The XLR plug is the standard for pro audio and video applications. The plug is actually an electrical connector by design. Not unlike the more ubiquitous RCA plug , which used regularly with home audio and video electronics, the XLR connector is different in several important ways.

Originally designed and manufactured by James h. the connector was first named the “Cannon X,” and after the addition of a latch the “Cannon XL” and finally the “XLR” after having a rubber compound added to the connectors.

The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections between equipment. Other configurations are also widely used including the 4-pin XLR4, for Clear-Com and Telex intercom headsets and DC power connection for film and video cameras. The XLR5 connector is the standard for DMX512 digital lighting control and also is used for dual element microphones and dual channel intercom headsets. XLR6 is the standard connection for dual channel intercom belt-packs.

There are several now obsolete configurations with additional pins including the XLR-LNE mains power connector, which was identified by its red insulation and shrouded pins, and has now been replace by the Neutrik PowerCon connector. XLR3 connectors were at one time also used extensively on 2-conductor loudspeaker cables, with either pin 2 or 3 as live (depending on the manufacturer) and pin 1 as the earthly return. However, this turned out to be dangerous to equipment and has since been replaced by the Neutrik Speakon connector.

XLRF connectors are made to connect the ground pin first, before the other pins make contact while the XLRM is being inserted. Due to the fact that the ground connection is made before the signal lines make contact, XLR’s can be plugged and unplugged without interference from external signals, a common problem with RCA connections. There is some discrepancy between various manufacturers between swapping pin 2 (normal input) and pin 3 (inverting input), but this reflects nothing more than their own pre-existing standards before any standards existed. Pin 1 is exclusivley the earthly return or ground pin, and often soldered to the internal shell or case.

Lastly, the XLRM male plug is used for output and the XLRF connector is used for input. So, vocal microphones for example will have the XLRM connector. Signal cables will have XLRM at one end and an XLRF connector at the other. Mixers and other multi-track recording equipment components will have XLRF inputs, and XLRM returns to stage, or out to other components.

XLR connectors are the standard in the professional audio and recording industry. XLR plugs are typically referred to as balanced and help reduce noise interference, especially over long spans. Quality in XLR cables varies greatly depending on the manufacturer, but for professional use please check out Canare, Mogami and Neutrik.

The most exciting development in recent years has been the advent of USB microphones which can connect directly to a MAC or PC. USB microphones are becoming increasingly popular as studio microphones, while live stage mics continue to use the standard XLR connectors.