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Insight - How XLR Connector Works

Written By: 

Abhimanyu Mathur

Every year, technology sector companies invest millions of dollars in R&D to improve their products and release new products. An important part of these products is characterized by the connectors they use. For instance, a computer requires USB and PS2 Connector, a headphone requires TRS connector and a telephone requires RJ11 connector and so on. For high quality professional sounds, XLR connector is widely preferred. The term XLR derives its name from Cannon “X” series (where it was first used). Terms “L” and “R” are derived from latch and rubber used in the connector.

From a good microphone to a tuned guitar, all gadgets should be well matched up to the needs of the performer. Playing a critical role in professional audio applications is an XLR connector. Connecting the microphone to the amplifier, these connectors form an indispensible part of any electric instrument.
A 3 pin connector specifically designed for audio applications, XLR are known to be used in almost every wired microphone. Let’s get into the internal structure of the connector and discover various parts that make the connector function.
Fig. 1: Front View of 3-pin XLR Connector

Front Structure

Front Structure: The image above shows front view of a 3 pin XLR connector. The connector is made up of alloy (usually of zinc) and plastic.
There are three pins to take the input from the microphone. A small steel latch locks the microphone with the connector.
Fig. 2: Input Pins and Labels for Wire Combination
Input Pins: The inputs are labeled from 1 to 3 which aids in identifying the right pins when the wiring of the connector is done. In a professional sound system, inputs 1, 2 and 3 get the following wire combination:
·                     Input 1 for Ground
·                     Input 2 for Live
·                     Input 3 for Negative
Fig. 3: Image Indicating the Latch-Based Lock Mechanism of XLR Connector

Locking the device

Locking the device: It is very essential for any connector to connect tightly to its corresponding device. A latch based locking mechanism solves this purpose in a microphone.
The larger latch is accessible to the user while the smaller one hides under the device. A rubber ring protects the device from wear and tear.
In order to disconnect the device, the larger latch is pressed which in turn presses the smaller latch. The device can be then removed from the XLR connector.
Fig. 4: Rubber Ring of Connector
Rear View: The rear side of the connector is the output part from which the wire extends out. The blue colored plastic casing helps in griping the connector to connect or disconnect. The black rubber casing which is called the sleeve keeps the wire straight thereby  avoiding any mechanical damage to the connections.
Fig. 5: Image Showing Connection of Plastic Casing with Alloy Structure
The image above shows the connection of the plastic casing with the alloy structure.
Fig. 6: Layout of Alloy Structure Indicating the Bullet-like Projection at its End; Plastic Casing on Right

Wire Streamliner

Wire Streamliner: When separated, the alloy region has an inverted bullet like plastic coming out of its bottom. This part streamlines the wires inserted to connect to the pins of the connector.
Fig. 7: Image Showing Interface for Wires
Interface for Wires: The image above shows the pins of the connector where the wires are soldered.
Fig. 8: Lever for Latch Movement

Lever for Latch movement

Lever for Latch movement:  The latches placed on the connector for holding the device have a vertical back and forth movement because of a lever placed beneath them. This lever structure gets pressed whenever the device has to be disconnected and as soon as force gets off, it places the latches back in their rest state. Thus, having a spring like motion to assist latch movement is the prime function of the lever.
Fig. 9: Image Showing Mechanism for Holding Pins in Connector
Holding the input pins: The image above shows a small section through which the pins of the connector are held. The input pins are firmly held in the plastic mould which restrict their movement. The pins also have certain extensions that limit their movement beyond a certain limit.
Fig. 10 Image Showing Structure of XLR Pins

The connecting pins have a structure similar to a flute. An extension which restricts the movement inside plastic molding can be seen in the image above.