Aux Controls: Virtually all mixers have at least 1 “Aux” pot. Many have 4 to 8 of them. Some have even more. So what is “Aux”?
Aux stands for Auxiliary Output. The Aux Control is typically where you will output to monitor speakers on the stage, send a signal to an effects processor or perhaps a send to the “Fellowship Hall”. If you were recording, you might be sending to a channel on a tape machine. In short, the volume controls here allow you to send a different mix to any kind of output source that you define. For the sake of our discussion here, we will stick to Aux sends as Monitor sends (at least for the first part of this lesson).
In the channel strip at the right, you can see that we have 4 pots to control 6 Aux sends. Most boards will typically have anywhere from 2 to 8 Aux Controls. In our case at the left, the first two pots (Aux 1 and Aux 2) have a “pre” switch next to them.
The “pre” switch changes the sends to be either “Pre-Fader” or “Post-Fader”. The fader is the sliding volume control at the bottom of the channel strip. If we set the Aux sends to be “Pre-Fader” then the volume level that is going to the Aux output is going to stay the same no matter what we do to the channel volume fader. If we set the Aux sends to be “Post-Fader”, then if we turn up the volume fader at the bottom of the channel strip, we will also turn up the volume in the Aux output channel.
Why would we want use either “Pre-Fader” or “Post-Fader”?
Pre-Fader is used for things like monitors. For example, lets say we have a volume level set on stage for a monitor. As we listen to the mix back at the board, we decide that we need to have more volume of the particular instrument in the house sound. So, we turn up the slider at the bottom of the channel strip. Do we want the level of the monitor to increase just because we needed to hear more of that instrument out front? Nope. We already set the level that we want the instrument in the mix. So we would want that Aux send to be “Pre-Fader”.
Post-Fader is often used for effects. So, let’s say that we have an Aux send that is going to a reverb unit. The Reverb is adding some echo to give the sound some depth. Again, while we are listening to the mix, we decide that we need to increase the volume level of the instrument, so we push up the slider at the bottom of the channel strip. We increase the amount of “Dry” signal (“Dry” refers to a signal that does not have any reverb on it) to the mains, and we also want to increase the amount “Wet” signal to the mains so that the reverb doesn’t get overwhelmed by the “dry” signal. In that case, we want to set the Aux send to be “Post-Fader”.
Note that Aux 3-6 do not have a button for “Pre”. These sends are set to always be either “Pre-Fader” or “Post-Fader”. Check your mixer documentation so that you know. As you can see above, it can have a major effect on what you use them for.
However, you can see that on the channel strip, there is a button that says “5/6 Shift”. This particular mixer has 6 Aux outputs, but only 4 of them can be used on any one channel. Therefore, the button is used to switch between having the channel potentially send signals to Aux1-4 or Aux1, Aux2, Aux5 and Aux6. This allows the mixer manufacturer to save a little money on “pots”.
So, once you have determined what the Aux Controls will be used for, you can set the volume level of each individual instrument/mic for each Aux output. For the sake of this lesson, I will decide that I am going to use Aux 1 for the “Front Monitors” that the Singers hear and Aux 2 for the monitors for the Band. Then, I will probably mix the singers a little heavier in Aux 1 and the instruments a little heavier in Aux 2. Then, I am going to hook up a reverb unit to Aux 3. I will only use this for the Vocals because I don’t want to add the reverb to the instruments (for some reason). So then, I will make sure that I have Aux 3 turned down for all of the instrument channels and mixed appropriately for the mic channels.
Go to Lesson 4: EQ Controls