{"id":1295,"date":"2026-11-02T11:07:50","date_gmt":"2026-11-02T11:07:50","guid":{"rendered":"http:\/\/lbscable.com\/en\/2026\/11\/02\/dmx-5-pin-vs-3-pin-cable\/"},"modified":"2026-11-02T11:13:46","modified_gmt":"2026-11-02T11:13:46","slug":"dmx-cable-impedance-120-ohm","status":"publish","type":"post","link":"https:\/\/lbscable.com\/en\/2026\/11\/02\/dmx-cable-impedance-120-ohm\/","title":{"rendered":"DMX Cable Impedance: Why 120 \u03a9 Decides the Run, Not the Pin Count"},"content":{"rendered":"

Short answer: the connector does not decide whether a DMX run works \u2014 the cable does. DMX512 is a 120 \u03a9 RS-485 bus, and a run fails when the cable presents the wrong characteristic impedance, not when the connector has three pins instead of five.<\/strong><\/p>\n

This page covers the electrical side: what impedance does to the signal, why microphone cable is the wrong substitute, and what to specify when ordering DMX512 cable. For the connector pinout itself \u2014 which pin carries what on 3-, 4-, 5-, 6- and 7-pin XLR \u2014 see XLR pin counts explained<\/a>, which covers that side in full.<\/p>\n

The short version of the connector question, since it comes up constantly: pins 1, 2 and 3 carry signal common, data\u2212 and data+. Pins 4 and 5 exist for a second data link that almost no fixture implements, which is why 3-pin caught on commercially even though the standard defines 5-pin. Neither choice changes signal quality. The cable behind the connector does.<\/p>\n

Pin assignment: what each pin actually carries<\/h2>\n\n\n\n\n\n\n\n\n\n
Pin<\/th>\nFunction<\/th>\nUsed on 3-pin?<\/th>\n<\/tr>\n<\/thead>\n
1<\/td>\nSignal common \/ shield<\/td>\nYes<\/td>\n<\/tr>\n
2<\/td>\nData 1\u2212 (primary data link, negative)<\/td>\nYes<\/td>\n<\/tr>\n
3<\/td>\nData 1+ (primary data link, positive)<\/td>\nYes<\/td>\n<\/tr>\n
4<\/td>\nData 2\u2212 (optional secondary data link)<\/td>\nNo<\/td>\n<\/tr>\n
5<\/td>\nData 2+ (optional secondary data link)<\/td>\nNo<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Three conductors carry the working signal. Pins 4 and 5 exist for a second, independent data link that almost no manufacturer implements \u2014 in practice they are unused in the overwhelming majority of rigs. That is precisely why 3-pin caught on: it carries everything that is actually used.<\/p>\n

Why the standard specifies 5-pin anyway<\/h2>\n

DMX512-A (ANSI E1.11) defines the 5-pin XLR as the official connector. The reasoning is separation of concerns rather than signal quality: the extra pair leaves room for a secondary link, and a distinct connector type stops a DMX run from being plugged into an audio circuit by mistake.<\/p>\n

That last point matters more than it sounds. A 3-pin DMX output and a 3-pin audio output are physically identical. In a venue with both microphone lines and lighting control, the wrong patch is one tired technician away \u2014 and a console output driven into a microphone input is an expensive mistake.<\/p>\n

Why 3-pin persists in the market<\/h2>\n

Cost and fixture design. A large share of low-cost LED fixtures ship with 3-pin sockets because the connector is cheaper and smaller. Rental houses then stock 3-pin cable to match, and the practice reinforces itself.<\/p>\n

The practical consequence for a buyer: if you are equipping a rig where fixtures come from several suppliers, you will end up needing both, or you will need adapters. Adapters introduce a mechanical joint in the middle of a data line, which is the single most common place for a lighting fault to appear.<\/p>\n

The part that actually decides whether your run works<\/h2>\n

Impedance. DMX512 is a digital bus running on RS-485 differential signalling, and the cable must present a characteristic impedance of 120 \u03a9. A cable with the wrong impedance produces reflections at the far end of the run, and reflections corrupt data frames. The symptom looks like a control problem \u2014 flickering, missed cues, a fixture that drops out at the end of a chain \u2014 so people replace the fixture instead of the cable.<\/p>\n

What a compliant DMX cable looks like from the factory side:<\/p>\n\n\n\n\n\n\n\n\n
Property<\/th>\nRequirement<\/th>\nWhy<\/th>\n<\/tr>\n<\/thead>\n
Characteristic impedance<\/td>\n120 \u03a9<\/td>\nRS-485 bus termination; wrong impedance = reflections<\/td>\n<\/tr>\n
Conductors<\/td>\n1 twisted pair<\/td>\nDifferential pair must be twisted to reject common-mode noise<\/td>\n<\/tr>\n
Shield<\/td>\nFoil and\/or braid<\/td>\nDimmer racks and switch-mode supplies are electrically noisy<\/td>\n<\/tr>\n
Capacitance<\/td>\nLow, controlled<\/td>\nHigh capacitance rounds off the data edges over distance<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

