Auxiliary Sends   

The auxiliary send allows the signal to be split and sent independently to some other location such as a signal processor (reverb, delay, compressor) or even to another channel of the mixer.
An output from the mixer which is used to send (route) the signal to additional external processing or special monitoring.  individual input strips on the mixer will have several auxiliary send channels, each of which usually goes to a master auxiliary send fader before being sent out. The signal to an auxiliary send may be “prefader”, that is, independent of the input fader on the mixer or “postfader”, i.e. dependent on the level set by the input fader.
After processing the signal it is usually sent back to the mixer output section via the auxiliary returns.  
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