It is a common perception that audio cables can be substituted for DMX cables when setting up your lighting gear. They appear similar because they both have three-pin XLR connections. However, the actual cables and DMX signal, are designed different and transmit the signal differently. A DMX signal is digital and audio signal is analogue.
The 3 Pin connectors are the same, but the cables are very different. The audio cable is designed for audio frequencies (low frequencies) and is a low impedance cable. DMX data cable is designed for a wide bandwidth high frequency data stream, it is higher impedance. Using DMX specific 3 pin XLR cables with all your 3 Pin DMX devices will result in maximum system performance and reliability, and at show time that is the bottom line.
On the surface, both cables look the same. However what differentiate them is the electrical properties of the wire. When sound is sent down the wire, it doesn’t get sent as ones and zeros exactly, the method of communication is based on the voltage going up and down. But when sending a digital signal it is sent using ones and zeros. Therefore they should not be used interchangeably.
Brief History of DMX:
The DMX standard cable was designed with 5-pin XLR cable as the connection for data. This was done to distinguish the cables from audio XLR and to leave the last 2 pins open for “future expansion”.
Back in the 90s lighting companies realized that they could use 3-Pin XLR for DMX because the DMX Standard only used 3 pins out of the 5 pin cable that it specified for lighting control. Many of the 5-pin cables on the market only have 3 conductors inside as the last 2 pins are not live. Some DMX fixtures have 3-pin alongside the 5-pin, and some only have 3-pin DMX jacks.
Which is better?
This leaves you with 2 choices – use the cheaper audio XLR cables to run your lights or buy a 3-pin DMX cable that looks very similar to your audio cable. It is easy to accidentally plug in the wrong cable and get unexpected results.
Audio cables do work for DMX lighting, but they are not guaranteed to work perfectly, problems can and will probably arise when you least expect it. You may encounter problems such as flickering, loss of signal, interference and strobing. This is because audio cables are lower impedance (ohms) and therefore don’t make a good cable for digital signals. In comparison DMX cables are designed and built for digital signals and are support a much higher bandwidth and frequency. A cable that meet the DMX required specification must be 120 ohm cable.
A DMX cable is a shielded, three-pin XLR cable that transmits data signals between lighting fixtures ensuring a solid, consistent signal. These cables are generally thinner so they can easily wrap around tight corners, fit in small spaces and taped inconspicuously to the floor. The shielding on a DMX cable is generally better because it’s transporting data, as opposed to audio cables, which are transporting sound signals.
Be sure to choose 3-pin or 5-pin depending on the fixtures you own! Do keep in mind that if a fixtures has both 3 and 5 pin plugs, you may go “DMX In” 3-pin and “DMX Out” 5-pin or vice versa. However you can’t use these plugs as a splitter.