XLR & mini XLR connectors
(1 342)XLR connectors and their smaller counterparts, i.e. mini XLR connectors are a standard of connectors commonly used in professional audio and video equipment, as well as for stage lighting control and powering devices with a relatively low power. You can also come across a term “Cannon connectors”, derived from the name of the inventor. The main idea behind the design of these connectors was to ensure high resistance to weather conditions, mechanical damage and electromagnetic interference.
XLR connectors come in male and female versions. Both types are available with cable or panel mounting. In the case of audio equipment, the plug is usually of the female type, while the socket in the device is of the male type, although this is not a standard provided by all manufacturers. The connectors are designed in such a way, that the first electrical connection is the chassis ground (sometimes also called ground/shield/screen), and only then the signal pins. Thanks to this order, it is possible to plug in and unplug the plug from the socket of audio devices without generating additional noise and interference.
Standard XLR connectors have a round cross-section and may feature a different number of pins, usually from 3 to 7, although it is possible to come across XLR connectors with as many as 10 pins, and mini XLR connectors with up to 8 pins. While the design of XLR connectors is defined by the IEC 61076-2-103 standard, mini XLR connectors are not standardised under any norm.
XLR connectors – number of pins and their application
Currently, the most popular connectors in terms of the number of pins are those with three contacts. This is the industry standard for balanced audio signals. One of the pins is connected to the chassis ground, sometimes it is the ground itself. Then, it serves as a shield protecting the cable against interference. Sometimes it is internally connected to the plug or the socket housing. The second pin is the positive terminal, sometimes referred to as the hot terminal, while the third pin is the negative terminal of the balanced audio signal, sometimes referred to as the cold terminal. Signal balancing involves applying an in-phase signal to one of the conductors and a reversed-phase signal to the other conductor (180° phase shift). Thanks to that, the induced interference in the conductors is balanced one with another and, therefore, a very good quality of the transmitted signals is ensured, which in the case of audio equipment means obtaining a clear sound at the output. In fact, vast majority of professional microphones, a significant part of speakers, as well as stage lighting equipment use XLR3 connectors, and they are also used to charge batteries, usually with a rated voltage of 24V, 36V or 48V. They can work with cables with a cross-section of up to 14AWG and carry a current of 15A, although this information should always be checked in advance in the documentation of the connector.
Next in line are connectors such as XLR4 connectors with four pins. They are often used in headsets, where two of them are responsible for the mono headphone signal, and the other two for the unbalanced microphone signal, although they may also be used in balanced headsets. Then, for each of the two channels, left and right, there are two contacts, where each pair has a positive and a negative phase. They are also used in professional video and camera equipment, as well as some microphones that use LEDs to indicate that the device is properly powered up and on.
Five-pin Cannon connectors are used for DMX512 standard digital lighting control and in microphones that have two balanced audio signals and a common chassis ground, as well as in stereo headsets where three pins correspond to the left, right and ground channels and the other two to the unbalanced microphone signal. XLR5 connectors are also used as power connectors for various types of audio equipment.
Compared to XLR5, XLR6 connectors can operate in professional headsets with a balanced microphone signal and, like the previous versions, stage lighting control systems.
Together with the typical XLR connectors we can find hybrid connectors, which combine the XLR connector and the 6.3 mm Jack input. It is an answer to the wide and interchangeable use of these two standards in audio equipment. Thanks to them it is easy to connect devices that are not included in the set provided by the manufacturer and have different connectors.
This standard of connectors can be found in many variants of mechanical mounting, mainly in panel mounting, i.e. with a flange for two or four screws, with a flat or conical face, with a nut at the front or back, as twist-on connectors to which cables are soldered, but also with the THT mounting method, adapted to PCBs. As many other types of connectors, they come in straight spatial orientation, but also in the 90° degrees angular orientation, and their body can be made from metal or plastic. Apart from common XLR plugs and sockets, there are also connectors and patch panels adapted to installation in RACK standard cabinets.
XLR sockets and connectors – a summary
In summary, XLR connectors have many advantages, including high resistance to electromagnetic interference and noise when plugged into the socket. An additional advantage is the fact that they have a latch preventing spontaneous disconnection and ensuring correct electrical contact, as well as the possibility of applying signal balancing, which positively influences the quality of transmitted data, even in relatively long cables.
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