do you wire it for dmx?

[len]

I've run data down audio snakes hundreds of times and used mic cable many other times with no issues.

HERE COMES THE CAVEAT: But I have a splitter on the chain, and I'm also getting power from the same leg as the lights. But when something goes wrong, it's usually with improper cable. So you can probably take your chances using what you have already, but when it goes south that should be your first place to look. I certainly wouldn't spend money on proper shielded, twisted pair when the cost will likely be more than the lights. But if you can rent some, do that. Assuming that the run of this show is such that it makes sense to do so.

[Van]

If you run it through cat5 ethernet be sure that the run is point a to point b. It cannot be running through a switch, router, or any other node, except a dmx opto-couple. We used to install Vista Architectural control systems with Cat5 all the time when I worked for RoscoET.

Just another note, Don't run DMX on a snake, or any other XLR / mic cable. It will make a crappy fixture perform even crappier. There are simply too many variables in the way of accomplishing your intended goal.

[Andy_Leviss]

Okay, time to be a bit of a pedant. Not only can you run DMX on XLR, but you do every single time you use it in most any application.

XLR is NOT a type of cable, it's a type of connector. DMX by spec is on 5-pin XLR connectors, while it sometimes is implemented with 3-pin. Audio signals also use 3-pin XLR, on what's often called microphone or audio cable, a particular type of shielded twisted-pair (STP) cable.

What you mean to ask, I presume, is "can you run DMX down audio cable," and as others have posted, the answer is that you can, and it may work, depending on circumstances and even a bit of luck, but you shouldn't. There are very specific characteristics of digital-grade cable that typical audio cable doesn't meet, and as noted, it can degrade the signal.

It's one of those where if it works, great, but if it doesn't (and it might at first, but then stop later on), there's nothing you can do to fix it.

You can, for example, run analog audio down digital grade cable, but the reverse is not a good idea. It's sort of a square vs. rectangle thing, y'know? This is why a lot of installs today are spec'ing digital cabling for all audio lines, so that if later on somebody needs to run AES/EBU or another digital audio signal down it, the proper cable's already in place. A bit more expensive, but cheaper than having to re-install cable later!