Editing Balanced audio (section)

==Connectors==
Three-pin [[XLR connector]]s and quarter-inch (¼" or 6.35{{nbsp}}mm) [[Phone connector (audio)|TRS phone connector]]s are commonly used for balanced audio interfaces. Many jacks are now designed to take either XLR or TRS phone plugs. Equipment intended for long-term installation sometimes uses [[Screw terminal|terminal strips]] or [[Euroblock]] connectors.
Some balanced headphone connections also use a [[Pentaconn]] 4.4{{nbsp}}mm [[TRRRS connector]].

<gallery>
Image:trsconnectors.jpg|2.5, 3.5 and 6.35{{nbsp}}mm TRS phone plugs
Image:Xlr-connectors.jpg|Three-pin XLR connectors, female on left and male on right
Image:XLR-phone jack combo connector.jpg|Three-pin XLR plus 6.35{{nbsp}}mm TRS phone hybrid jack.
</gallery>

With XLR connectors, pins 1, 2, and 3 are usually used for the shield (ideally connected to the chassis) and the two signal wires, respectively. (The phrase "ground, live, return", corresponding to "X, L, R", is often offered as a memory aid, although the second signal wire is not a "return" in the case of differential signaling)  On TRS phone plugs, the tip is signal/non-inverting, the ring is return/inverting, and the sleeve is chassis ground. 

If a [[stereophonic]] or other [[binaural recording|binaural]] signal is plugged into such a jack, one channel (usually the right) will be subtracted from the other (usually the left), leaving an unlistenable  L − R (left minus right) signal instead of normal [[Monaural|monophonic]] L + R (left plus right).  Reversing the [[Electrical polarity|polarity]] at any other point in a balanced audio system will also result in this effect at some point when it is later mixed-down with its other channel.

[[Telephone line]]s also carry audio through balanced circuitry, though this is generally now limited to the [[local loop]].  It is called this because the two wires form a balanced loop through which both sides of the [[telephone call]] travel. As telephones require DC power to operate and to allow simple on/off hook detection, extra circuitry was developed where one signal wire is fed from the exchange power bus, typically &minus;50 volts, and the other grounded, both via equal value inductors which have about 400 ohms DC resistance, to avoid short-circuiting the wanted AC signal and to maintain impedance balance.

[[Digital audio]] connections in professional environments are also frequently balanced, normally following the [[AES3]] (AES/EBU) standard. This uses XLR connectors and twisted-pair cable with 110-ohm impedance. By contrast, the coaxial [[S/PDIF]] interface commonly seen on consumer equipment is unbalanced.