In this guide: The short answer · Daisy-chain limits · What a splitter does · Opto-isolation · RDM · Outputs, connectors and format · Merging two desks · Comparison table · Which one for which job · Popular picks · FAQ

A single DMX line is fine for a handful of fixtures sitting in a row. It stops being fine when the rig spreads out, when the fixture count climbs, or when one faulty lamp or cable keeps taking the whole show down. That is the job of a DMX splitter, also sold as a buffer, booster, repeater or distributor.

This guide covers splitters only. Addressing, universes and cable are in DMX explained, plugs and terminators in DMX adaptors and terminators, and going cable-free in wireless DMX.

The short answer

• Use a splitter when a single run would exceed the device limit, when the rig branches in several directions, or when you want a fault on one run to stay on that run.
• Each splitter output is a fresh DMX line with its own device budget and needs its own terminator at the far end.
• Buy an opto-isolated splitter for touring and mixed rigs. Isolation helps stop an electrical fault on one leg reaching the desk or the other legs.
• If you address or monitor fixtures with RDM, the splitter must say it supports RDM. Many basic splitters do not list it, so check before you buy.
• For one universe and a handful of runs on a truss, something like the ADJ Data Distro 6 is a tidy option. For a dimmer rack or tour rack, a 1U unit such as the ChamSys GeNetix GD10 or Elumen8 Cygnus SPLIT6 suits better.

Why a daisy chain runs out

DMX512 (ANSI E1.11) borrows its electrical layer from RS-485, and RS-485 counts load in unit loads. ENTTEC’s support notes put it plainly: you can connect a maximum of 32 unit loads to one DMX line, because RS-485 specifies 32 unit loads per line segment.

A unit load is not quite the same as a fixture. ENTTEC points out that many modern receiver chips are rated at 1/2, 1/4 or 1/8 of a unit load, which would allow more fixtures, but most fixture datasheets do not state the figure. Assuming one unit load per fixture is the safe planning rule.

Splitter makers give similar working guidance. Elumen8’s manuals for its Cygnus splitters say each output can feed up to 32 fixtures per signal line, with up to 100m of total cable length.

Fixture count is not the only reason to split. A rig that fans out to several trusses or stage positions is usually easier and tidier to cable as a star from a splitter than as one long chain that doubles back on itself.

What a splitter actually does

A DMX splitter is an active device: ENTTEC describes it as decoding the incoming signal and retransmitting a freshly regenerated copy on each output through its own RS-485 driver. Every output becomes a new segment with a fresh 32 unit load budget, its own terminator and full signal strength.

So every output run needs a terminator on its last fixture, as covered in the terminators guide. The splitter’s own input is a different matter: most units have a thru or link socket and a termination switch, so you can either carry the input line on to another device or terminate it at the splitter. The Data Distro 6, Cygnus SPLIT6 and D4 Branch RM all have one.

The thru socket is often not a buffered output. Chauvet notes that on the Chauvet DJ Data Stream 4, the four outputs are isolated from each other with the exception of the DMX thru, and ADJ describes the ADJ D4 Branch RM loop output as passive. Treat thru as a continuation of the input line, not as an extra split.

Splitters do not add universes. One input universe goes out of every output (or two universes on dual-input units, below). To get more universes from a desk you need more desk outputs, or Art-Net/sACN nodes.

Opto-isolation: what it buys you

On an opto-isolated splitter the input and outputs are not electrically connected; the data crosses an optical coupler. A wiring fault, a damaged fixture or a mains fault on one leg has a much harder time reaching the desk or the other legs.

Theatrixx states the input and each output of its xVision 1:8 DMX splitter/isolator are optically isolated up to 1kV, so line failures are contained and do not take down the whole network. QTX describes its DMX-D4 as making it quick to diagnose and fix faulty fixtures without the whole system failing.

