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XLR Or DMX?

Discussion in 'Lighting and Electrics' started by kadams17, May 3, 2009.

  1. kadams17

    kadams17 Member

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    Hi All -

    Another question...

    I was reading somewhere that it may be possible to link two intelligent lights using 3 pin XLR cable that is not DMX cable.

    So

    A.) What is the difference between XLR and DMX?
    B.) Can I link two movers with a basic XLR cable and then run DMX from instrument 1 to my lighting board? Or can I only use DMX?

    and if it helps, my movers have jacks for 3 pin and 5 pin. I would only want to link them using the XLR and run DMX to my board, and with the terminator in the last instrument.

    Thanks.
    Kevin
     
    Last edited: May 3, 2009
  2. BillESC

    BillESC Well-Known Member Premium Member

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    Mic cable is rated at 80 Ohms whereas DMX cable is 120 Ohms. In a pinch, mic cable can be used but is not recommended.
     
  3. kadams17

    kadams17 Member

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    Alright,

    I don't want to use the XLR cable, we might have an extra DMXer laying around but just in case I run out of cable, I want to have a somewhat backup plan.
     
  4. kadams17

    kadams17 Member

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    I guess I have another question.

    If I like the instruments together using a 3 pin DMX

    can i still make the run to my desk using a 5 pin?
     
  5. zac850

    zac850 Well-Known Member

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    DMX is a digital signal.
    XLR is a plug type that can have anywhere from three to seven (I think 7 is the most) pins.


    You can probably use a standard 3pin XLR cable to link the two movers together in a master/slave configuration; a set-up that is used by DJs so things just flash randomly to the music.

    5-pin, 3-pin, it really doesn't matter.
     
  6. icewolf08

    icewolf08 CBMod CB Mods

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    Yes, DMX signal is only transmitted on pins 1-3 of a 5-pin cable, this is why you can adapt from 5 to 3 and back at will.
     
  7. FatherMurphy

    FatherMurphy Active Member

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    If you're just doing short jumps from one mover to the next, microphone cables with three pin XLR connectors will often work ok, but it is a matter of luck, not design. DMX cable and mic cable are shielded differently, as well as the ohm rating BillESC mentioned, so the longer the cable used, the more likely you are to have interference problems. How acceptable that is varies with the show you're trying to do - if you're just looking for some constant flash and trash, random glitches won't be noticeable. If you're trying to do slow, delicate effects, you probably want to stick to the official DMX cable.
     
  8. Sayen

    Sayen Active Member

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    In a pinch it's definitely worth a shot. Our splitter failed once, so I had to run multiple DMX lines through the house. Short on cable we used an audio snake without any problems. Try to avoid it when you can, but it does work.
     
  9. lightman02

    lightman02 Active Member

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    Cat5 can be used as well in a pinch you would just have to solder the connectors on and it is legal but if not shielded you will have to make sure you isolate it from power cables.
     
  10. zac850

    zac850 Well-Known Member

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    Basically, the short answer is with data cable, if you need to try something, try it. The worst that will happen is it just won't work.


    I just want to re-state this (its a bit of a pet-peeve). DMX is a digital signal, while XLR is a type of plug. They are not interchangeable words. While DMX-cable usually refers to the specific Beldin cable with a 5-pin XLR plug at each end, DMX can also run over CAT-5, 3-pin XLR, mic cable, or other various cable/connector types.

    It is somewhat akin to referring to an extension cable as electricity.
     
    tcahall and (deleted member) like this.
  11. NickJones

    NickJones Active Member

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    Yes, you can do it, but like running video through audio XLR, it isn't advisable, I use it sometimes when focusing just to be able to use the console anywhere, but normal audio lead isn't meant to be used for data, and DMX is a data cable. You can get specially made 3 pin DMX with XLR connectors on it. DMX only uses pins 1-3, and the other 2 pins do nothing. (Does anyone know what they were intended for?) So the reason there are 3 pin connectors are for the 3 pin DMX leads, with XLR plugs on them, not really to be used with XLR.

