Editing Balanced audio (section)

{{Short description|Method of interconnecting audio equipment}}
[[File:Noise rejection on balanced line.svg|thumb|upright=1.5|An audio signal transmitted over a balanced line. The signal is kept intact while the noise (which appears as a common-mode signal at the receiving end) is rejected perfectly.]]

'''Balanced audio''' is a method of interconnecting audio equipment using balanced interfaces.  This type of connection is very important in [[sound recording]] and production because it allows the use of long cables while reducing susceptibility to external noise caused by electromagnetic interference. The balanced interface guarantees that induced noise appears as [[Common-mode signal|common-mode]] voltages at the receiver which can be rejected by a differential device.

Balanced connections typically use shielded twisted-pair cable and three-conductor connectors. The connectors are usually three-pin [[XLR connector|XLR]] or {{convert|1/4|in|mm|2}} [[Phone connector (audio)|TRS phone]] connectors. When used in this manner, each cable carries one channel, therefore stereo audio (for example) would require two of them.

A common misconception is that balanced audio requires the signal source to [[Differential signalling|deliver equal waveforms of opposite polarity]] to the two signal conductors of the balanced line. However, many balanced devices actively drive only one side of the line, but do so at an [[electrical impedance|impedance]] that is equal to the impedance of the non-driven side of the line. This impedance balance permits the balanced line receiver (input stage of the next device) to reject common-mode signals introduced to the two conductors by electromagnetic coupling.