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Thread: does using XLR cables instead of DMX cables screw up your lights? and how?

  1. #11
    XLR cable is higher guage and poorly suited for DMX... it just can't handle the data flow. A high quality XLR cable can transmit DMX up to 100 feet, but in most cases your range will top out at about 25 feet. DMX cable is good for almost 2000 feet. On the plus side, DMX is totally fine for audio. Because of this, I've stopped used XLR cable completely, actually. Easier to use one cable for both.

    I have a few terminators but have never found that they make any difference at all, even with runs/links over 1000 feet long. It's really odd that you are having issues with unterminated short runs.

  2. #12
    New Member
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    Oops, forgot to mention the terminator plug in my original response! At the time I placed the order for the dedicated dmx cable, I had also purchased a 2-pack terminator kit for a whopping $5. The may have been my cure all along and just forgot about it. Sorry

  3. #13
    Every XLR cable.. no matter what its price, or whether it's sold as an audio cable, DMX cable, AES/EBU (digital audio) cable.. etc.. has a "characteristic impedance", measured in ohms. This is NOT the resistance of the wire.. you cannot measure it with a simple meter.. and it doesn't change with the length of the cable. It's determined by the construction and materials used in the cable.

    If you have a name brand cable or one made with name-brand wire that you can identify, you can usually get this information from the manufacturer, it's on the spec sheets.

    According to some article I read a while back, audio cables range from around 45 ohms up to 150-200 ohms characteristic impedance. The 120 ohms required for DMX falls right near the middle there. So, yea, it is possible that one person can have GREAT results using audio cable for DMX, another can have very poor results, due to chance of having cables that happen to be near the correct impedance.

    The second factor is the quality of the DMX receiver in the fixture.. some are worse than others and more susceptible to the problems of incorrect cable or cable termination. Also not all transmitters are made equal, although this is less critical.

    The third factor is that: in pro fixtures, the DMX in and DMX out connections are simply wired together inside the fixture so the signal just passes through. The circuitry in the fixure only listens on the DMX line, it never transmits. The DMX cable is as if it were just one long cable.. which is how DMX is designed to work.. so that if one fixture loses power, the signal still passes through, everything else keeps working.

    But in DJ fixtures which have master/slave capability, often the DMX signal passes through the circuitry of the fixture and is repeated out again. This means that if the fixture loses power, everything further down the line loses signal. But it also means that instead of one long DMX line, you have many short ones.. and this reduces the affect of cable impedance and termination.

    Personally, I'd 1000% rather have a DMX setup where no fixtures repeated the signal, even if it meant having to use special cable and terminators.. because end of the day, you will have much less trouble and confusion when only one device (your controller) is responsible for the signal going to the lights.

    But anyway, hopefully this clears things up and explains why you will have some people who have great results using audio cables for DMX and some who have worse results. But whatever you do, use a terminator. They're cheap, and without one, you're just doing it wrong.

  4. #14
    Mic cables will work fine until they don't. It is based on the number of connections and total length of the cable runs. Another adding factor is the quality of the connectors.

    Data is meant to run on 120 Ohm cable, mic cable is generally around 80 Ohms.

    Using the right tool eliminates worries.
    BillESC
    Lighting, Sound & Video since 1973
    804-435-6858 [email][bill@entsyscorp.com]

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