The XLR connector (also called a Cannon plug or Cannon connector) is a type of electrical connector primarily used in professional audio, video, and stage lighting equipment. XLR connectors are cylindrical, with three to seven connector pins, and are often employed for analog balanced audio interconnections, AES3 digital audio, portable intercom, DMX512 lighting control, and for low-voltage power supply. XLR connectors are part of the international standard for dimensions, IEC 61076-2-103. The XLR connector resembles the DIN connector, but is larger, more robust and physically incompatible. The generic term XLR began as a trademark of Cannon Electric, with the letters standing for X model connector with an added latch (L) feature, and resilient (R) neoprene rubber surrounding the female contacts.
History and manufacturers
The XLR connector was invented by James H. Cannon, founder of the Cannon Electric company, Los Angeles, California. The XLR connector originated from the Cannon X series of connectors; by 1950, a latching mechanism was added to the connector, which produced the Cannon XL model of connector, and by 1955, the female connector featured synthetic-rubber insulation polychloroprene (neoprene), identified with the part-number prefix XLR. There was also the XLP series of connectors with hard plastic insulation, but the XLR model name is commonly used for all of the variants. Originally, the ITT Cannon company manufactured XLR connectors in two locations: Kanagawa, Japan, and Melbourne, Australia. The Australian factory was sold to Alcatel Components in 1992 and then acquired by Amphenol in 1998. Later, the Switchcraft corporation manufactured compatible connectors, followed by the Neutrik company, which made improvements to the connector, and produced a second-generation design (the X-series) that had only four parts for the cable connector, and eliminated the small screws used in the models of XLR connectors made by Cannon and Switchcraft, as well as in earlier Neutrik series.
Design XLR connectors are available in male and female versions in both cable and chassis mounting designs, a total of four styles. This is slightly unusual as many other connector designs omit one of the styles (typically a chassis mounting male connector). The female XLR connectors are designed with a longer metal sleeve to first connect pin 1 (the earth pin), before the other pins make contact, when a male XLR connector is inserted. With the ground connection established before the signal lines are connected, the insertion (and removal) of XLR connectors in live equipment is possible without hearing a static pop (as usually happens with, for example, RCA connectors). The number of pins varies. As of 2016, XLR connectors are available with up to 10 pins, and mini XLR connectors with up to eight. XLR connectors from different manufacturers will intermate, with the exception of six-pin models, which are available in two incompatible designs. The older Switchcraft six-pin design adds a center pin to the standard five-pin design, whereas the newer Neutrik design is a different pattern. The Switchcraft six-pin female will accept a standard five-pin male plug, whereas the Neutrik six-pin design will not. Neutrik offers connectors in both six-pin designs. The terminology for labeling the corresponding members of a pair of mating connectors follows the usual rules for the gender of connectors: a male connector is the one with pins on the smallest element, a female connector has corresponding receptacles. A plug connector enters the socket connector, judged by the largest element. For most other cable types, plugs are male, and sockets are female. XLR cables are unusual in that, at least in audio applications, all four combinations of male and female, plugs and sockets, are equally common. XLR connections often employ many free female connectors and panel-mounted male jacks. There is a loose convention for audio work that signals are generated by equipment with male pins and transmitted to those with female receptacles.
Current patterns and applications
Three-pin (XLR3) Three-pin XLR connectors are by far the most common style, and are an industry standard for balanced audio signals. The great majority of professional microphones use the XLR connector. In previous years, they were used to connect loudspeakers to their amplifiers, for instance by Trace Elliot in its bass enclosures. The XLR could accept 14 AWG (1.6 mm or 0.063 in) wire with a current-carrying capacity of 15 amps, suitable for most loudspeakers, but they have been superseded by the Speakon connector for professional loudspeakers. The Speakon connector accepts larger wire and carries more current, and it provides a better shield for the contacts, which may carry dangerous voltages when connected to an amplifier. Three-pin XLR connectors are used to interconnect powered speakers with line-level signals used for PA system applications. Rechargeable devices exist that use three-pin XLR connectors. These can be found on electric-powered mobility wheelchairs and scooters. The connectors carry from 2 to 10 amps at 24 volts. An obsolete use for three-pin XLR connectors was for MIDI data on some Octave-Plateau synthesizers, including the Voyetra-8. The three-pin XLR connector is commonly used for DMX512, on lighting and related control equipment, particularly at the budget / DJ end of the market. However, using three-pin XLR connectors for DMX512 is specifically prohibited by section 7.1.2 of the DMX512 standard. Use of the three-pin XLR in this context firstly presents a risk of damage to the lighting equipment should an audio cable carrying 48-volt phantom power be accidentally connected.
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