    Some people insist it is fine, and they have no problems with it, in reality, they are just saying they haven't had any problems with it yet.

    Hope I cleared some stuff up.
    Nick
     
  12. lightman02

    lightman02 Active Member

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    Pins 4-5 were supposed to be used a secondary data, kinda like a reserve for future uses and expandability of DMX but was never really implamented. However DMX standard strickly states that DMX should be 5-pin only. However because only pins 1-3 are used, manufactures have found the 3-pin connectors are cheaper so alot of them use 3-pin instead of the proper 5-pin, and some give you bolth.
     
  13. KeeperoftheKeys

    KeeperoftheKeys Member

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    Devices that want to comply with DMX512-A (2004 or 2008 revisions) may not use XLR3 as connector. (They might be allowed to supply XLR3 connectors additionally to XLR5 I am not sure of that, but DMX512-A does not allow XLR3 any more).

    Also note that in proper DMX cables the data pairs should be twisted, on mic cables I don't know if that is the case.

    The second pair is defined as a signalling pair marked for future use. Chances are it will never be used officially because to many manufacturers use it for their own proprietary (talkback) protocols.
    However the most recent standard does strongly recommend fitting your system with both pairs so that you won't have to change all your cable infrastructure if and when they decide to officially use the second data pair.
     
  14. Chris15

    Chris15 CBMod CB Mods Premium Member

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    The DMX standards have NEVER allowed 3 pin XLR.

    Balanced cable will always be twisted pair. Note that some cheap cable is merely 2 core shielded; this is not balanced.

    I had believed that the DMX A standard did specify 3 or 4 ways of implementing return data and that at least some of those were reliant on pair 2. People have previously used it with relevant adapters to send 2 universes down the same cable.

    Given time, perhaps, RDM etc will take off and then we'll see increased use of pair 2. Now if only people could agree on a standardised method of running it over Ethernet then it would all play together nicely now... Don't worry, I think we're up to at least half a dozen audio over ethernet systems in reasonably common usage. :twisted:
     
  15. KeeperoftheKeys

    KeeperoftheKeys Member

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    True that DMX never specified the XLR3, but the language of the original standards left room for interpretations. DMX512-A does away with that in explicitly forbidding XLR3.

    RDM uses the first pair, the second pair is used for all kinds of things but non are standardised.

    Are they working towards making one standard in the sound world, or is there anyhow less movement like that because sound people usually use complete solutions?

    I also hope they will standardize DMX over ethernet soon, it will be great for the distribution of the signal, 'last mile' I think regular DMX is still better.

    Anyone know how far ESTA is with E1.31 (DMX over ACN)? It's no listed as published but also not in public review....
     
  16. Franklights

    Franklights Member

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    you want to use real DMX cable since it is the proper ohmage rating. You can use a 3 pin audio cable in a pinch but you may experience signal issues on runs over 10' to fixture. Definitely use a 120 ohm terminator as well. If the cable is the proper dmx data specification it doesn't matter if you use a 3 pin or 5 pin connector. That's why some lights have both.

    And I do have to agree on the pet peeve that a 3 pin or 5 pin XLR only refers to the connector, in the end it is the cable specification that defines it's purpose.
     
  17. MircleWorker

    MircleWorker Member

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    just another pet-peeve of mine, just like Lekos and now the kids say Source Four.
     
  18. NickJones

    NickJones Active Member

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    Yeah, but as the manufacturers still make there own DMX over Ethernet protocols, such as Strand's Shownet, ETC's Net3, ect, then chances are it will never happen.
    So theoretically I could run Mono audio feeds back up DMX to pins 4 & 5?
    Nick
     
  19. waynehoskins

    waynehoskins Active Member

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    Should be able to, sure.
     
  20. Chris15

    Chris15 CBMod CB Mods Premium Member

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    ... with a caveat. You will likely have noise induced on your audio line. DMX is running what +- 10 volts from memory (or was that 5?) and that will induce digital noise into the audio line. It will be more noticeable at mic level than line level...

    Also be wary of ground funkiness if the lighting and audio are not sharing Earths...
     

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