DMX vs AUDIO cables

[sunray]

I've seen and heard all sorts of arguments about using the right cables for DMX but today I stumbled into the opposite while setting up for a show.

The official tech guy has insisted that only his cables are used, for 2 reasons:

1) There will be no issues identifying his and others at de-rig,

2) They are 'good quality' cables.

 

So I picked up a couple of cables with blue marking rings on the XLR's (DMX) to use for the intercom and was told they would not work for audio and in no uncertain terms how stupid I am for trying to use DMX cable incorrectly, I asked what the problem is and a long lecture followed about how DMX runs pin 3 hot vs pin 2 for audio, even to the point where plugs were opened to show where the red wire is.

It didn't help matters when I saw the poor workmanship and asked if the plugs were terminated by a monkey, another lecture about how he has been making cables for 10 years, my 50 years worth was oh so irrelevant...

 

Good god I didn't have to edit the CR's back in...

[Stuart91]

I don't think the electrons care what colour of insulation is around them.

 

Most of the pre-made DMX cables that I come across have the red core on pin 2 anyway.

[mackerr]

I've seen and heard all sorts of arguments about using the right cables for DMX but today I stumbled into the opposite while setting up for a show.

The official tech guy has insisted that only his cables are used, for 2 reasons:

1) There will be no issues identifying his and others at de-rig,

2) They are 'good quality' cables.

 

So I picked up a couple of cables with blue marking rings on the XLR's (DMX) to use for the intercom and was told they would not work for audio and in no uncertain terms how stupid I am for trying to use DMX cable incorrectly, I asked what the problem is and a long lecture followed about how DMX runs pin 3 hot vs pin 2 for audio, even to the point where plugs were opened to show where the red wire is.

It didn't help matters when I saw the poor workmanship and asked if the plugs were terminated by a monkey, another lecture about how he has been making cables for 10 years, my 50 years worth was oh so irrelevant...

 

Good god I didn't have to edit the CR's back in...

 

DMX cables are not only good for audio, they're good for digital audio, which regular mic cable is not. Regular mic cable is not recommended for DMX or digital audio, both of which require 110Ω cable. Analog balanced audio has no specific impedance requirements and pretty much any balance cable will work.

 

Mac

[Jivemaster]

We'eve all heard of the experiment sending digital audio down wet string once demonstrated (at PLASA?). BUT once the cable lengths increase the right cable is essential and the rule of thumb is that failure bites at the most critical time in the most expensive show on the most critical cable run.

 

Yes I knew a DJ who satisfactorily fanned DMX out radially in bell wire at the top of a t-bar stand, he got away with it for years but it was a really short length.

[paulears]

Surely the only issue with colours is that they're connected to the same pin each end. It's not like house wiring where brown hurts and blue usually doesn't?

 

This person you met is in the position off setting rules and being ignorant. He wins, even though wrong. No point attempting to change the mind of these people. I used to when young. Now I just go along with them, and smile - and don't give them lectures they don't want to hear. It's taken me over 50 years to realise that resistance really is futile with folk like this.

[Brian]

My response in such situations...."I could agree with you but then we'd both be wrong."

[Mickstup]

I'm doing a small show and want to use some DMX controlled effects on stage and the official tech has said he has a spare line in his audio snake I can use, it will be about 50m long will there be any issues. TIA.

[johnhuson]

So I picked up a couple of cables with blue marking rings on the XLR's (DMX) to use for the intercom and was told they would not work for audio and in no uncertain terms how stupid I am for trying to use DMX cable incorrectly.

 

On the basis of which I presume they were 3-pin XLR cables, in which case you could point him in the direction of the DMX standards which stipulate 5-pin connectors should be used?

[timsabre]

I'm doing a small show and want to use some DMX controlled effects on stage and the official tech has said he has a spare line in his audio snake I can use, it will be about 50m long will there be any issues. TIA.

No, it will work fine. The only problem you might have is if there are any mic channels in the same cable with the gain cranked really really high, you can sometimes hear the DMX then.

