The shell is the same, the job is not
A three-pin and a five-pin XLR look like the same connector and are not interchangeable. The barrel dimensions follow one international standard, so they feel consistent in the hand, but the contact count decides what the connector can carry.
That is the reason pin count is one of the first things a cable specification should state, ahead of shell material or plating.
Three-pin: the default for balanced analogue audio
Three-pin XLR is the standard connector for balanced analogue audio. The arrangement is one ground, one signal, one return — enough for a single balanced channel.
If a specification does not state a pin count, three-pin is the assumption most suppliers will make, because it is the most common format in audio.
Four-pin: intercom and headset systems
Four-pin XLR is used for monaural intercom headsets and handsets. Production intercom systems use it to carry the microphone signal in one direction and the headphone signal in the other, over a single connector.
Four-pin also appears in low-voltage power applications on some equipment. If a four-pin connector is being specified, the wiring convention matters more than the pin count, because the two directions share the shell.
Five-pin: DMX512, and stereo balanced audio
Five-pin XLR is the connector the DMX512 standard specifies for lighting control. It carries the primary data pair plus a second pair, and it is the format used across stage lighting.
Five-pin is also used for dual-channel balanced audio where two channels run through one connector.
There is a trap here worth knowing before ordering: audio and DMX reverse the assignment of pins 2 and 3. A cable built for one purpose is not safely used for the other, even when the shell fits.
Six-pin: dual-channel intercom and stereo headsets
Six-pin XLR appears in dual-channel intercom systems and in professional stereo headsets that combine a balanced microphone with stereo headphones in a single connector. It is a specialist format — specified for a particular piece of equipment rather than chosen as a general-purpose connector.
Seven-pin: broadcast and multi-channel applications
Seven-pin XLR is used for specialised broadcast equipment and multi-channel applications where several signals must share one connector. Like six-pin, it is specified to match the equipment at both ends.
Choosing between them
| Pin count | Primary use |
|---|---|
| 3 | balanced analogue audio |
| 4 | intercom headsets, some low-voltage power |
| 5 | DMX512 lighting control; dual-channel balanced audio |
| 6 | dual-channel intercom; stereo headsets with balanced mic |
| 7 | broadcast and multi-channel equipment |
The decision rule is equipment-led, not preference-led. The connector must match what is on the other end of the cable, and if the two ends disagree, the correct fix is an adapter built for that purpose, not a cable wired to guesswork.
What to write on the specification
State the pin count, the gender of each end, and the intended signal. A line such as 3-pin male to 3-pin female, balanced audio removes the ambiguity that a bare part number leaves.
For DMX work, state the pin count as five-pin and say it is for lighting control. That single line prevents an audio connector from being supplied for a lighting run.
Adapters, and when they are the right answer
A mismatch between two ends is common: equipment with a three-pin socket feeding a system that expects five-pin. The correct response is an adapter wired for that specific pairing.
The point to watch is that an adapter changes the connector, not the cable. If the signal is DMX, the cable between the adapter and the equipment still has to be a DMX-rated twisted pair. An adapter solves the mechanical problem only, and a lighting run built from audio cable will still behave badly however well the connectors fit.
Two checks before ordering
Check the equipment at both ends. Pin count, gender, and the signal each socket carries. Two sockets with the same pin count can still be wired for different purposes.
Check whether the equipment uses all the pins. Some lighting equipment uses only three of the five contacts even though the connector is five-pin. That is a property of the equipment, not a reason to specify a three-pin connector for the run.
Summary
- The shell is standardised; the contact count is not.
- 3-pin for balanced audio, 5-pin for DMX, 4-pin for intercom.
- 6-pin and 7-pin are equipment-specific formats.
- Audio and DMX reverse pins 2 and 3 — never assume a fit means a match.
What each pin on a 3-pin XLR carries
Balanced audio equipment uses one assignment: pin 1 is the screen (ground), pin 2 is the in-phase signal (hot, written +) and pin 3 is the return (cold, written −). The screen surrounds the two signal conductors, and the signal itself travels as the difference between pin 2 and pin 3 rather than as a voltage against ground.
That is the reason the cable behind the connector is a two-core shielded construction and not a single conductor: the pair carries the signal, the shield carries the screen. It is also why the screen is connected at the connector shell rather than being used as a signal path.
The assignment is standard. What is not standard is assuming it: audio and DMX512 reverse pins 2 and 3, so a cable built for one purpose is not safely used for the other even though the shell and the contact count are identical.
