How Do I Convert, Split and Merge DMX? What if I Do it Wrong?

If you’re using more than a few DMX fixtures, or have them spread out across your stage, you’re going to want to split your DMX signal!

And if you’re wiring up fixtures from different product lines, chances are you’ll need to convert connectors, signal type, and perhaps merge some DMX streams from different consoles!

Splitting, merging or converting DMX the wrong way can result in some really big problems, from fixtures dropping out to fixtures flickering, flashing, moving and doing all sorts of things that you don’t want to see during your show or service!

But do it right, and you’ll have a much easier show to set up with all of the functionality you desire!

If you are brand-new to DMX, check out this post explaining the basics of DMX before you read the post below!

Let’s start with converting DMX between 3 and 5-pin connectors.

Why Do I Need to Convert Between 3 pin and 5 pin?

If you’ve worked with a fair number of DMX devices, you’ll notice that some use 3-pin XLR jacks, some use 5-pin XLR jacks, and some use both to receive and then pass on the DMX signal.

So which is right?

The DMX protocol states that 5-pin is right, but then again, it only uses 3 of the pins.

In fact, many of the 5-pin cables commercially available are actually imposters- they only have 3 wires inside!  

Shocking, I know, but the fact is they extra 2 wires aren’t used, so why even have them?!?

In fact, any connector designed for low-voltage can be used.  

Some fixtures even have an Ethernet RJ-45 plug for DMX also, and that’s just there to confuse us further (Learn more about running DMX over “ethernet” cables here). Generally, these are fixtures designed for the install market.

Converting DMX

So that brings us to the actual conversion.  You may find yourself in a situation where you need to convert between 3-pin and 5-pin in order to wire up all of your fixtures.  There are 3 great ways to do this:

  1. You can use a fixture with both 3 and 5 pin XLR in/out jacks to do the conversion.  Just go 3-pin on the DMX in, and 5-pin on the DMX out or vice-versa, and you’ll be great.  The jacks are wired together.   Just don’t use this to split DMX, by using both connectors for output, or merge DMX using the input.  We’ll talk about all that further down the page.
  2. You can use a 3-to-5 pin adapter cable, such as this one, or this one, or both, if you’ve got to go back!  These are always a good little trick to have on hand, because you never know when you’re going to need one.
  3. You can use your opto-splitter if it has 3 and 5 pin outputs, like this one. Just don’t double up on the 3 and 5 pin of the same output if your splitter, if it has 3 and 5 pin plugs on each output.

It is cheapest and easiest to simply convert DMX using a fixture that has both 3 and 5-pin XLR’s.  Since that may not always be convenient, however, using adapters or a splitter can also work great and they’re great tools to have around if you work with a lot of lighting.

To recap – the plug you’re using doesn’t really matter, as long as it’s capable of passing DMX. As long as you’re using actual DMX signal, any DMX plug can be converted to another one with a simple cable adapter.

Splitting DMX

Splitting DMX is a whole different ball game.  You may sometimes find yourself in a situation where you need to split your signal, such as:

  • Having lights in all sorts of places.  It just makes it much easier sometimes to split instead of having to run cables for DMX in and out to all the far-reaching areas or your show!
  • Having more than 32 devices on one line.  The DMX standard only allows 32 devices per daisy chain of lights in order to preserve signal strength.
  • If you are going over 1800 feet in cable length.
  • For ease of wiring: We often split DMX to each lighting position just in case a fixture goes haywire or a cable gets tripped/snagged/unplugged, etc.  That way, a fault doesn’t take down more of the lighting rig than it has to!

Now that we’ve gone over the situations where you need to split DMX, let’s touch on how NOT to split DMX.

DMX cannot be split with a y-cable, because this is data we are working with, and that just doesn’t turn out well!  I’m hesitant to mention this, but, in a pinch, you can use a y-cable knowing that it severely degrades the signal strength of your DMX, especially if you make either of the “y’s” longer than a couple of inches.  So just don’t use a y-cable, it’s really not a good idea for your stress level!

A DMX Splitter is an essential part of a professional’s toolbox and is great for those of you just starting out too.  It is the proper way to split the DMX signal since we are working with data.

Think about it – you don’t make y-cables for your ethernet cables that connect you to the internet, or for a digital audio signal!

Sometimes called an Iso-Splitter, Opto-Splitter, Fleenor, or any other nickname made up by a production company,  these handy little boxes or rack mount units take the DMX signal in through their input, and split it out electronically by copying the data stream.  

Then, the splitter shoots the signal as a light beam of the signal across a small gap inside the unit – electrically isolating your signal.  

So, now we’ve got properly duplicated signal that is safe from electrical faults on other lines and has been amplified to full strength again.

If you have a lot of lights or are buying more and more fixtures that require a DMX input, an opto-splitter is a great investment that will both make your life easier and keep more hair on your head when it comes to troubleshooting!

A great model that I have had success with is the inexpensive ENTTEC D-Split, which is under $140 for 4 outputs of split data – 2 in 3 pin, and 2 in 5 pin.  Check out my full review of the D-Split here!

If you require a truss-mounted split, this unit by American DJ is also good, but only has 3 pin inputs and outputs, and is more expensive than the ENTTEC.

Merging DMX

Lastly, we hit the topic of DMX merging.  Though much less talked about than splitting, DMX merging allows you to use 2 consoles on the same lighting rig, or use 1 dimmer rack for 2 rooms with 2 consoles, or other strange scenarios like that.

Note that ETC dimmer racks and many others have 2 DMX inputs, so you don’t have to merge to accomplish this.  Check out your lighting system before purchasing a merger, and make sure you can’t do what you need to without a merger!

Merging DMX is not an overly common thing to do, and so I’ll keep this brief and to the point.  You can merge DMX with an active “box” just like splitting DMX, but it sure does not work to use a “y” cable!  Using a “y” cable to merge DMX will cause your data to interact in ways you didn’t know it could as it is combining at different points in the electrical phase.  It just gets ugly.  Don’t do it.  Ever.  Thanks!

Before we get too complicated, know this.  DMX merging is like DMX splitting, and you’re gonna need a special box to make it happen.  Since DMX merging is not nearly as common as splitting, there are a lot fewer products on the market, and they are more expensive.  But, if you need to merge, you need to merge.

This merger by Leviton is a good buy and merges DMX in a similar, but opposite way that a splitter splits.

Mergers have to choose internally what signal to use when there is a conflicting request, like both consoles bringing up the same channel at different levels.  The Leviton merger uses HTP, or highest takes precedence to determine this, but more expensive units let you choose between LTP and HTP.

Read more about HTP and LTP and how they work here.

Heading into the future, MOST merging is now happening via Art-Net or sACN – networked DMX signal. These signals can be merged by many output nodes or inside of lighting consoles.

Closing it all up

DMX splitting, converting and merging can either be a blessing or a nightmare.  

When done correctly, these 3 data manipulations can really make your life easier, solve problems, and help make your lighting system less prone to errors.  Done incorrectly, and you’ll have a world of trouble on your hands – hopefully, that’s not how you found this post!

Remember that even though DMX sometimes uses 3 pin cable, you can’t use a y-split like a microphone cable.  

Keep this in mind, and you’ll go far.  Happy splitting, merging and converting!

About the author