XLR Connector Diagram

XLR Connector Diagram — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable xlr connector diagram: download the diagram as SVG or open it and print to paper or PDF.

The XLR connector carries balanced audio signals and phantom power on three pins, providing noise rejection over long cable runs essential in professional live sound and studio recording.

The XLR connector is the standard for professional balanced audio in recording studios, live sound reinforcement, and broadcast. The three-pin version (XLR3) is by far the most common and carries a balanced differential signal plus a chassis ground. The pin assignment is standardised by IEC 60268-12 and followed universally in professional audio:

- Pin 1: Ground / cable screen (shield). The outer braid or foil screen of the cable is connected here. Pin 1 should connect to the chassis ground of the equipment at both ends of the cable — not to the signal ground of the audio circuitry, to avoid ground loops. This is the basis of the 'Pin 1 problem' debated in professional audio design. - Pin 2: Signal positive (Hot, +, In phase). The non-inverting signal conductor. - Pin 3: Signal negative (Cold, −, Out of phase). The inverting signal conductor.

A balanced connection transmits two copies of the same audio signal: the hot copy on pin 2 and an inverted copy on pin 3. Any noise (electromagnetic interference, hum) picked up along the cable affects both conductors equally and in phase. At the receiving equipment, a differential amplifier subtracts pin 3 from pin 2: the audio signals add together (2× amplitude) while the common-mode noise cancels — this common-mode rejection is typically 40–80 dB on well-designed equipment.

Phantom power (+48 V DC, per IEC 61938) is supplied through the same three-pin XLR cable to power condenser microphones and active DI boxes. The +48 V is applied equally to pins 2 and 3 via matched resistors (typically 6.81 kΩ each) at the mixing console or microphone preamplifier, relative to pin 1 ground. Because the voltage is applied identically to both signal conductors, it has no differential effect and does not appear in the audio signal path. Dynamic microphones and passive ribbon microphones do not use phantom power, but correctly designed equipment is unharmed by phantom power on the cable.

The XLR connector itself uses a locking mechanism — a spring-loaded latch on the male plug engages a catch on the female socket, preventing accidental disconnection during a live performance. The male XLR (pins visible) is used on cable ends and on equipment outputs; the female XLR (socket, pins recessed) is used on equipment inputs and microphones. This convention makes the signal flow direction easy to trace.

XLR5 (five-pin) is used for stereo headset microphones and some DMX lighting control applications. DMX512 (stage lighting control protocol) originally used XLR5, though XLR3 is commonly (if incorrectly) substituted in practice.

How to wire xlr connector diagram

Strip and prepare the balanced cable Balanced microphone cable contains two individually insulated conductors (typically one red/hot and one white/black/cold) surrounded by a braided or foil screen and an outer jacket. Strip the outer jacket back approximately 30–40 mm. Separate the screen (braid or foil with drain wire) from the two inner conductors. Strip 5–7 mm of insulation from each inner conductor and tin lightly with solder.
Thread the cable through the XLR shell and strain relief before soldering XLR connectors are assembled in order: slide the cable through the backshell (barrel), then the strain relief/clamp, before soldering. Forgetting this step means the connector must be unsoldered and rebuilt. Tighten the strain relief after soldering so the cable, not the solder joints, bears any tension.
Solder pin 1 to the screen/shield Fold the braided screen back over the outer jacket or gather the drain wire. Cut it to an appropriate length to reach pin 1 without excess. Solder the screen to pin 1. Apply heat briefly — extended heating can melt nearby insulation. Verify the screen does not contact pins 2 or 3.
Solder pin 2 to the hot (positive) conductor The red or positive-marked inner conductor connects to pin 2. Ensure the tinned wire end makes solid contact in the pin solder cup before applying heat. A cold solder joint at pin 2 causes intermittent audio dropouts — one of the hardest faults to trace in a live sound rig.
Solder pin 3 to the cold (negative) conductor The white, black, or negative-marked inner conductor connects to pin 3. Verify the colour convention of your specific cable before soldering. Some cable manufacturers use black for hot and red for ground — always check the cable datasheet.
Assemble the connector shell and test Slide the backshell forward and tighten. Connect the cable between a signal source and a balanced input. Verify audio is present and noise-free. Use a cable tester or multi-meter (continuity mode) to confirm pin-to-pin continuity matches the wired connections and that no shorts exist between pins.

