How to tell DMX XLR from Audio XLR?

Dale, Welcome to the forums. here is a good video on you tube that helps explain most of your questions. check it out.
http://www.youtube.com/watch?v=n4f7WxnMa0Q
Sincerely,

I've got you beat. I'm also an audio production company and until recently, I was running DMX down my 56-channel audio whip, which is a 200-foot cable terminated with MASS connectors. Break out of that into my stage box, then run up to another 200-feet of XLR microphone cabling to various dimmer packs and other DMX fixtures, but of course, I did the good thing and terminated it with a DMX terminator.

DMX cabling is intended for usage for 110-120 ohms, which is a recommended loading for DATA applications. It has to do with the impedence of the wiring. XLR cabling is designed more for 600-100 ohms. I will guarantee you that you'll hear a difference if you put a mic on a DMX cable, in the concept of "squashy" and "rolled off" especially in the highs. It ain't pretty. Just the fact that both DMX and XLR are shielded twisted pair doesn't make it 100 interchangable.

DMX and XLR cabling both use twisted pair. But what else uses twisted pair? Why, Cat 3, 5, 5e, 6, 6e and other brands of telco cabling, with the exception of most flat 2 and 4 wire modulate telephone cables.

Heck, if you want, you CAN run ethernet over barbed wire. Not that I'd recommend that, but if you can do that(and I HAVE done that, as a test), why not do the same with yor mics and lighting? I mean, look at the time you'd save telling people to stop screwing with your cabling?

You bring up a poin taht I've been trying to make. We have too many cabling standards. This in and of itself is not a bad thing. I mean, look at what we can do with XLR. I've got a 2-pin XLR cable that is some sort of power cable. I have 4-pin XLR cables that I use for power for many of my video devices. I of course mainly use 3-pin for microphones. This is where things get all wierd. From what I hear, DMX was originally using a 5 pin connector, which was silly because DMX only uses TX- and TX- with a shield, so it only needs three wires/pins to operate, which is why DMX is moving to 3-wire cabling: to save money. This is also why 3 to 5 wire DMX converters aren't really that big of a deal, all the money is tied into the connectors anyways.

Let's take a deeper look.

Yes, what you're doing works. Why change? Well, if you're a sound production company, isn't reliability a concern?

Is the color of the cable a concern? Oh please. What, if it's black is all equal? No. there are HUGE differences in audio cabling and it tends to mostly be black too. And yes, I CAN hear it, but it becomes an issue mainly in A-B comparisons. But DMX cabling will say it's for data applications or DMX, where as most microphone cable will say it is for microphones. It says so right on the black outer jacket. It has to, mainly so people don't get confused, especially when they are in a pile of cables and are making cables.

The signal in DMX is streaming, so it has some tolerance in the protocol. It also runs HOTTER than audio, which is also why the impedence is significantly lower. It's a matter of signal optimization. You want to load that cable properly.

Just this year I've converted over to AccuCable for my lighting, and my lighting isn't anything amazing. I've made a 200-foot primary cable, and then 3 25-footers and 6 3-footers. Well, whatever they are, it ate up a 300-foot spool of Accucable. What I've noticed is that things appear ot work faster, be more reliable and more responsive, especially when using MyDMX and my DMX Operator. And yes, that's not a whole lot of DMX cabling. At my last show, I had to integrate some mic cable into my DMX cabling to make it all work. This is an ongoing issue that I am working on and will continue to address for a bit.

Are you going to damage anything by using XLR cabling? No. Well, maybe but if that happens, it's going to be part of a larger catastrophic issue anyways and not due to "operator error or negligence". Worse case is that your stuff won't work as well.

Any production company that I know uses the proper cabling for the job. Or, at least any respectable one. In my sound production company, lighting has become a bigger and bigger issue. It now makes sense to move to the proper cabling. Talking to about 50 lighting companies in the past 4 years, ALL of them are using DMX cabling for their DMX cables, not one of them uses microphone cables. But I guess when you spend a few million bucks on gear, you can afford to spend some money on proper cablng, right? In the end, DMX cabling isn't that much more expensive than mic cabling.