LBS publishes 120 \u03a9 on every DMX512 model in the catalogue. The single-shielded range uses one foil or braid layer for install and short-run work; the double-shielded range adds a 100% coverage aluminium foil plus a heavy-duty tinned-copper braid, which is what rental and touring companies specify where cable shares a truss with dimmer and LED driver cabling.<\/p>\n

Can you run DMX over a 3-pin microphone cable?<\/h2>\n

It will often work, and that is exactly the problem \u2014 “often” is not a specification. Microphone cable is typically 60\u201380 \u03a9 with higher capacitance, so a mic cable used as a DMX line degrades the signal in a way that only shows up at longer distances, at higher channel counts, or in a noisy electrical environment. The fault appears later, in front of an audience, on a cable that tested fine on the bench.<\/p>\n

There is a second reason a factory will push back on this: a 3-pin DMX cable and a 3-pin mic cable are indistinguishable once the jacket is printed, so mixed inventory becomes a permanent source of rig faults.<\/p>\n

Decision table<\/h2>\n\n\n\n\n\n\n\n\n\n
Your situation<\/th>\nConnector<\/th>\nCable<\/th>\n<\/tr>\n<\/thead>\n
Permanent install, single fixture brand<\/td>\nMatch the fixture<\/td>\n120 \u03a9, single shield<\/td>\n<\/tr>\n
Rental \/ touring, mixed fixture brands<\/td>\n5-pin standard plus 3-pin adapters on the shelf<\/td>\n120 \u03a9, double shield<\/td>\n<\/tr>\n
Mixed audio and lighting in one venue<\/td>\n5-pin only \u2014 physically prevents mis-patching<\/td>\n120 \u03a9, double shield<\/td>\n<\/tr>\n
Long runs or electrically noisy truss<\/td>\nEither<\/td>\n120 \u03a9, double shield, terminated at the far end<\/td>\n<\/tr>\n
Distributor building a stock range<\/td>\nBoth, clearly labelled<\/td>\n120 \u03a9 only \u2014 do not substitute mic cable<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

What to specify when you order<\/h2>\n

Four numbers settle the specification: characteristic impedance (120 \u03a9), conductor count and cross-section (2-core, typically 2 \u00d7 0.25 mm\u00b2 to 2 \u00d7 0.50 mm\u00b2 for control runs), shield construction (single or double), and jacket (matte PVC is the usual choice for touring because it does not mark truss or floor). Everything else is preference.<\/p>\n

The LBS DMX512 range covers 64\/2\u00d70.25 through 168\/2\u00d70.50 in both single-shielded and double-shielded constructions, in 100 m rolls and cut lengths, with the connector assembled to your specification. If you are building a private-label range, the model, shield type, jacket colour and print are all configurable \u2014 see the DMX and lighting control cable range<\/a> for the published specifications, or the 128\/2\u00d70.35 single-shielded model<\/a> as a reference data sheet.<\/p>\n

Frequently asked questions<\/h2>\n

Is 3-pin DMX cable worse than 5-pin?<\/h3>\n

The pin count does not change signal quality \u2014 pins 4 and 5 are unused. What matters is whether the cable behind the connector is 120 \u03a9. A 3-pin cable made from proper 120 \u03a9 DMX stock performs identically to a 5-pin cable made from the same stock.<\/p>\n

Can I use a 5-pin to 3-pin adapter?<\/h3>\n

Yes, and it is common in rental inventory. The caveat is mechanical: every adapter adds a joint, and joints are where intermittent faults start. For permanent installs, terminate in the connector the fixture uses.<\/p>\n

How far can DMX run on 120 \u03a9 cable?<\/h3>\n

Distance is limited by the cable’s capacitance and by the electrical noise in the venue, not by a single published number \u2014 which is why touring companies specify double-shielded stock for long truss runs while single-shielded stock is used for short install runs. Ask the cable supplier for the capacitance figure of the specific model and size the run from that.<\/p>\n

Does the shield need to be connected at both ends?<\/h3>\n

The shield is the signal common (pin 1) and is carried through the chain. It should be terminated at the end of the run per the controller and fixture instructions, not left floating.<\/p>\n

Can I order DMX cable with connectors already fitted?<\/h3>\n

Yes. LBS supplies DMX512 cable in rolls and as assembled cables with 3-pin or 5-pin XLR connectors, in the lengths and branding you specify.<\/p>\n

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