Connectors and Cable Types, Identified

Every cable case in every venue holds the same argument: a tangle of leads that all look vaguely alike and are absolutely not interchangeable. The plugs are a code, and the code is worth reading, because the connector on the end of a cable tells you what the cable is for — what voltage it expects, whether it is shielded, and what happens if you press it into the wrong job.

This chapter is the identification guide. The theory of why balanced lines reject noise and what a DI box does lives in the cables lesson; this is the other half — walking up to a plug you half-recognise and knowing, before anything gets connected, what it carries and what it must never carry.

The Signal Connectors

• XLR (3-pin) — the professional audio default. Pin 1 is the shield, pin 2 is hot, pin 3 is cold; the connector locks, and the ground path mates before the signal pins do, so a live line can be plugged without a bang. Carries mic level, line level and — on many consoles — 48 volts of phantom power. Female end faces the source of the signal chain's listener: outputs are male, inputs are female, so signal flows from pins to holes.
• TRS (6.35 mm, two rings) — tip, ring, sleeve, and the most ambiguous plug in audio. The same connector serves a balanced mono line, an unbalanced stereo headphone feed, or a console insert send-and-return on one jack. Nothing on the plug tells you which; only the sockets at each end decide. Read the panel labelling before assuming.
• TS (6.35 mm, one ring gap) — tip and sleeve only: one conductor and a shield, unbalanced by construction. This is the instrument cable's plug. It also appears on unbalanced patch leads and, dangerously, on speaker leads — see the cable species below for why those two must never meet.
• 3.5 mm mini-jack — the TRS's small sibling, almost always an unbalanced stereo consumer connection: laptop headphone outs, playback feeds, in-ear packs. Treat anything arriving on a mini-jack as consumer level and unbalanced, and get it into a DI or a stereo line input early.
• RCA (phono) — unbalanced consumer connection at −10 dBV, the domestic operating level. DJ mixers, hi-fi gear and some playback devices. No lock, modest contact area, and a plug that connects signal before ground — expect a thump if you connect it hot.
• speakON — the round grey twist-lock, made for loudspeaker power. Two or four heavy contacts (NL2 and NL4), no exposed pins when unplugged, latches so it cannot be pulled out mid-show, and rated for tens of amps. If a cable has speakON ends, it is a speaker cable, full stop.
• banana plugs and binding posts — older amplifier outputs. Same job as speakON with none of the safety: exposed metal carrying amplifier power. Keep fingers off the posts while the amp is running.
• powerCON — speakON's blue and white cousin, and it carries mains electricity, not audio. Blue is power-in, white or grey is power-out. It is a locking connector, not a switch: it is not designed to be connected or separated under load, so kill the power before you touch it.
• etherCON — a locking, road-hardened RJ45. The cable is network cable; what it carries is whichever digital audio transport the gear speaks — a digital stage box's return, a console's remote link, a Dante network as the consoles lesson describes. It is data: no adapter turns it into an analogue signal.
• BNC — the small bayonet coax connector. In audio-land it almost always means word clock between digital devices, occasionally timecode or video sync. Never audio you can listen to.
• 5-pin DIN (MIDI) — instructions, not sound. A MIDI lead carries note and control data between keyboards, modules and controllers; plugging it anywhere analogue achieves nothing at all.

The Three Cable Species

Every analogue lead you will handle belongs to one of three constructions, and the construction — not the plug — is what makes them non-interchangeable.

• Microphone cable — two small twisted conductors inside a braided or served shield, XLR at each end. Built for low-level balanced signals and daily coiling. This is also what carries line-level balanced feeds; "mic cable" describes the construction, not the level.
• Instrument cable — one conductor inside a shield, TS plugs. Unbalanced, high impedance at the source end, and therefore length-limited: the cables lesson covers what every extra metre costs a passive pickup.
• Speaker cable — two heavy parallel conductors and no shield at all, because an amplifier's output is high-current and low-impedance enough that induced noise is irrelevant. What matters is resistance, so the conductors are thick: 1.5 mm² and up for real PA runs, heavier for long ones.

The classic failure is swapping the last two, because both can wear TS plugs and look identical from a metre away. An instrument cable on speaker duty puts amplifier current through a conductor sized for millivolts — it heats, wastes power in its own resistance, and can fail mid-show. A speaker cable on instrument duty hands an unshielded aerial to the highest-impedance, most noise-hungry source on the stage. Roll the plug in your fingers: a speaker lead is visibly fatter, stiffer, and shows two identical conductors if you can see into the plug. If a venue's cable case has unlabelled TS leads, that is a problem worth five minutes with tape and a marker.

Adapters, and the Ones That Lie

Adapters change the plug. They do not change the signal, and half the trouble they cause comes from hoping otherwise. An XLR-to-TS adapter does not unbalance a signal gracefully — it ties the cold leg to ground, which most (not all) outputs tolerate, and throws away the noise rejection you were paying for. A TS-to-XLR adapter does not make an instrument signal mic-shaped; the impedance is still wrong, which is the whole reason DI boxes exist. And a stereo mini-jack into two mono anythings needs an actual splitter cable wired for the job, not a barrel adapter.

The adapters worth carrying are the honest ones: XLR turnarounds (female-to-female, male-to-male), TRS-to-XLR both ways for balanced line connections, and RCA-to-TS for consumer playback into a DI. The one to refuse on sight is anything that adapts a speaker connection into a signal connection — that is an amplifier output looking for something to destroy.

What to Check Before the Next Load-In

• Read the plug before you trust the cable — speakON is speaker, powerCON is mains, XLR is balanced signal, and TS could be two very different things.
• Separate instrument and speaker leads for good — tape, colour, or a dedicated pocket; they must never be distinguishable only by memory.
• Assume every TRS jack is ambiguous — check the panel label for balanced, stereo or insert before patching.
• Get consumer sources balanced early — RCA and mini-jack feeds go into a DI at the source, not down thirty metres of unbalanced hope.
• Never separate powerCON or speaker connections under load — power off first; the connector locks precisely so that choice is deliberate.
• Carry honest adapters and refuse clever ones — anything that promises to convert between signal families is really just moving the problem somewhere less visible.