Reference
One connector, six circuits, and no agreement about what is in them
A 19-pin Socapex carries six three-conductor circuits. What those circuits are is not part of the connector: on a lighting truck they are six 16 A mains feeds, and on an audio truck the same shell, on the same size of cable, is very often a loudspeaker loom fanned out to NL4s.
Those two cables mate perfectly with each other. A speaker loom plugged into a dimmer or a distro puts mains voltage on loudspeaker terminals and into the output stage of whatever is connected to them. The reverse — a lighting loom into an amplifier rack — is merely useless. Nothing mechanical prevents either, and this is the single most consequential thing on the page.
Below: the pinout, validated at build time because a wrong mains pinout published on a website is a hazard in its own right; a computed table of what loom length and conductor size do to volt drop and to damping factor; and an honest account of the audio multipins, where the answer to "what is the pinout" is that there isn't one.
The 19-pin Socapex pinout
| Circuit | Live | Neutral | Earth |
|---|---|---|---|
| 1 | 1 | 2 | 13 |
| 2 | 3 | 4 | 14 |
| 3 | 5 | 6 | 15 |
| 4 | 7 | 8 | 16 |
| 5 | 9 | 10 | 17 |
| 6 | 11 | 12 | 18 |
Pin 19: Not connected. Some sources describe it as a centre alignment pin; a few assemblies land the cable screen on it.
A circuit is an adjacent live/neutral pair plus an earth from the 13–18 block. That layout matters: keeping all six earths together and above the live pins means a partially-mated or damaged connector is far less likely to present a live pin against an earth of a different circuit.
You will also find the claim that the six lives are on pins 1–6 and the neutrals on 7–12. Three independent sources give the interleaved arrangement above and none that were checked gave the other, so it is what is printed here — but the existence of the disagreement is itself the reason to meter a loom of unknown provenance rather than trust any table, this one included.
Commoning the earths inside the connector is common practice in the UK and is not permitted in the US, where each circuit's earth must remain separate. That is a wiring-regulations difference rather than a preference, and it travels with the loom rather than with the venue.
What length costs you, either way
The same copper, judged by two completely different standards. Loop resistance isρ × 2L ÷ A with copper at1.724 × 10⁻⁸ Ω·m — there and back, which is the factor most quick estimates drop.
| conductor ↓ length → | 10 m | 20 m | 30 m | 50 m |
|---|---|---|---|---|
| 1.5 mm² | 0.23 Ω1.6% drop at 16 Adamping 35:1 | 0.46 Ω3.2% drop at 16 Adamping 17:1 | 0.69 Ω4.8% drop at 16 Adamping 12:1 | 1.15 Ω8.0% drop at 16 Adamping 7:1 |
| 2.5 mm² | 0.14 Ω1.0% drop at 16 Adamping 58:1 | 0.28 Ω1.9% drop at 16 Adamping 29:1 | 0.41 Ω2.9% drop at 16 Adamping 19:1 | 0.69 Ω4.8% drop at 16 Adamping 12:1 |
| 4 mm² | 0.09 Ω0.6% drop at 16 Adamping 93:1 | 0.17 Ω1.2% drop at 16 Adamping 46:1 | 0.26 Ω1.8% drop at 16 Adamping 31:1 | 0.43 Ω3.0% drop at 16 Adamping 19:1 |
- On mains, the number to watch is the percentage. UK practice allows about 3% volt drop for lighting and 5% for other uses, measured from the origin of the installation — so the loom is only part of a budget that also includes everything upstream of it. A 50 m run of 2.5 mm² comes to 4.8% at a full 16 A, which exceeds a 3% lighting allowance on the loom alone — before anything upstream has been counted at all.
- On loudspeakers, the number to watch is damping. An amplifier with a damping factor of 500 into 8 Ω sees that figure collapse to whatever the cable allows — 12:1 on a 50 m run of 2.5 mm², because the cable resistance swamps the amplifier's output impedance entirely. Below about 20:1 the control over a woofer's motion is audibly reduced, and no amount of amplifier specification recovers it.
- Power lost in the cable is the same arithmetic. That 0.69 Ω against an 8 Ω load throws away about 8% of the amplifier's output as heat in the loom — close to half a decibel, before any consideration of damping.
- Copper gets worse when it gets hot. These figures are at 20 °C. A loom coiled on a drum in the sun, carrying its full rating, is meaningfully more resistive than the table says, and a coiled loom also cannot dissipate what it is generating.
