Audio cables and connectors explained: XLR, TRS, TS, balanced vs unbalanced, and signal levels

Two cables can look identical and behave completely differently. A guitar lead and a balanced patch cable both end in a quarter-inch jack, but put the wrong one between your interface and your monitors and you may get hum, a weak signal, or nothing at all. This guide sorts out the connectors, what "balanced" really means, and the three signal levels you will meet in a home studio. Sources were read on 30 Oct 2026.

The connectors

XLR. The round, three-pin, latching connector on microphones and most mic inputs. The "L" refers to the latch that was added by 1950. Under the AES14-1992 convention, pin 1 is ground or shield, pin 2 is hot (positive polarity) and pin 3 is cold (negative); before that standard, some American makers wired pin 3 hot (XLR connector). XLR also carries phantom power, nominally 48 V, applied equally through the two signal lines.

TS (tip, sleeve). A jack with two contacts: one signal and one ground. Guitars, keyboards and electronic drum kits generally use 6.35 mm (1/4 in) TS plugs (Phone connector). TS is unbalanced.

TRS (tip, ring, sleeve). The same jack with a third contact, the ring. That one extra contact can do three different jobs:

• Balanced mono: tip and ring carry the two legs of one signal. This is how most interface line outputs and monitor inputs use it.
• Unbalanced stereo: tip is left, ring is right. Headphones and 3.5 mm (1/8 in) mini-jacks work this way.
• Insert send and return: tip send, ring return, on mixer insert points (Phone connector).

The plug cannot tell you which job a socket expects. The manual or the label beside the socket can.

Balanced vs unbalanced

An unbalanced cable has one signal wire and a ground, so any interference the cable picks up is simply added to your audio.

A balanced cable has two signal wires, twisted together inside a shield. Interference lands on both wires about equally, and the receiving input responds only to the difference between them, so that shared, "common-mode" noise cancels (Balanced audio). That is why balanced runs can be long, which is why microphones and PA amplifier feeds use them.

One detail most guides get wrong: a balanced line does not need the two wires to carry mirror-image signals. What matters is that both legs have equal impedance; plenty of gear drives only one side. Driving both sides in opposite polarity adds some headroom (about 6 dB), but it is not what rejects noise (Balanced audio).

The catch: balancing only works if both ends are balanced and the cable is TRS or XLR. A TS cable into a balanced output throws one leg away and leaves you with an ordinary unbalanced connection.

Mic, instrument and line level

"Level" is how strong the signal is, and each input is designed for one range.

• Mic level is the weakest. It needs a preamp to bring it up to line level (Line level).
• Instrument level comes from guitar and bass pickups. It is also weaker than line level and comes from a high-impedance source, which is why interfaces have a separate "Hi-Z" or "Inst" setting.
• Line level runs between interfaces, synths, outboard gear and monitors. Professional gear is nominally +4 dBu (about 1.228 V RMS); consumer gear is −10 dBV (about 0.316 V) (Line level). Feed −10 gear into a +4 input and it will sound quiet; go the other way and you risk clipping.

DI boxes bridge instrument and mic level. A DI takes a high-impedance, unbalanced signal and turns it into a low-impedance, balanced one that can run down a long cable to a mic input. Passive DIs use a transformer and need no power; active DIs have a preamp and need batteries, mains or phantom power. Many include a ground-lift switch for hum from ground loops (DI unit).

What we think: a five-line checklist

Our take is that cable problems in home studios are rarely about cable quality and almost always about cable type. Before buying anything expensive, check these:

1. Guitar or bass straight in? TS cable into an input switched to Inst/Hi-Z.
2. Interface to monitors? TRS-to-TRS or TRS-to-XLR, if both ends say "balanced". Hum through a TS lead here is the most common fix we see.
3. Synth or drum machine? Most use unbalanced line outs; a TS cable into a line input is fine for a short run. Keep it short and away from power bricks.
4. Long run to a stage or another room? Convert to balanced early with a DI and run XLR.
5. Hum that will not go away? Try the DI's ground lift before replacing cables, and never remove the safety earth from a mains plug.

Related reading: choosing an audio interface, recording guitar at home, phase and polarity explained (a pin-2/pin-3 swap is a polarity flip) and gain staging.