Guides / XLR

XLR Soldering & Pinout

Professional-standard XLR soldering guide based on IEC 60268-12. Balanced audio pinout, wiring and termination best practices.

XLR Rear View, Solder Side (Pin 3 at top) Guiding key at top; Pin 3 at top; Pins 1 & 2 at the bottom. FEMALE (Socket) 3 2 1 3 = COLD (−) 1 = SHIELD 2 = HOT (+) MALE (Plug) 3 1 2 3 = COLD (−) 2 = HOT (+) 1 = SHIELD Solder: shield→1, white/red→2, black/blue→3. Pin numbers identical on both genders (IEC 60268-12). Only the contact type differs: male = pins (filled), female = sockets (rings).

Standard XLR Pinout (IEC 60268-12)

PinFunctionSignal RoleStandard Colour
1Shield (Pin 1)Cable shield connectionBare / Drain wire
2Hot (+)Non-inverted signalVaries by manufacturer (commonly white or red)
3Cold (−)Inverted signalVaries by manufacturer (commonly blue or black)

Pin 2 carries the non-inverted signal; Pin 3 carries the inverted signal. The receiver subtracts Pin 3 from Pin 2 to reject common-mode noise. Wire colours are not standardised. Always verify with a multimeter. Some legacy gear reverses pins 2/3.

Soldering Procedure

  1. Slide boot components onto cable FIRST: Boot (rear shell), then chuck, in correct order. Do this before any stripping.
  2. Prep cable: Strip outer jacket 20 mm. Unbraid/twist shield into a single drain conductor. Strip inner conductors 6 mm.
  3. Tin conductors and cups: Heat wire, feed solder to strands (not iron). Lightly tin each solder cup too. On female connectors, use a thin layer only: overfilling the socket risks a solder bridge to the neighbouring pin. Shiny, smooth joints only.
  4. Solder pins in whichever order suits access, commonly 1 → 2 → 3 or 1 → 3 → 2. Start with the pin that will be hardest to reach once the other joints are in place.
  5. Inspect & test: Visual: no stray strands, no bridges. Continuity: Pin 1→1, 2→2, 3→3. Shorts: no 2↔3, 1↔2, 1↔3.
  6. Assemble: Seat the boot's strain-relief grommet on the jacket (not the conductors). Thread the bushing hand tight. Pull test the strain relief.

Cable Selection by Application

ApplicationCable TypeImpedanceMax LengthShield Grounding
Mic / Line (analogue)2-cond. shieldedN/A (not impedance-critical)Practical limit varies by cable/source. Line level: 200+ m typical. Mic level: 100–300 m depending on cable capacitance and EMI environment.Both ends (XLR-XLR)
DMX-512 (lighting)110–120 Ω data110–120 Ω300 m (~1000 ft) per ANSI E1.27-1 cabling guidance for ANSI E1.11 (DMX512-A) systems. Keep runs well under this for installations with many daisy-chained devices or where RDM (bidirectional) traffic is used.Both ends required
AES3 (digital audio)110 Ω digital110 Ω100 mBoth ends required

Use dedicated 110 Ω cable for DMX/AES3. Standard mic cable has the wrong characteristic impedance, causing signal reflections that lead to data errors. Analogue audio operates at frequencies too low for cable characteristic impedance to be a factor. Choose mic cable by capacitance (pF/m), conductor gauge and shield coverage instead. Default wiring: connect shield to Pin 1 at both ends. This is correct for AES48-compliant equipment and should not itself cause a ground loop. If a ground loop appears in multicore/snake installations, first check for a genuine Pin 1 problem in the equipment (shield wired to circuit ground rather than chassis) before lifting; if a lift is unavoidable, lift Pin 1 at the receive end only, never both ends.

Common Faults & Fixes

ProblemSolution
Cold joint: dull, grainy solderReheat joint, add a small amount of fresh flux-cored solder, then remove the iron and let the joint cool undisturbed. With leaded solder (e.g. 60/40), a good joint appears shiny and smooth. With lead-free solder, a satin or matte finish is normal and does not indicate a fault.
Stray shield strands shorting pinsTwist shield tightly, tin fully. Inspect with magnifier after soldering.
Strain relief gripping inner conductorsLeave 10–15 mm jacket inside the chuck. The chuck must grip the jacket, not the wires.
Forgotten bootPrevention: Always slide the boot onto the cable before any stripping. Make it step one. Fix: If forgotten, desolder all connections, slide the boot onto the cable, then re-solder.
Reversed polarity (pins 2/3 swapped)Polarity inversion causes destructive cancellation when the signal is summed with correctly wired sources (e.g. stereo pairs, multi-mic setups). Continuity test Pin 2→2 and 3→3 before assembly.
Overheated cup: plastic insert melts, pin shifts3–5 s max per joint. Cool and retry if needed.

Also see: SpeakON Wiring Reference: NL2, NL4, NL8 pinout diagrams and wiring configurations for full-range, bi-amp, stereo, bridged mono and 4-way systems.