Isolation is not all-or-nothing, so read the wording:

• Each output isolated from the input and from each other. Elumen8’s Cygnus splitters and Transcension’s S8 and RS6 are described this way. This is the most complete arrangement.
• Isolated in groups. The QTX DMX-D4’s four outputs are opto-isolated in pairs: outputs 1 and 2, and outputs 3 and 4.
• Buffered, isolation not stated. Prolight describes Transcension’s CS2 and HS2 as having an independent driver on each output without claiming isolation. ChamSys does not list opto-isolation for the GD4IP or GD4D, while it does for the GD10. Where a maker does not state isolation, do not assume it.

RDM: does the splitter pass it?

Remote Device Management (ANSI E1.20) lets a desk or tool address and query fixtures over the DMX cable. That means data travels back from the fixture to the controller, so a splitter in the path has to handle two-way traffic. ADJ, for example, describes the Data Distro 6’s DMX + RDM mode as allowing bi-directional communication, and Theatrixx says its splitters forward RDM data to each port.

If you use RDM, only buy a splitter whose maker lists RDM support. Of the ones we sell, these say they do:

• ADJ Data Distro 6: a switch selects DMX512 only or DMX + RDM.
• ChamSys GeNetix GD10, GD4IP and GD4D: RDM E1.20 compliant, with an RDM disable button that strips RDM and retimes the DMX output.
• Theatrixx xVision 1:8 and the xVision 1:3 reversible module: RDM forwarded to each port, plus a switchable Timing Safe Mode that bypasses RDM.
• Elumen8 Cygnus SPLIT8PRO and Cygnus SPLIT2: both list RDM.
• Nicolaudie Architectural NASPLIT-4: RDM compatible, according to Nicolaudie.

The makers of the ADJ D4 Branch RM (specified as DMX512 1990 compliant), Chauvet DJ Data Stream 4, Elumen8 SPLIT6 and SPLIT10, QTX DMX-D4 and the Transcension units do not list RDM support. That does not prove a unit will block RDM, but it is not something you can plan on, so check with the manufacturer before relying on RDM through one of them.

Why the disable button? Some older fixtures do not get on with RDM traffic. Theatrixx says its Timing Safe Mode bypasses RDM and boosts DMX signal quality to ensure compatibility with older-generation fixtures, and calls it a handy troubleshooting feature. ChamSys’s RDM disable button likewise strips out RDM data and retimes the DMX signal.

Outputs, connectors and format

How many outputs

Count your runs, not your fixtures, then add one or two spare. Four to six outputs suit a band or small venue rig; eight to ten suit a dimmer rack, tour rack or a stage with several trusses and floor positions. Two-output units like the Cygnus SPLIT2, Transcension CS2 and HS2 are for splitting a line in one specific place, such as each side of a stage.

One input or two

The GD10 can run as 1 in to 10 out or as 2 in to 5 out, so one box can split two universes. The Cygnus SPLIT10 and SPLIT8PRO take A and B inputs with a toggle on each output to choose which one it carries.

3-pin or 5-pin

Choose by what your fixtures use, and see the adaptors guide for converting. Some splitters fit both on every port: the D4 Branch RM, Data Stream 4 and Cygnus SPLIT6. Others are 5-pin only: the Data Distro 6, GD10, SPLIT10 and SPLIT8PRO, and the XLR5 Theatrixx models we list (Theatrixx also makes 3-pin versions). The QTX DMX-D4 and Transcension CS2 are 3-pin, and the HS2 is 5-pin.

Rack, truss or install

• 1U 19-inch rack: D4 Branch RM, Data Stream 4, GD10, Cygnus SPLIT6, SPLIT10, SPLIT8PRO, Theatrixx xVision 1:8 and Transcension RS6. Best in a dimmer or control rack.
• On the truss: the Data Distro 6 sits over a standard 50mm truss tube with hook-and-loop straps or an M10 clamp point. The GD10 has M12 clamp fixing; the Cygnus rack units have an M10 point.
• Mobile box: the Transcension S8 is a compact steel unit with holes for truss clamps or wall mounting.
• Outdoors: the GD4IP is IP65 rated with Seetronic IP65 connectors.
• Installs: the GD4D is DIN-rail mounted with Phoenix screw terminals and runs from an external 12 to 48V supply; Nicolaudie lists the NASPLIT-4 as a 12 to 48V DC unit.