[Stuart91]

I'm doing a small show and want to use some DMX controlled effects on stage and the official tech has said he has a spare line in his audio snake I can use, it will be about 50m long will there be any issues. TIA.

 

You'd do yourself no harm to have a DMX terminator on hand, which you can plug into the last light in the chain. A terminator can sometimes prevent flickering on long lines.

 

A terminator is nothing more than a resistor put across the two signal cores, usually soldered into an XLR plug. You can make some up yourself if you're that way inclined, but they're readily available on eBay and Amazon too. (Or you can just scrounge one from any passing lampy, they usually have one in their pocket) :P

[sunray]

Most of the pre-made DMX cables that I come across have the red core on pin 2 anyway.

Indeed

 

DMX cables are not only good for audio, they're good for digital audio, which regular mic cable is not. Regular mic cable is not recommended for DMX or digital audio, both of which require 110Ω cable. Analog balanced audio has no specific impedance requirements and pretty much any balance cable will work.

Agreed, but Beldon 9500 style cable should be 110Ω which is what the DMX spec was written around and is used for most installed tielines.

[Mickstup]

I'm doing a small show and want to use some DMX controlled effects on stage and the official tech has said he has a spare line in his audio snake I can use, it will be about 50m long will there be any issues. TIA.

No, it will work fine. The only problem you might have is if there are any mic channels in the same cable with the gain cranked really really high, you can sometimes hear the DMX then.

 

 

 

I'm doing a small show and want to use some DMX controlled effects on stage and the official tech has said he has a spare line in his audio snake I can use, it will be about 50m long will there be any issues. TIA.

 

You'd do yourself no harm to have a DMX terminator on hand, which you can plug into the last light in the chain. A terminator can sometimes prevent flickering on long lines.

 

A terminator is nothing more than a resistor put across the two signal cores, usually soldered into an XLR plug. You can make some up yourself if you're that way inclined, but they're readily available on eBay and Amazon too. (Or you can just scrounge one from any passing lampy, they usually have one in their pocket) :P

 

Thanks for the replys, I have a terminator already, it should save threading a DMX cable round all the seating if its ok to use his audio. Cheers.

[sunray]

Yes I knew a DJ who satisfactorily fanned DMX out radially in bell wire at the top of a t-bar stand, he got away with it for years but it was a really short length.

I installed some dimmers in a nightclub and we promptly got blamed for significant flickering problems on the LED pars, the original DMX installation was 13x13 PAR's, the 'main' DMX line ran along one side with choc bloc joins to provide the feed to the first PAR in every line. It worked perfectly until we added the new dimmers and incandescent fittings which were not even a part of the DMX set-up.

 

Surely the only issue with colours is that they're connected to the same pin each end. It's not like house wiring where brown hurts and blue usually doesn't?

This person you met is in the position off setting rules and being ignorant. He wins, even though wrong. No point attempting to change the mind of these people. I used to when young. Now I just go along with them, and smile - and don't give them lectures they don't want to hear. It's taken me over 50 years to realise that resistance really is futile with folk like this.

What he didn't know is I had already used some DMX cables elsewhere...

He is part of the shows crew and one of the scenery guys had already tipped me off that this guy removes the cables very quickly after the final show and will/does remove everything, especially cables that do not belong to him.

No I don't try to offer advice to people like him, I learnt that one a long time ago.

 

On the basis of which I presume they were 3-pin XLR cables, in which case you could point him in the direction of the DMX standards which stipulate 5-pin connectors should be used?

That's a difficult one when every single fitting in the system has 3pin connectors.

 

No, it will work fine. The only problem you might have is if there are any mic channels in the same cable with the gain cranked really really high, you can sometimes hear the DMX then.

I have always been concerned about this but in practice I've only found it to be a problem if something is not right, such as no terminator or some audio running unbalanced.

[DrV]

The great thing about using an audio tie line to get DMX down to the stage is that you can use a dynamic mic (someone else's) as a signal tracer ☺ Edited February 12, 2019 by DrV

[Andrew C]

It will work fine - unless it doesn't.