XLR Microphone Wiring Diagram and Pin Connections

A standard microphone cable uses a 3-pin XLR connector to carry a balanced signal. Getting the pin connections right matters: a single swapped or broken wire can cause hum, silence or a thin, weak sound. This guide shows the standard pinout, how to wire a cable or adapter, and how to confirm the result before you record.

Before you start

Wiring an XLR cable is a purely physical job. It happens entirely on your workbench, and no software, account or online service is involved. You only need recording software later, to confirm that the finished cable works.

Have these items ready:

• Two-conductor shielded microphone cable (a twisted pair inside a braided or foil shield; star-quad cable also works)
• One female XLR connector and one male XLR connector, or the connectors your adapter requires
• Soldering iron, solder and a stand
• Wire strippers and small side cutters
• A multimeter with a continuity mode, or a dedicated cable tester
• Heat-shrink tubing (optional, but useful for insulating the shield wire)

Disconnect the cable from any mixer or audio interface before you work on it, especially if phantom power is switched on. If you are wiring a lavalier or headset connector rather than a full-size XLR, check the manufacturer's documentation first, because mini-XLR pinouts are not standardized across brands.

The standard 3-pin XLR pinout

Nearly all current microphones and audio inputs follow the same convention. Use this as your wiring diagram:

• Pin 1: ground (cable shield)
• Pin 2: hot, or positive (+) signal
• Pin 3: cold, or negative (-) signal

The pin numbers are usually molded into the connector insert next to each pin or solder cup. On the male connector, pins are visible. On the female connector, the matching holes are numbered in the mirror-image layout, so always read the printed numbers instead of judging by position.

A microphone has a male XLR output, so the cable end that plugs into the microphone is female. The other end, which goes to the mixer, interface or preamp input, is male. Signal flows from the female end toward the male end.

Some older equipment used pin 3 as hot. If you are connecting vintage gear, check its manual before assuming the modern convention.

Step-by-step instructions

These steps cover a standard female-to-male microphone cable. The same pin assignments apply at both ends.

• 1. Slide the connector boots, strain-relief sleeves and any heat-shrink onto the cable before you strip it. They cannot be added after soldering.
• 2. Strip the outer jacket back far enough to reach the solder cups comfortably, then unbraid or unwrap the shield and twist it into a single lead.
• 3. Strip a short length of insulation from each inner conductor. Tin the ends of all three leads and fill the solder cups lightly with solder.
• 4. Decide which inner wire color will be hot and which will be cold. Colors vary between cable brands, so the only rule is consistency: use the same color for pin 2 at both ends.
• 5. Solder the shield to pin 1, the chosen hot conductor to pin 2 and the cold conductor to pin 3. Keep each joint clean, with no stray strands touching a neighboring cup.
• 6. If you added heat-shrink over the shield lead, slide it into place and shrink it so the shield cannot touch pins 2 or 3.
• 7. Reassemble the connector, tighten the strain relief so it grips the jacket rather than the solder joints, and repeat the process at the other end.

Some technicians also connect pin 1 to the metal connector shell using the ground lug found on many connectors. Practice varies between studios and installations, so follow your existing standard if you have one. Leaving the shell unconnected is a common default for microphone cables.

Wiring an XLR to 1/4-inch adapter

If your input device only has a 1/4-inch jack, the wiring depends on the plug type:

• Balanced TRS plug: tip to pin 2, ring to pin 3, sleeve to pin 1
• Unbalanced TS plug: tip to pin 2, sleeve to pin 1, with pin 3 usually joined to pin 1 at the XLR end

An unbalanced TS connection loses the noise rejection of a balanced line, so keep such cables short. Do not use an unbalanced adapter with a condenser microphone that needs phantom power, because phantom power requires a balanced connection on pins 2 and 3.

Check the output

Test the cable electrically before you plug it into anything.

• Set the multimeter to continuity mode and confirm that pin 1 connects to pin 1, pin 2 to pin 2 and pin 3 to pin 3 between the two ends.
• Check every pair of pins at the same end (1-2, 1-3 and 2-3). None of them should show continuity.
• If you did not bond the shell, confirm that no pin connects to the metal shell.
• Flex the cable near each connector while testing to reveal intermittent joints.

Then do a listening test. Connect the microphone through the new cable, select your audio interface or mixer as the input device in your recording software or operating system, and set a sensible input level. Enable phantom power only if the microphone requires it. Record a short sample, speaking at your normal distance, and listen on headphones for hum, buzzing, crackles or a hollow tone. Settings such as sample rate are configured in the software and are not affected by the cable, so a wiring fault will show up as noise or signal loss rather than as a format problem.

Common problems and next steps

Most XLR wiring faults produce recognizable symptoms. Match what you hear to the likely cause:

• Hum or buzz: the shield is not connected to pin 1 at one end, or the shield is touching a signal pin. Recheck pin 1 continuity and look for stray shield strands. A ground loop between connected devices can also cause hum even when the cable is wired correctly.
• Condenser microphone gives no signal: phantom power may be off, or pin 1 may be open. Phantom power needs the pin 1 return path to reach the microphone.
• Lower level and more background noise: one signal leg (pin 2 or pin 3) is open, so the input is no longer receiving a proper balanced signal. Test each pin for continuity.
• Thin or hollow sound when two microphones are used together: pins 2 and 3 are swapped in one cable, reversing its polarity. Compare the cable against a known-good one and correct the swap.
• Crackling when the cable moves: a cold or cracked solder joint, or strain relief that is not gripping the jacket. Reflow the joint and tighten the clamp.
• No sound at all: check that the female end goes to the microphone, that the correct input device is selected, and that the input channel is not muted.

Ribbon microphones need extra care. A miswired or shorted cable combined with phantom power can risk damaging some ribbon elements, so test the cable fully before using it with one, and follow the microphone manufacturer's guidance on phantom power.

If the cable passes every continuity check but the problem remains, swap in a known-good cable and a different input channel. That isolates whether the fault lies in the cable, the microphone or the input device.