DMX/Audio Cable

[JMeG]

Hi

 

Is it likely that our hire company have given us mic cable for a DMX line?

 

i.e. can you use mic cable for DMX signals?

 

I couldn't work out if there was a difference in the cable's resistance/shielding etc.

 

Please post SOON!

 

Cheers,

 

Jamie

[minimac]

fundamentally, no difference!!! but mic cables don't carry digital signals as well as specific DMX cables so it's advisable not to use them. having said that, we've got away with it on several occasions!! good luck!

[Djbarryblue]

yes it dose make a difference. you can use DMX for mic cable but its not recommended to use mic cable as DMX. How ever it has been done and sometimes get away with. there is a difference in the resistance between the two types of cable. this can some times cause your lights to flicker or you movers to jurk if you use mic cable.

 

Barry

[Stu]

I have used Mic cable before for DMX cable and seems to be not a problem for short runs.... I suppose it can depend on the quality of it etc but I've never had a problem on the times I've used them.

 

Stu

[chris512]

true DMX cable and mic cable have different resistance levels which make them good for specific purposes.

 

mic cable is fine for short 3 pin runs, but beware if the cable length is too long and/or you have no termination then signals can start reflecting down the line and your wobblies will do just that (by themselves)!

[RoyF18]

You'll get away with it for smallish stuff - everyone's done it and usually there isn't a problem. When you start having bigger DMX runs (and more fixtures) using mic cable and also not terminating then you'll possibly run into problems. (It's only happened to me a couple of times and they were both very big, complicated rigs).

[chris512]

there used to be (and possibly still is) a huge debate about this on the Martin LightJockey forum discussing if its good practice to always use DMX cable or if you get can away with mic.

 

the fact is yes you can get away with mic cable, but it all depends on the size of rig your using and the equipment. I had major problems with a rig which used about 80m worth of various different types of high quality mic cables and some cheap martin DMX thrown in with their macs (my advice salvage the ends and destroys the cables ASAP!) and with about 12 macs. As soon as we added the 13th B-) (how strange, SFX spooky music...GO) macs further down the line started doing their own thing and were suffering from data reflections.

 

we sorted this out by converting all our cable over to high quality Van Damme mic cable which seems to do the trick for the moment, but I still wouldn't like to trust using it on a big show just incase something happens when we expand.

 

in our new building there is a full 5 pin DMX infrastructure which uses 10 seperate buffered feeds so hopefully the problem won't crop up again!

 

 

to quote Paul Pelletier from Martin:

 

[talking about using mic cable instead of DMX] To me this is like if you should wear your seat belt while driving... you can get away with it for 20 years until...

[Ellis]

DMX 512 is implemented over the RS485 communications protocol. The cable is a transmission line. To get maximum power over larger distances, you need to be properly terminated and using a cable of correct characteristic impedance.

 

If you use mic leads, you will get losses. Eventually the losses will be too much and you will have problems.

 

If you do not terminate, you will get reflections. As the length varies, you will get nodes where the reflections cancel out the signal and devices do not work.