Audio Mixer Outputs Explained | Main, AUX, Matrix, & Direct Out

Written By Kyle Mathias  |  Audio Basics, Live Sound 

If you’re confused by all of the different output connections on your mixer, I’m here to help you in this post. 

We’re going to take a look at the common outputs you’ll find on a mixer and I’ll help you to understand when you might use each output by passing along a simple analogy that I found very useful when I was first getting started.

For a full mixer tutorial, check out this post: Audio Mixer Quick Start Guide

Main Outputs

The most common outputs you’ll find on almost any mixer are the main left and right outputs.

All of the input channels of the mixer can be routed to the main outputs using the input channel faders to determine the level of each channel. Typically, there will be a master fader or knob in the bottom right corner of the mixer that controls the level of the main outputs.

The main outputs can be used in a variety of ways, depending on what you’re doing.

In a live situation with one pair of main speakers, the main outputs can be used to send signals to those main speakers. They can also be used when recording several inputs and mixing them down into a stereo tape machine or audio interface.

There are really an infinite number of ways to use the main outputs – the most important thing to know is that they will usually reflect the signal passing through the master fader.

Direct Outputs

Let’s say you want to record several microphones to separate tracks in your DAW, so that you will have individual control of each instrument later on while mixing. Rather than using the main outputs, you’ll probably want to use the direct output for each channel.

The direct outputs will usually output the signal directly after the preamp. So, the signal from the direct output will be “dry”, meaning it isn’t affected by the EQ, compression, or other effects on the mixer. The channel fader also won’t affect the direct output.

This is a good solution if you want to run a live show using the mixer controls, while also preserving a clean recording of each input signal that can be mixed later on.

The only adjustments on the mixer that will affect the direct output signal is the preamp knob on each channel.

Aux Outputs

One of the most versatile types of outputs you’ll find on an audio console is the aux, or auxiliary output.

You can determine how much of each channel is routed to the auxiliary output using the aux send on each channel. Then, you can control the overall output level of the aux output using the aux master fader or knob.

You can think of an aux as a secondary main output. 

Some consoles allow you to select between pre-fader and post-fader. A pre-fader aux send won’t be affected by the position of the channel fader, while a post-fader aux send will.

One of the most common ways to use an auxiliary channel is for sending signals to stage monitors. Stage monitors are the speakers that point toward the musicians on stage, which enable the musicians to hear themselves and one another. If your console has 4 auxes, each one could feed the speaker in front of each musician. That way, you can send each input to each musician on stage at the level that suits their individual needs.

Another way to use an aux is for FX like reverb and delay. Rather than putting a reverb processor on every individual channel, you can connect one reverb to an aux output and connect the output of the reverb to an FX return channel. Now, you just need to send each channel to that aux with the aux sends. This allows you to have a cohesive reverb sound for every instrument while maintaining control over how much reverb is applied to each channel.

These are just two examples, but there are endless possibilities. Once you understand how an aux works, you’ll be ready to think outside the box and potentially use an aux creatively the next time an unexpected situation arises.

Matrix Outputs

Some more advanced mixers will have matrix outputs, which are a bit more difficult to understand at first.

When I was an intern at a live sound company, one of my mentors told me this analogy, which I found very helpful. He said, “Think of each input channel as a passenger. Each passenger can travel on a bus, like an auxiliary bus or a main mix bus.” He then told me to think of a matrix as a ferry that (in addition to carrying passengers) carries buses to their destination.

Thinking of it this way helped me understand the difference between an aux and a matrix. You can usually only send individual channels to an aux output. A matrix is helpful when you want to send several buses to a single output.

Let me give you an example of a situation where this might be helpful. Let’s say you’re mixing a live show that has several zones of speakers. You may have main speakers beside the stage, front fill speakers at the front of the stage, delay speakers midway through the audience, and some speakers in a VIP tent backstage.

You want the master fader to be routed to all of these speakers, but each speaker requires different EQ, level control, and delay time to maintain an even sound throughout all of the zones.

To do this, you could connect each zone of speakers to its own matrix output. This would allow the main mix bus to be a matrix input that could be routed to each zone.

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