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XLR Connectors

 

 

As the gap between consumer and professional equipment becomes blurred, we are beginning to see professional features on domestic camcorders.  One such feature is the use of XLR connectors for audio.  There are not many models on which this appears but as more professionals use small digital camcorders in ‘throw away’ situations like ENG, they may become even more common.

XLR connectors come in many different pin arrangements, but those used for audio usually have 3 pins in the male or female format.  Apart from being a very robust and reliable connector, the principle difference is that they are designed for balanced signals.  The standard audio signal in domestic equipment probably didn’t have a name until ‘balanced’ came along so now it is referred to as ‘unbalanced’
     
The unbalanced line uses two wires, one carries the signal whilst the other is connected to earth and is usually a braid around the outside of the signal to screen it.  It is often referred to as the screen.

The balanced line still uses an earth wire to provide an earth screen but it also uses two signal wires, one that is ‘In Phase’ and one that is ‘Out of Phase’  Rather than launch into a technical explanation, lets just say that this method is far more efficient against noise and interference, particularly in long runs.

This is all well and good if you are working exclusively with professional equipment but what happens when you want to use an existing microphone that is equipped with a 3.5mm jack plug.  Or, what if you purchase a new microphone and find that it is fitted with an XLR socket and you want to use it on a domestic camcorder with a 3.5mm jack socket.

Fortunately  XLR circuits are quite forgiving and it is usually possible to wire an ‘Unbalanced’ signal into a ‘Balanced’ connector or visa-versa.  XLR connectors use standard pin wiring and although the legend can be quite small, the pins are numbered and is the same for male or female connectors.  At the end of this article you will find details of how to cross wire connections.  If you wish to make them yourself, take my advise and buy the cable partially made.  For example, to achieve the example on the right I purchased a cable with 3.5mm Jack Plugs on each end and simply cut off one and replaced it with the XLR.
 

PLEASE NOTE that whilst the main theme of this article is concerned with wiring ‘Balanced’ to ‘Unbalanced’ lines, some consideration must be given to the relative impedance of each device.   I have carried out most of the modification successfully, but I can not guarantee that it will work for you.

TIP – XLR cables usually have a male connector at one end and a female at the other.  To determine which end goes where, remember that the signal travels in the same direction as the pins

 

Resources:-

Neutrik Connectors

Studio spares

Canford Audio

Maplin Electronics

    
   

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  UNBALANCED BALANCED  
  Pin 1 = Screen Pin 1 = Screen  
  Pin 2 = Signal Pin 2 = In Phase  
  Pin 3 = Screen Pin 3 = Out of Phase  

 

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