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XLR connector

The XLR connector is a rugged electrical connector design. XLR plugs and socketss are used in many electronic applications.

The name XLR originally comes from the Canon part number. It has become the standard name for these connectors, which are now made by many manufacturers apart from Canon. Historically it is no more correct than the names "Canon plug" or even "Cannon plug", which also continue to be used.

Patterns of XLR connector

The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections between equipment. The XLR5, with five smaller pins than the XLR3, is the standard connector for DMX digital lighting control.

Many other types exist, with various pin numbers. Most notable are two now obsolete 3-pin patterns manufactured by Canon. The power Canon had red insulation, and was intended as a mains power connector, but has been superseded by the IEC mains connector. The loudspeaker Canon had blue or white insulation (depending on its gender), was intended for connections between audio power amplifiers and loudspeakers, and was superseded in professional audio applications by the speakon connector developed by Neutrik.

XLR3 connectors

Left to right: Canon XLR3M line, Switchcraft XLR3F line, Neutrik XLR3M panel, Neutrik XLR3F panel

EIA Standard RS-297-A describes the use of the XLR3 for audio signal level applications. Some audio equipment manufacturers reverse the use of pin 2 (properly the normal input) and pin 3 (inverting input). This reflects their usage since before any standard existed. Pin 1 is always earth, and many connectors connect it internally to the connector body.

An XLR3M (male) connector is used for an output and an XLR3F (female) for an input. Thus a microphone will have a built-in XLR3M connector, and signal cables such as microphone cables will each have an XLR3F at one end and an XLR3M at the other. At the stage box end of a multicore cable, the inputs to the mixing desk will be XLR3F connectors, while the returns to the stage will be XLR3M connectors. Similarly, on a mixing desk, the microphone inputs will be XLR3F connectors, and any balanced outputs XLR3M connectors.

At one time XLR3 connectors were also used extensively on loudspeaker cables, as when first introduced they represented a new standard of ruggedness, and economic alternatives were not readily available. The convention was that a 2-conductor loudspeaker cable had XLR3F connectors on both ends, to distinguish it from a 3-conductor shielded signal level cable which has an XLR3F at one end and an XLR3M at the other. Either pin 2 or 3 was live, depending on the manufacturer, with pin 1 always the 'earthy' return. This usage is now both obsolete and dangerous to equipment but is still sometimes encountered, especially on older equipment. For example, some loudspeakers have a built-in XLR3M as an input connector.

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