XLR Soldering & Pinout
Pro standard XLR soldering guide based on IEC 60268-12. Balanced audio pinout, wiring, and termination best practices.
XLR Pinout Diagram
Standard XLR Pinout (IEC 60268-12)
| Pin | Function | Signal Role | Standard Colour |
|---|---|---|---|
| 1 | Shield (Pin 1) | Cable shield connection | Bare / Drain wire |
| 2 | Hot (+) | Non-inverted signal | Varies by manufacturer (commonly white or red) |
| 3 | Cold (−) | Inverted signal | Varies 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
- Slide boot components onto cable FIRST: Boot (rear shell), then chuck — in correct order. Do this before any stripping.
- Prep cable: Strip outer jacket 20 mm. Unbraid/twist shield into a single drain conductor. Strip inner conductors 6 mm.
- Tin conductors: Heat wire, feed solder to strands (not iron). Shiny, smooth joints only.
- Solder pins in order: 1 → 2 → 3 (or 1 → 3 → 2). Pin 1 (shield/ground terminal) first — its larger cup anchors the cable. Pins 2 and 3 in whichever order gives best access. Both signal pins are equally critical in a balanced pair.
- Inspect & test: Visual — no stray strands, no bridges. Continuity — Pin 1→1, 2→2, 3→3. Shorts — no 2↔3, 1↔2, 1↔3.
- 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
| Application | Cable Type | Impedance | Max Length | Shield Grounding |
|---|---|---|---|---|
| Mic / Line (analogue) | 2-cond. shielded | N/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 data | 110–120 Ω | 300 m (~1000 ft) per ANSI E1.11 (DMX512-A). 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 digital | 110 Ω | 100 m | Both 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. For ground loops in multicore/snake installations, lift Pin 1 at the receive end only; never lift both ends.
Common Faults & Fixes
| Problem | Solution |
|---|---|
| Cold joint — dull, grainy solder | Reheat 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 pins | Twist shield tightly, tin fully. Inspect with magnifier after soldering. |
| Strain relief gripping inner conductors | Leave 10–15 mm jacket inside the chuck. The chuck must grip the jacket, not the wires. |
| Forgotten boot | Prevention: 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 shifts | 3–5 s max per joint. Cool and retry if needed. |