An aux-send (auxiliary send) is an electronic signal-routing output used on multi-channel sound mixing consoles used in recording and
broadcasting settings and on PA system amplifier-mixers used in music concerts.
The routing configuration and usage of an aux-send will vary depending on the application.
Two types of aux-sends commonly exists: Pre-fader and post-fader.
Pre-fade sends are not affected by the main slider for the channel, while post-fade ones are.
The benefit of using an aux-send is that it enables the signals from multiple channels on a mixing console to be simultaneously routed to
a single outboard device.
For instance, audio signals from all the channels of a sixteen channel mixing console can be routed to a single outboard reverb unit so that all channels are heard with reverb.
The aux-sends from a group of inputs can also be routed to an amplifier and then sent to monitor speakers so that the onstage musicians can hear their singing or playing.
The benefit of using the pre-fade aux-send function is that the volume of the vocals or
instruments in the monitor mix does not have to be the same as the "front-of-house" mix for the audience.
Musicians whose voice is barely or not even present in the "front-of-house" mix can have their sound clearly and loudly sent through a monitor speaker so that they can hear themselves singing and ensure that their pitch and timing is correct.