As far as a DMX terminator, this is a data signal. Since we're dealing with an async signal with no clearly defined end, we need a terminator to prevent signal reflection and bring the signal chain to an end. Remember SCSI terminators?

You can make your own DMX terminator by using a male XLR and a 120-ohm 1/4-watt 5% resistor. Should cost you a couple of bucks for 100 resistors and maybe $4 for an XLR connector. I have made 3 of them. Solder the resistor between pins 2 and 3, polarity doesn't matter.

I'm not here to sell you anything. I'm not here to say "Hey, Accucable is your only option". What I am saying is that I've been pleased since moving my DMX off my audio snake and onto dedicated DMX cabling.

Step up to DMX cables. You'll be glad to you did. Worse case is in a pinch you can grab XLR's as needed.

I beleive I have ordered another 300-feet of pre-made Accucable. It is an ADJ product and it appears to be rather rugged and durable.

As far as your state of shock, your manuals all say to use DMX cabling. DMX fixtures, controllers, software, they all say to use DMX cabling. Where is the shock coming from?

Now, go get some DMX cable, build yourself a few DMX terminators. Do it right, your business deserves it, and so do your paying customers.

quote:

As far as your state of shock, your manuals all say to use DMX cabling. DMX fixtures, controllers, software, they all say to use DMX cabling. Where is the shock coming from?

Well, I should clarify that I am not a professional sound or lighting engineer. I am merely the IT / network administrator / "Technical Services Admin" for a small rural K-12 public school district.


The audio and lighting systems were mostly put together in the late 1990's by someone who cut corners every which way, and didn't really care about safety or the details, as long as stuff just WORKED.

I've never seen anyone open a breaker panel to attach wires directly to the bottom of the circuit breaker bus bars, because not enough current was available from wall outlets to run the show. Also I think it's perhaps just a bit unsafe to use BUSS screw-in fuses in lamp sockets on stage as ignitors / puff-pots for pyrotechnics.

But he is no longer available to "help", and so I am slowly following behind peeling off all the duct tape, replacing all the crushed and battered old XLR connectors with Neutrik, and trying to get the hiss out of the sound system.

I probably should have expected to discover something like this has been going on with the DMX gear.

- Dale

Hey, I'm an IT guy by day. And I don't cut corners there either. But that's just me. I'm lazy. I work my rear off hard to get the job done right so I can move on to the next project. Case and point, I designed a network so well that in 12 years, it's never needed a service call and the company that I deployed and installed it for has refused to take it down, prefering it over cost-savings solutions via VPN because it's been that reliable. The dial-backups have NEVER been used, but have been tested.

And anyone stupid enough to attach bare wires to buss bars is, well, going to want to be caught on video camera because that's some good YouTube stuff. That can safely be done, but that high current needs to go through additional transformers and/or breakers for safety.

Oh please don't tell me you're seeing them using fuses inline to sockets for flash pots and puffs.... man, if a fire marshall came in, that place would be shut down fast!

But I could also troubleshoot your sound system. Just not right now. I carry my own. Where is your hsis coming from? Old mixer? FX(common, use a gate). You do have to keep in mind that horn loaded speakers are going to hiss, it's just the nature of it. The issue is "is this just background stuff or is this being sent out at a rather noticable volume level?". I mean, I've run from crap to top of the line(I'm at top of the lne) and I can hear it, it's a fact of life. But, all his is NOT equall. Yeah, it's barely there, you're OK. But you've got to troubleshoot each and every single component and cable anyways, so you're going to be having a ton of fun.

You've got your work ahead of you, that's for sure. You've also got the right idea of simply doing it right. You can cut corners by using generic connectors and maybe not top of the line cabling. You don't need a Lexicon PCM96, when a MPX500 will work jus fine. I may knock my old Mackie 1604VLZ ever since getting an Allen & Heath ML 5000 48B mixing console, but I tell you what, with that older Mackie, I've run circles around many an engineer, even today.