Two cores plus a shield, or “three conductor” cable
The same balanced microphone cable is sold under three different names depending on which counting system the supplier uses, and buyers hit this confusion constantly when comparing quotations:
| Counting system | What it counts | Balanced microphone cable |
|---|---|---|
| By core | insulated signal conductors only | 2 core |
| By total conductor | signal conductors plus the shield counted as one | 3 conductor |
| By pair | twisted signal pairs | 1 pair |
All three describe one construction. When a quotation says 3 conductor and another says 2 core shielded, the question to ask is whether the shield is being counted, not whether the cables differ. For speaker cable the count is always by core, because there is no signal return conductor to count — do not carry the “conductor” wording across to speaker cable.
Choosing the cable that goes on the connector
Pin count decides the connector. Conductor size and construction decide how the run behaves. The published construction of the LBS microphone cable range differs on exactly two axes — conductor size and whether the cable is supplied as bulk cable or as a finished assembly — and the routing category printed on each specification is the selection rule:
| Variant | Conductor | O.D. | Conductor resistance | Routing category |
|---|---|---|---|---|
| 2-core shielded, 2×0.3 mm², bulk | tinned copper, PE insulation | 6.0 – 6.5 mm | ≤55 Ω/km | Standard routing |
| 2-core shielded, 2×0.5 mm², bulk | tinned copper, PE insulation | 6.8 – 7.2 mm | ≤40 Ω/km | Long distance routing |
| finished XLR patch, 2×0.3 mm² | tinned copper, 3-pin XLR male / female | 6.0 – 6.5 mm | ≤55 Ω/km | Standard patching |
| finished XLR patch, 2×0.5 mm² | tinned copper, 3-pin XLR male / female | 6.8 – 7.2 mm | ≤40 Ω/km | Long distance patching |
All four are double shielded (AL-Foil Mylar plus tinned-copper braid), 50–70 Ω characteristic impedance, ≤120 pF/m core-to-core capacitance, rated 30 V and −20 °C to +70 °C. The bulk variants are supplied for termination onto 3-pin XLR or TRS connectors; the finished variants are assembled XLR male-to-female patch cables with zinc alloy shells and nickel-plated contacts.
Two consequences follow from the table. If a run is short and the cable is being terminated on site, 2×0.3 mm² is the standard-routing construction. If the run is long, the 0.5 mm² construction halves the conductor resistance (≤40 Ω/km against ≤55 Ω/km) and is the one the specification calls long-distance routing. Choosing between bulk and finished is a labour question, not a signal question — both use the same cable construction at the same size.
Where the same three-pin wiring repeats across many channels inside one jacket, the pin convention has to hold for every channel and the channel numbers have to survive termination at both ends. That is a drawing problem more than a connector problem, and it is covered in the 8-channel audio snake cable guide.
Frequently asked questions
Can I use a 3-pin XLR for DMX?
Three-pin connectors are widely used on lighting equipment in practice, but the DMX512 standard specifies a five-pin connector. If the equipment at both ends is three-pin, that is the format to build; the cable still needs DMX-suitable impedance.
Is a 5-pin XLR for audio or lighting?
Both. Five-pin is the standard DMX512 connector and is also used for dual-channel balanced audio. The pin assignment differs between the two uses.
Do all XLR connectors fit each other?
The shell is dimensionally standardised, so a 3-pin plug can physically enter a 5-pin socket in some designs. Fitting is not the test — the contact count and wiring must match the signal.
What is the pin count for intercom headsets?
Four-pin is the common format for monaural intercom headsets. Check the equipment manual, because wiring conventions differ between intercom manufacturers.
Is 2-core shielded cable the same as 3-conductor cable?
Yes, for a balanced microphone cable. Two insulated signal cores plus one shield are three conductors in total, so the same cable is listed as 2 core by one counting system and 3 conductor by another. Ask the supplier which convention the figure uses before treating two quotations as different constructions.
Can I use microphone cable for a 3-pin DMX run?
Only if the cable’s impedance suits the DMX512 run. Microphone cable is a 50–70 Ω balanced audio construction; DMX512 cable is a 120 Ω twisted pair, and that is the construction to specify for lighting control. A 3-pin connector that fits does not make an audio cable a data cable.
For lighting control over a 5-pin XLR, the cable behind the connector is DMX512 lighting control cable rather than audio cable: LBS lists it as the single-shielded LBSDMX144050 and the double-shielded LBSDMX144050-2.
Continue reading
- 2-Core Shielded Balanced Microphone Audio Cable — 2×0.5 mm² — the bulk cable to terminate onto 3-pin XLR.
- Finished XLR Microphone Patch Cable — 2×0.5 mm² — the assembled 3-pin XLR male-to-female equivalent.
- Professional XLR Connector, 3-pin to 7-pin — the connector family for these assemblies.
- Audio signal cable range — microphone, multicore and balanced audio cable.
- Connector range — XLR, TRS and speaker twist lock connectors.
- Balanced microphone cable: how shielding protects the signal
- DMX cable vs microphone cable — why the two cannot be swapped.
- Cable cores vs pairs vs conductors — the counting systems in full.