The XLR connector is a style of electrical connector, primarily found on professional
audio, video, and stage lighting equipment. The connectors are circular in design and
have between 3 and 7 pins. They are most commonly associated with balanced audio interconnection,
including AES3 digital audio, but are also used for lighting control, low-voltage power
supplies, and other applications. XLR connectors are available from a number of manufacturers
and are covered by an international standard for dimensions, IEC 61076-2-103. They are
superficially similar to the older and smaller DIN connector range, but are not physically
compatible with them.
History and manufacturers
The XLR connector was invented by James H. Cannon, founder of Cannon Electric in Los
Angeles, California, and for this reason it was sometimes colloquially known as a Cannon
plug or Cannon connector and in Japan as Cannon jack, though this term has since fallen out
of common usage in the industry. Originally manufactured as the Cannon X series, subsequent
versions added a locking mechanism and then surrounded the female contacts with rubber
polychloroprene insulation, which extended the part number prefix to XLR. There was also
an XLP series which used a hard plastic insulation, but was otherwise the same. ITT Cannon originally
manufactured XLR connectors in two locations Kanagawa, Japan and Melbourne, Australia.
The Australian operation was sold to Alcatel Components in 1992 and then acquired by Amphenol
in 1998. ITT Cannon continue to manufacture XLR connectors in Japan.
The Switchcraft corporation later started manufacturing compatible connectors, followed
by Neutrik. Neutrik made a number of improvements to the connector and their second-generation
design had just four parts for the cable connector and eliminated the small screws used by both
Cannon and Switchcraft, which were prone to working loose, falling out, and becoming lost.
These improvements made Neutrik the most popular brand of XLR connector.
Unbranded XLRs are also made by far-east manufacturers. Originally these were copies of the Cannon
or Switchcraft designs, but in recent years the Neutrik designs have also been copied.
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.
The female XLR connectors are designed to first connect pin 1, 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 of XLR connectors in live equipment
is possible without picking up external signals. The number of pins varies from three to seven.
XLR connectors from different manufacturers will intermate, with the exception of Switchcraft
6 pin models, which use a non-standard arrangement for the pins.
Current patterns and applications Three pin
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 for loudspeaker connections, for instance by Trace Elliot
in its bass enclosures. The XLR could accept 14 AWG 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. This use is commonly seen in PA system applications
and seems to be growing more common. 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. Four pin
Four pin XLR connectors are used in a variety of applications.
They are the standard connector for intercom headsets, such as systems made by ClearCom
and Telex. Two pins are used for the mono headphone signal and two pins for the unbalanced
microphone signal. Another common use is for DC power connections
for professional film and video cameras and related equipment. Some desk microphones with
LEDs use them. The fourth pin is used to power the LED indicating that the microphone is
on. Other uses for the four pin XLR include some scrollers, AMX analog lighting control
and some pyrotechnic equipment. Five pin
Five pin XLR connectors are the standard for DMX512 digital lighting control.
Other common uses are for dual-element or stereo microphones and stereo intercom headset.
Six pin Six pin XLR connectors are used for dual channel
intercom systems, and stage lighting control applications.
Seven pin Seven pin XLR connectors are used to connect
some valve condenser microphones to their power supplies.
Used by several models of Le Maitre and Ultratec fog machines for remote control.
An obsolete use for seven pin XLR connectors was analogue lighting control signals, as
well as for wired intercom in broadcast studios, specifically with Ward-Beck intercoms.
PDN The loudspeaker Cannon had blue or white insulation,
was intended for connections between audio power amplifiers and loudspeakers. These are
manufactured by Amphenol. Obsolete patterns
Many other types of connectors using the XLR type shell exist, with various pin configurations.
Most notable are two now obsolete three-pin patterns manufactured by ITT Cannon.
The power Cannon had shrouded pins and red insulation, it was intended as a mains power
plug, but has been superseded by the IEC 60320 series of connectors and increasingly, more
recently, the PowerCon connector developed by Neutrik.
Two pin Two pin XLR connectors were used in the 12V
DC power supply connection of Yamaha CP-series Electric Grand pianos.
Technical usage information This section contains more technical information
relating the most common applications of XLR connectors.
