Aux-send

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 signal from the auxiliary send is often routed through outboard audio processing effects units (e.g., reverb) and then returned to the mixer using an auxiliary return input jack, thus creating an effects loop. This allows effects to be added to an audio source or channel within the mixing console.

Purpose

The routing configuration and usage of an aux-send will vary depending on the application.

Two types of aux-sends commonly exist: Pre-fader and post-fader. Pre-fade sends are not affected by the main slider for the channel, while post-fade ones are.

In a common configuration, a post-fade aux-send output is connected to the audio input of an outboard audio effects unit (most commonly a temporal effect such as reverb or delay [compressors and other dynamic processors would normally be on an insert instead]). The audio output of the outboard unit is then connected to the aux-return input on the mixing console (if the recording console has one) or as an alternative it can be looped back to one of the input channels on the mixing console. Mixing consoles most commonly have a group of aux-send knobs in each channel strip, where one knob corresponds to each aux-send on the board. The controls enable the operator to adjust the amount of signal that will be sent from its corresponding channel into the signal bus routed to its corresponding aux-send output. The reason that a post-fade is used is to avoid channels than are zero gain on the sliders from contaminating the effects return loop.