Your loom, both ways at once
The same numbers as the table above, at whatever length and section you actually have — and judged by both standards side by side, because that is the argument of this page. One loom, two completely different failure criteria.
This calculator needs JavaScript. The table above covers three sections at four lengths.
The mains figure is the loom alone and takes no account of anything upstream of it, which is where the rest of your 3% goes. The damping figure assumes an amplifier of infinite damping factor, so it is the ceiling the cable imposes rather than what you will measure — a real amplifier can only be worse.
The audio multipins, and why there is no pinout here
This is the fourth page in this section to arrive at a version of the same finding, and here it is at its starkest. DMX has ANSI E1.11. Ethernet has TIA-568. Analogue audio over Cat5 has AES72, which at least catalogues nine incompatible options.Audio multipin connectors have nothing at all — the shell, the contact count and the gender are standardised, and which pin carries channel 1 hot is whatever the assembler decided.
So this page does not print a channel map for any of them. A confident-looking table would be the most harmful thing on this site: it would be right for some looms, wrong for others, and indistinguishable between the two until something was plugged in.
| Family | Sizes | Shell | Typically carries | Channel mapping |
|---|---|---|---|---|
| EDAC / ELCO | 20, 38, 56, 90 and 120 pin | Rectangular, genderless contacts in a shell with a screw or latch | 56-pin is the classic 18–24 channel audio multi; 120-pin appears on large frames | Not standardised |
| VEAM / Socapex audio | Commonly 37 and 61 pin | Circular, threaded coupling, same family as the lighting shells | 12 channels on 37-pin, 20 on 61-pin, at three pins per channel | Not standardised |
| Harting Han | Modular — Han 24, 40, 72 and larger | Rectangular hoods with interchangeable inserts | Whatever the insert carries; frequently mixed audio, power and data in one hood | Not standardised |
| Whirlwind W-series | Manufacturer series, various | Multiple, depending on series | Multi-channel stage boxes and fan-outs | Manufacturer's own, documented |
- EDAC / ELCO — The contacts are genderless — the same part is used at both ends and the shell decides orientation. Widely used on patchbays, consoles and older tie-lines, and wired differently by nearly everyone who uses it.
- VEAM / Socapex audio — Rugged and expensive, and the usual choice where an audio multi has to survive touring. The circular shell resembles the 19-pin lighting connector at a glance and is a different insert entirely.
- Harting Han — The insert system is the point: one hood can carry an audio insert, a power insert and a data insert side by side. It also means two identical-looking hoods can be wired to completely different purposes.
- Whirlwind W-series — Named conventions rather than a standard, but Whirlwind at least publish theirs — which puts them ahead of most of this category.
Working out an unknown audio multi
The same method as identifying an unknown Cat5 stagebox, and about as quick:
- Establish the screen convention first. Meter every pin against the shell — the screens are usually commoned and will show up immediately as a block.
- Take one XLR at the fan-out end and buzz its pin 2 against every multipin contact until it beeps. That is channel 1 hot.
- Repeat for pin 3. Two readings give you the pattern — per-channel triples, or all the hots in a block followed by all the colds.
- Confirm the pattern on the highest-numbered channel rather than the second one. A scheme that runs in blocks and one that runs in triples agree on channel 1 and diverge from there.
Sources
- The 19-pin Socapex pinout — three independent sources, all giving the same interleaved arrangement: Phase 3 Connectors' wiring diagram, Electronics 2000's pinout page, and Stagecraft Production Service's break-in/break-out diagrams, which also give the conductor colours. Wikipedia's Socapex article confirms the structure — six live, six neutral, six earth and a central pin — without giving the numbering.
- That audio multipin channel mappings are not standardised — the consistent finding across distributor and manufacturer documentation, stated plainly by Audio Accessories' own pinout page, which notes that pinout diagrams are suggestions and that the wiring varies with the equipment.
- Resistivity and the derived figures — copper at 1.724 × 10⁻⁸ Ω·m, 20 °C. Volt drop, damping factor and cable loss are computed from that and nothing else.
Assembled 7 September 2026 with AI assistance. The Socapex pinout is a mains wiring table and nothing on this page has been metered. It is validated at build time for internal consistency — six complete circuits, no pin used twice, earths contiguous and separated from the live pins — which catches a transcription error but cannot catch a wrong source. Three sources agree, and a fourth arrangement is claimed elsewhere. Before you build or trust a loom, meter it; before you work on mains, be qualified to.
Companion page: what is inside a four-channel CAT5 stagebox — the same "no standard, five conventions" problem, one cable size down.