XLR Connector Pinout

XLR Connector Wiring

This is a connector that I have seen soldered incorrectly a lot. The XLR connector was developed by Cannon Electric and the term XLR came from the Cannon part number system. X was for the X series of connectors, L meant it had a latch to lock it into place and R stood for rubber gasket. The term was kleenexed if you will in the early 70's to just the XLR connector.

The XLR is made to handle a balanced audio signal. Pictured is a female XLR. Pin 2 is refered to as balanced positive, pin 3 balanced negative and pin 1 ground. By using balanced signal paths it is possible to eliminate adjacent noise from riding on top of the intended audio signal. Any outside noise is cancelled out when it comes to the balanced input of a mixer or amplifier. Only the original signal appears. Newer mixers have at times not been very good at cancelling this noise as newer designs do not use input transformers. Audio transformers are by far the best way to bring audio into a mixer but good wideband audio transformers are expensive so they get left out on most less expensive mixers. These mixers usually use a matched set of resistors to help cancel out the unwanted signal before entering the input amplifiers.

Looking at the end of a female XLR
Just remember pins 1 and 2 are swapped when looking at a Male XLR.

When you are ready to solder your mic cable to the connector you cut off the outer jacket and you will see the twisted pair inside of a shield. These wires can be a black and a white or a red and a black or whatever. All that is important when making up balanced audio lines is making sure that pins 2 and 3 from the female goes to pins 2 and 3 of the male using the twisted pair wires. For example, if pin 2 of the female XLR is the white wire then pin 2 of the male should also be connected to the white wire so polarity is kept correct. The pin 1 ground will be connected to the ground or drain wire that usually follows the foil or braided shield. Strange things can happen in your audio if this is not followed. Also if you are using an intercom system over these cables chances are it won't work as DC voltages will be in the wrong polarity to fire up your intercom beltpack.

I hope this has helped explain using and soldering the XLR connector. If you have any questions or additions to this explanation, please drop me a line or use the "Ask A Question" button above. N8HKI

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