Making it work is one thing. Making it work right and be safe is entirely different. I have an entirely mobile sound and lighting company(we're adding video too). We come in where there is nothng but power, load it in and make it all happen. Safe, proper. Every time. If I don't feel it's safe, I won't let others near it. I'm the boss, I take the risks, not the talent, not my crew, and I want them all safe or it's a no go. I've only ever had one issue and that was with a stage panel I felt was too loose, but I made sure it was not going to fail before I let my crew start setting gear on it.

If you need help, you can contact me via my web site, which is running again. Not 100%, but it's like 99%(my banner ad CGI needs to be redone). Or phone if you want. I've had many calls from readers of this forum. If I'm not busy, I'm happy to help.

Take your time, do it right. Cabling is cheap. I can help you get Neutrik ends cheap too, because you'll need a lot. When you do need the Accucable, I can point you to dealers as well. Get the Acculink ends as well. I love Neutrik ends though, but I use Neutrik for audio, Acculink for DMX. I must admit, I use Neutrik ends for my DMX terminators! Readily available and I get them for super cheap at my local dealers.

I've pretty much taken over management of the school's music/drama department's audio and lighting equipment, since nobody else seems to really have an interest in learning the technology after that other guy went away.

At this point I've gotten most of the audio system hiss out, by eliminating their huge pile of balanced to unbalanced adapters they were using for no reason. Why use six 25 ft adapter cords in a spaghetti bundle, to go from the wireless mic receiver to the sound board 3 ft away? I eliminated all that mess and put in six new XLR 3-ft cords from receiver to board this summer.



Their Peavey amplified speakers hiss loudly at 10 in a quiet room, but 5 is silent so I have them using that now, and it's more than enough audio output for the school's stage/gymnasium.

Their now 10yr old Peavey 2002-16RQ only has unbalanced outputs, going to unbalanced inputs on the Peavey EQ, and I get a major hiss increase JUST from plugging the sound board into the powered speakers, with all channels down. I know that sound board really should be replaced with something that has XLR outputs.




But this is "minor stuff" that all has to wait, while I figure out what to do with their six 700mhz Audio-Technica Unipak receivers which may have to be replaced due to the Feb 2009 analog TV switch-off and conversion of the 700mhz band into a commercial wireless network.

I'm hoping Audio Technica finds a way to get a white spaces rule variance from the FCC, so we (and thousands of other people) don't have to suddenly replace all these wireless systems.


As such this DMX data cable situation isn't very high on my list of expensive problems to fix, at the moment. Those receivers alone will eat most of their equipment budget.

- Dale

I know this ain't a marketplace, but contact me offline about selling those AT units if they are in decent shape. I love the 1400's, I have a pair and I'm beefing up my inventory. I know the 700MHZ band is supposd to be offlimits, but it will be years before those get sucked away. Heck, I'm even beefing up my VHF inventory

If you want some good cost effective replacements with some diversity and functionality with multiple channels, I'd recommend then 2000-series.

The 1400-series is SO DEAD, AT won't even re-crystal them. They'll do an 1100-series for $35, but won't touch the 1400 series because of the frequency range. Believe me when I say that there are thousands of angry sound companies and DJ's out there.

I could go on for hours about wireless stuff, but Shure is taking the bull by the horns on behalf of all companies. It ain't going well, but thanks to Shure, the Congress has at least their chin (of their head) out of their butt.

Why the speakers are hissing is an issue. could be te amp, could be the pre-amp, could be the horns.

But, you're right, you shold replace it with something that has BALANCED outputs, XLR isn't necessary. My Mackie 1604VLZ has balanced 1/4" outputs. Balanced is the key, but I think it is deeper than taht with that console. The EBTech Hum Eliminator will balance an unbalanced connection, and they've worked nicely for me for their intended purposes which is to safely lift/break grounding issues. 1/4" in and out, balanced/unbalanced, works both ways. Will make/break balanced connections and cost around $65 for a 2-channel unit that is about the size of a direct box.

Horn loaded speakers SHOULD hiss a tiny little bit, it's the nature of the beast, but it shouldn't be super noticable. Check your gain settings, put it in the middle.

Sorry for the late response. You can hit me at my web site if you need more realtime help. I'm slammed right now but I'll break for you.