Specifications

Standard pin assignment (IEC 60268-12)	Pin 1 = Ground/Shield; Pin 2 = Hot (+); Pin 3 = Cold (−)
Phantom power voltage (IEC 61938)	+48 V DC (±4 V), also +12 V and +24 V variants exist
Phantom power feed resistors	6.81 kΩ ±1% per leg (pins 2 and 3 to +48 V)
Common-mode rejection ratio (typical)	40–80 dB (better in well-designed differential receivers)
Maximum cable length (professional use)	Typically up to 100 m; capacitance and skin effect limit high-frequency response above this length
Contact plating	Nickel or gold over copper; gold preferred for low-level signal applications for corrosion resistance
Applicable standard	IEC 60268-12 (XLR pin assignment), IEC 61938 (phantom power), AES48 (Pin 1 grounding practice)

Safety warnings

Phantom power (+48 V DC) is present on pins 2 and 3 of an XLR input when phantom is enabled. While 48 V DC is not typically lethal, it can deliver a significant jolt through the pins if touched. Disable phantom power at the mixing console or preamplifier before disconnecting XLR cables during a live show.
Do not connect XLR connectors carrying phantom power to unbalanced equipment (such as a guitar amplifier instrument input) without a purpose-built direct injection (DI) box. Phantom power fed directly to a transformer-less unbalanced input can damage the input stage.
When soldering XLR connectors, ensure adequate ventilation — flux fumes from solder are an irritant. Use rosin-core solder and work in a ventilated area.
Verify cable continuity with a cable tester before use in a live or recording environment. A pin 1 and pin 2 short inside an XLR connector sends phantom power directly to ground, causing a loud noise and potentially damaging the console preamplifier circuit.

Tools needed

Soldering iron (25–40 W) with a fine chisel or conical tip for small connector pins
Suitable solder (rosin-core, 0.7–1.0 mm diameter)
Wire strippers sized for the cable conductors and outer jacket
Side cutters / flush cutters
Helping hands or cable vice to hold the connector during soldering
XLR cable tester or multi-meter (continuity mode) for verification after assembly

Common mistakes

Assembling the XLR shell and strain relief after soldering — requires full rework to correct.
Soldering the screen to pin 3 and the cold conductor to pin 1 — this breaks the balanced circuit; the shield is now part of the signal path and picks up noise.
Leaving a whisker of screen braid wire contacting pin 2 or pin 3 — causes a short to ground, killing the signal.
Using standard speaker cable (two parallel conductors, no screen) instead of balanced microphone cable — the unscreened cable picks up hum and radio frequency interference over long runs.
Not tightening the strain relief — the solder joints bear all cable movement and fail prematurely.

Troubleshooting

Hum or buzz present in audio that disappears when the cable is unplugged: Cause: Ground loop — pin 1 is completing a ground loop between two pieces of equipment connected to different mains earth points at slightly different potentials. Fix: Use a DI box with a ground-lift switch to break the loop at pin 1 on one end. Alternatively, ensure both pieces of equipment share the same mains power distribution and earth point. Check that pin 1 is connected to chassis ground (not signal ground) inside each equipment unit.
Audio signal is present but very low level and sounds thin: Cause: Pins 2 and 3 are shorted together inside the connector — the balanced signals cancel each other at the differential receiver, leaving only any asymmetry as an output. Fix: Open the connector and visually inspect for solder bridges. Use a multi-meter in continuity mode between pins 2 and 3 — no continuity should exist between them.
Intermittent audio dropout when the cable is moved: Cause: Cold or cracked solder joint at one of the pin cups, caused by movement stress, or a conductor strand that was insufficiently tinned before soldering. Fix: Open the connector, flex the cable while monitoring the audio, and identify the intermittent pin. Re-solder the joint: add fresh flux, re-heat until the existing solder flows, and remove the iron. Ensure the cable is stationary while the joint cools.

Frequently asked questions

Which end of an XLR cable has the male connector and which has the female?

By professional audio convention, the male XLR (pins protruding) is on the source/output end of the cable, and the female XLR (recessed socket) is on the destination/input end. Microphones use a female XLR on the body; mixing consoles have female XLR inputs. This means signal flows from the male connector into the female.

What is phantom power and can it damage my microphone?

+48 V phantom power is a DC supply sent through pins 2 and 3 of an XLR cable to power condenser microphone capsule electronics. Dynamic microphones are unaffected by correctly applied phantom power because their output is transformer-coupled. Vintage ribbon microphones with no transformer can be damaged — check manufacturer specifications before enabling phantom power.

Why does a balanced XLR connection reject noise better than an unbalanced jack cable?

A balanced line carries the audio on two conductors: one in phase (pin 2) and one inverted (pin 3). Any noise induced on the cable affects both conductors equally. The differential receiver at the far end subtracts pin 3 from pin 2, which doubles the audio signal amplitude while the common noise cancels — common-mode rejection of 40–80 dB, corresponding to 100× to 10,000× noise reduction versus an unbalanced connection.

Can I connect an XLR output directly to an unbalanced (TS or RCA) input?

Yes, with an appropriate adapter cable, but you lose the noise rejection benefit. Connect pin 1 and pin 3 together to the sleeve (ground) of the TS or the shield of the RCA, and pin 2 to the tip/centre conductor. If pin 3 is left floating, some equipment hums due to the inverting output driving nothing. Never short pin 2 and pin 3 together — this loads the output and may cause distortion.

What does 'pin 1 problem' mean in audio equipment design?

The 'pin 1 problem' refers to XLR pin 1 (shield/ground) being connected to the signal ground of the audio circuitry inside equipment rather than to the chassis. This allows shield-borne interference currents to flow through the signal reference, producing audible hum or noise. Correct practice connects pin 1 directly to the equipment chassis at the XLR socket.