Why do you have to use the DMX terminator?

A DMX terminator is an important part of any DMX DJ light system. If you find the DJ light switch off, flicker, change color, pattern, etc. That may be a sign that you need a DMX terminator!

When no DMX terminator is used, the signal, when arriving at the end of the DMX chain, will bounce back or “reflect” into the cable. This is called “reflections”. Not the entire signal is reflected, only a small part of it, but that’s enough to deteriorate the signal. The information carried in the signal is therefore not clear as it should be and your lights start to behave strangely. Just picture this : your appliance receives the reflected signal as well as the original signal, it sees two numbers at once. Therefore it gets confused. It is a simplification, but helps to understand what is happening. A DMX terminator will simply stop this reflection from happening, keeping the single signal clean.

A DMX chain Sketch for DMX lighting systems

The load impedance don’t match 110 ohm and this causes possible reflection of DMX signal bouncing forward and backward on the cable. One common mistake is to use microphone cables, namely microphone cables, instead of DMX cables. Indeed balanced microphone cables have the same plugs or connectors, but they have a different cable impedance. Therefore, though you can plug it and seems to work, these cables are different and should not be used. Microphone cables have a lower impedance than DMX ones, this characteristics will dampen the square signal which will affect the readings of your fixtures. Using a Microphone cable is a common mistake, so be careful!

DMX signal through Microphone cable

You need a DMX terminator if the sum of your AES/EBU DMX cables is longer than 590 feet throughout your chain. Below that, having one is recommended but not mandatory. Therefore, if you are a mobile DJ with not many lights and thus do not plug many DMX cables, then not having a terminator may be fine. If you do have a problem on short cables, that may be caused by a combination of issues : reflections + low quality cables + bad light fixture. In that case a DMX terminator will probably solve the issue by removing the noises in the signal, wherever they come from.The higher the cable length or number of appliances, the higher are the chances of having trouble. So do not hesitate to put a DMX terminator when you increase the complexity of your installation. If your DMX cable length was only 20 feet long and you did not use a DMX terminator.

DMX signal through DMX cable

Please note that when having a problem, it may happen that only one appliance behave strangely. That may happen even when you placed the exact same model at several places in your chain. That tends to confuse people into thinking that the DJ light is faulty when really it was only a DMX terminator missing. The reason behind is that noises may be added throughout the chain by the other lights and slowly accumulates, light after light. Eventually the first lights were not affected but at one point of the chain, it starts to affect one specific appliance. It may also be just because one of your light is a bit more sensitive or a combination of the two phenomena. But then again, using a DMX terminator will solve the problem. So just buy one, its cheap anyway!

AES3-2003 over CAT-5 data cable works well, and the standard recommends it. CAT-5, CAT-5e, CAT-6, CAT-6e and CAT-7 RJ45 data cables have 100Ω characteristic impedance and support runs significantly longer than 100 meters without additional equalization or amplification. RJ-45 connectors are recommended, so the full range of structured wiring components are available for AES3-2003 use. For any future facility upgrade, it’s worthwhile to consider using structured data cabling systems and abandoning all conventional audio cabling. Also, you can save a lot in time and equipment by simply reusing any existing data-networking cable.

Any terminator will do as long as it has the right number of pins and a 120 ohms resistor. This 3 pins DMX terminator or this 5 pins DMX terminator version, available on suteer web page, they are perfect for the job!

3-PIN 110 ohm DMX TERMINATOR black DMX3M002                                         5-Pin 110 ohm DMX TERMINATOR DMX5M002