XLR Connector Pinout: The Standard 3-Pin Assignment, Pin by Pin
Quick answer / TL;DR: Short answer: the standard 3-pin XLR pinout is pin 1 = shield/ground, pin 2 = hot (signal +), pin 3 = cold (signal -). Viewed from the male connector's pins, 1 is the shield, 2 and 3 are the signal pair. A pinout error – swapped 2 and 3, or a shield tied to a signal pin – produces hum, a dead channel, or a phase inversion, all of which a pinout check identifies before the gear is blamed.
The XLR pinout is the small reference that resolves most XLR wiring and troubleshooting questions: which pin carries the shield, which carries the hot signal, which carries the cold. Get the assignment wrong and the result is not silence – it is hum, a dead channel, or a phase inversion that reads as thin sound. The pinout is the first thing to verify when an XLR connection misbehaves.
This is the pin-by-pin reference for the standard 3-pin XLR, viewed from both the male and the female side, with the errors that a pinout check catches.
The Standard 3-Pin Assignment
| Pin | Function | Signal |
|---|---|---|
| 1 | Shield / ground | Noise-rejection shield; the grounding reference |
| 2 | Hot (signal +) | Carries the audio signal |
| 3 | Cold (signal -) | Carries the inverted audio signal |
The balanced design is in pins 2 and 3: the audio travels on both, inverted on one, and the receiver subtracts to cancel the noise the shield rejected. Pin 1 is the reference and the noise-rejection layer, not a signal path.
Viewing the Pinout: Male vs. Female
| Viewpoint | Pin 1 | Pin 2 | Pin 3 |
|---|---|---|---|
| From the male connector (pins, looking at the pins) | Shield | Hot | Cold |
| From the female connector (sockets) | Shield | Hot | Cold |
| Keying | The XLR's mechanical key aligns the pins | Prevents reversed insertion | Same |
The assignment is identical from both viewpoints – pin 1 is the shield on the male and in the female. The mechanical key is what prevents a rotated insertion, which is how a pinout error would otherwise enter a connection.
The Errors a Pinout Check Catches
| Symptom | Pinout error | Fix |
|---|---|---|
| Hum or ground buzz | Shield (pin 1) miswired or open | Restore pin 1 to the shield |
| Dead channel | Hot or cold (pin 2/3) open or swapped to the wrong pin | Restore the signal pair to pins 2 and 3 |
| Thin, hollow sound | Pins 2 and 3 swapped (phase inversion) | Re-align 2 to hot, 3 to cold |
| Intermittent channel | A pin contact is loose | Re-terminate or replace the connector |
Verifying the Pinout
- A continuity check confirms each pin reaches the intended conductor at the far end
- A phase or polarity checker confirms 2 is hot and 3 is cold end to end
- The spec sheet states the wiring – 'straight' means 2 hot / 3 cold aligned at both ends
- A visual check of the connector's pin positions catches a reversed build before it is plugged in
Pinout verification tools and per-connector contact specifications are not provided in the knowledge base. Use a continuity or phase checker for the verification step, and confirm the cable's stated wiring ('straight') against the device's expected polarity.
Real-World Applications
The new-cable check
Before a volume of cables enters a stage or a studio, a sample's pinout is verified – continuity plus phase – so a reversed build is caught before it is patched into a show.
The hum investigation
A channel that hums is a pinout suspect before it is a gear suspect – the shield on pin 1 is checked first, because a miswired or open shield is the most common hum cause at the cable level.
The phase correction
A thin-sounding channel is often pins 2 and 3 swapped. The pinout check identifies the inversion, and the correction is a re-termination or a polarity flip at one end.
Related reading: How the pins get wired in practice? Read the XLR wiring guide — blogs/news/xlr-wiring
Related reading: Browse XLR cables with published pinout specs — collections/audio-cables
Frequently Asked Questions
What does XLR pin 1 do?
Pin 1 is the shield and grounding reference – it carries the noise-rejection shield, not the audio signal. The audio travels on pins 2 (hot) and 3 (cold).
How do I know if pin 2 and pin 3 are swapped on my cable?
A swapped 2/3 produces a phase inversion – the channel works but sounds thin and hollow. A phase checker confirms it, and re-terminating the connector (or using a polarity flip at one end) corrects it.
Is the pinout the same on a 4-pin XLR?
The 3-pin assignment (1 shield, 2 hot, 3 cold) applies to the first three pins. A 4-pin adds a fourth signal for a second channel or a control function – the exact assignment is application-specific, so confirm against the device's manual.
Can a wrong pinout damage equipment?
A swapped signal pair (2/3) does not damage gear – it inverts phase. A shield tied to a signal pin can cause hum and, in a ground-loop situation, can stress the connection. Verify the pinout before energizing a new cable run.
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