Power

Most rack and truss splitters take mains. A few also have a mains link output, which tidies cabling on a stand or truss: the Cygnus rack units have Power Twist TR1 in and out, the Theatrixx xVision 1:8 has powerCON with loop thru, the Transcension CS2 has IEC in and out, and the Transcension HS2 has a powerCON input and two powerCON outputs. The GD10 and GD4IP have a powerCON TRUE1 mains input; ChamSys does not list a power output on either. Check the maker’s limits for any power link-through, and remember that designing, installing and testing electrical systems is a job for a competent person.

Merging two desks

A splitter takes one signal out to many places. A merger does the reverse: it combines two controllers into one DMX line, or keeps a backup desk ready to take over.

The Elumen8 Cygnus MERGE has six modes: HTP (highest takes precedence), LoTP (lowest takes precedence), LTPc and LTPin (latest takes precedence, by channel or by input), Backup and Merge. It also has an RDM filter and opto-isolated outputs. The Cygnus SPLIT8PRO combines both jobs: an eight-way splitter with HTP, LTP, A+B and Backup merge modes, configurable DMX refresh rates and an audible DMX error alarm.

Dual-input splitters such as the GD10 and SPLIT10 are a different thing: they carry two separate signals to different outputs, and neither maker lists a merge mode.

Comparison: DMX splitters we sell

Specifications from each manufacturer’s published product page, manual or launch material. “Not listed” means the maker does not claim it, not that the unit definitely lacks it.

Which one for which job

• Mobile DJ or band rig, one universe: a truss-mount Data Distro 6, or a small QTX DMX-D4 or Transcension S8 at the side of the stage.
• Dimmer or control rack: a 1U unit. Choose the GD10, SPLIT8PRO or Theatrixx xVision 1:8 if you use RDM, or the SPLIT6, Data Stream 4 or D4 Branch RM for plain DMX.
• Two universes from one box: the GD10 in 2×5 mode, or the SPLIT10 or SPLIT8PRO with A/B inputs.
• Backup desk or two operators: the Cygnus MERGE or SPLIT8PRO.
• Outdoor positions: the IP65 GD4IP.
• Architectural install: the DIN-rail GD4D or NASPLIT-4, both low-voltage units.
• Several universes over long distances: run Art-Net or sACN over Ethernet to a node near the fixtures. Switches like the ChamSys GeNetix GS8 carry the network; see Art-Net and sACN nodes explained.

Popular picks from the shop

Frequently asked questions

How many DMX fixtures can I daisy chain?

Plan on 32. DMX512 uses RS-485, which allows 32 unit loads per line segment. Some fixtures draw a fraction of a unit load, but unless the datasheet says so, count each fixture as one. Beyond that, split the line.

Do I need a DMX splitter or a booster?

They are usually the same product. Makers use splitter, booster, buffer, repeater and distributor for an active box that regenerates the signal on each output.

Does every splitter output need a terminator?

Yes. Each output is a separate DMX line, so terminate the last fixture on every run. If you are not using the splitter’s thru socket, terminate its input with the termination switch, or with a terminator plug on units that do not have a switch.

Will my DMX splitter work with RDM?

Only plan on it if the manufacturer says the splitter supports RDM. RDM needs data to travel back from the fixtures through the splitter, and many splitters do not list RDM support. Check for an RDM or DMX+RDM switch, or E1.20 in the specifications.

What does opto-isolated mean on a DMX splitter?

The input and outputs are coupled optically rather than wired together, so an electrical fault on one leg is far less likely to damage the desk or knock out the other legs. Check whether the maker isolates each output individually or in groups.

Can a DMX splitter merge two consoles?

A standard splitter cannot. You need a merger such as the Elumen8 Cygnus MERGE, or a splitter with merge modes such as the Cygnus SPLIT8PRO, which offers HTP, LTP, A+B and Backup.