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DMX cables

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Young Croc
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    Posted: 04 December 2017 at 2:52pm
I've got a noobie question that I couldn't find an answer to.

I've always just used microphone cables to link between 3 pin XLR lights. Is there any benefit to using proper DMX cabling (also 3 pin XLR). I was about to order some and the ones I looked at said they're 110ohms? Does this make a difference? Should I just order microphone cable instead?

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Post Options Post Options   Thanks (1) Thanks(1)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2017 at 4:06pm
It makes a big difference, Microphone cable will 'sometimes' work over short distances but can cause all sorts of problems over longer distances.

Audio is an analogue signal  that has a bandwidth that's normally up to about 20Khz, DMX is a digital signal that has a bit rate of 250,000 bits/per second (250Khz) , in theory a perfect square wave  has infinite bandwidth (Digital signals are or should be square waves), in practice this is not possible and the bandwidth is limited, even if the bandwidth is limited to say 10 times the fundamental the waveform will have been distorted and the signal degraded,  using the incorrect cable will distort the digital signal further and will eventually get to the point that the lights cannot reliably read the signal.
 
DMX cable should be 100-120ohms, anything else and you're asking for trouble!


Edited by APW - 04 December 2017 at 4:08pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2017 at 4:34pm
Unless you want to find one day its stobing or flickering or not doing what it's told dedicated dmx cables are required.

Mic cables might be a get out of jail free card if youre a cable short but you won't want to wire the whole rig with them.
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Meat Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2017 at 5:41pm
Thanks for the swift and definite answers. Duly ordered.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Posted: 04 December 2017 at 5:57pm
Truthfully, mic cable will work on smaller rigs a decent amount of the time. Certainly a good amount of the actual DMX cables you can buy are often marked up as mic cable on the sleeve.
If you already own a load of mic cable, then give it a go if its just for short runs for a few fixtures.
We've often run DMX down spare audio multi channels to avoid having to run extra cables in.

When I had my rig, I used exclusively DMX cable for everything, lighting control and any audio connections. Its absolutely fine using DMX for audio, not necessarily the other way around.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mk2_ginger_biscuit69 Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2017 at 1:24pm
Originally posted by norty303 norty303 wrote:

Truthfully, mic cable will work on smaller rigs a decent amount of the time. Certainly a good amount of the actual DMX cables you can buy are often marked up as mic cable on the sleeve.
If you already own a load of mic cable, then give it a go if its just for short runs for a few fixtures.
We've often run DMX down spare audio multi channels to avoid having to run extra cables in.

When I had my rig, I used exclusively DMX cable for everything, lighting control and any audio connections. Its absolutely fine using DMX for audio, not necessarily the other way around.



+1, i do exactly the same. All my XLR is made with blue sheaved cable too, just to make it clear and make it less likely to 'fall' into someone elses trunkEmbarrassed.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2017 at 8:34pm
If you use analogue/digital compatible audio cable (suitable for AES/EBU) it'll also be fine for DMX.
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