Three pin - audio
EIA Standard RS-297-A describes the use of the XLR3 for balanced audio signal level applications:
Prior to the introduction of this standard, the wiring of pins 2 and 3 varied. The pin
2 "hot" and pin 3 "cold" convention was typically used by European and Japanese equipment manufacturers,
but American companies used pin 3 "hot" and pin 2 "cold". This caused problems when interconnecting
equipment with unbalanced connections. The pin 3 "hot" convention is now obsolete but
is still found on vintage equipment. Pin 1 has always been ground and/or shield if the
cable is shielded, and many connectors connect it internally to the connector shell or case.
Although covered in industry technical standards, there is still some disagreement on the best
way to handle the use of pin 1 for grounding. The main controversy is whether the shell
of the connector should be connected to pin 1 or the shield, or left floating. AES standards
mentioned above recommend that shells of cable-mounted connectors should never be connected to pin
1 or the shield, because inadvertent contact of the shell with another grounded surface
while in use can create unwanted current paths for fault current, potentially causing hum
and other noise. On the other hand, equipment containing active circuitry should always
have pin 1 connected to the conductive enclosure of the equipment as close as possible to the
point where the signal enters the enclosure. The argument centers on the radio frequency
shielding provided by the shell of the connector, which may be reduced if it is left floating.
An alternative solution is to connect the shell to pin 1 and the shield through a small
value capacitor, providing RF shielding but allowing very little audio-frequency current
to flow. This capability can be built into a fixed jack or a cable terminated with XLR
connectors. The standard signal flow for audio in XLR
connectors is that the output is a male connector and the input is female. In other words, the
pins on the plug point in the direction of signal flow. This is the opposite of power
connector standards which normally use female connectors for outputs, a convention influenced
by the need to prevent accidental contact with dangerous voltages. However, the voltages
of microphone and line level audio signals are not hazardous. The male XLR is usually
incorporated in the body of a microphone. Since equipment often requires an input on
a TRS phone jack or an XLR connector, Neutrik and Amphenol offer several models of combination
connector that accept both XLR and 0.25 inch TS or TRS phone plugs.
Three pin - power The 3-pin XLR is used as a low voltage power
connector. Four pin - DC power
The most common standard is for pin 1 to be ground and pin 4 to be 12 volts, with pins
2 and 3 unused. This configuration is used on most professional video cameras and is
also common on audio equipment designed for location use. There are other non-standard
arrangements, particularly found on older equipment.
Four pin - intercom headset Clear-Com, Telex, RTS and many other production
intercom systems use 4-pin XLR connectors for attaching monaural intercom headsets or
handsets. The standard pinout for 4-pin XLR headsets is: Pin 1 = Microphone ground; Pin
2 = Microphone signal input; Pin 3 = Headphone ground; Pin 4 = Headphone signal output.
Five pin - DMX512 The 5 pin XLR is the standard connector for
DMX512, the most common protocol for controlling professional lighting and related equipment.
3 pin XLR connectors are increasingly common instead. These are electrically compatible
with a simple jumpering 1–1, 2–2, 3–3 between them.
Additional usage information 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 two-conductor loudspeaker cable had XLR3 female connectors on both ends, to distinguish
it from a three-conductor shielded signal level cable, which has an XLR3 female at one
end and an XLR3 male 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. This use was superseded
in professional audio applications by the Neutrik Speakon connector.
Phantom power
Some microphones such as condenser microphones require power. An alternative to battery power
is phantom power, which consists of direct current applied equally through the two signal
lines of a balanced audio connector, usually an XLR connector. The supply voltage is referenced
to the ground pin of the connector, which normally is connected to the cable shield
or a ground wire in the cable or both. Phantom power is usually supplied at a nominal 48
volts DC, although lower voltages are permissible. It is common for modern mixers to have a built-in
switch-operated 48-volt power supply which supplies all mic inputs with phantom power,
thus eliminating the need for bulky external supplies on individual mics.
XLD keyed variant The XLD connector is a proposed keyed variant
of the XLR connector. The keys prevent accidental mixing of XLR and XLD connectors. XLD plugs
and sockets are used mostly in professional audio and video electronics cabling applications.
The XLD connector is proposed by the Audio Engineering Society AES42 digital microphone
interface standard. The connectors are similar to XLR but with
an extra coding key and groove that allows control over the intermating of XLD plugs
and XLR sockets. A connector with the coding key installed will not mate with a connector
that does not have the matching groove. By suitably keying connectors, analog microphones
can be protected from damage by the high current digital phantom power supply provided for
digital microphones. See also
RF connector References
External links Making XLR cables