If you’re following along at home, we’ve discussed how the GAIN control works to control the input level into the mixing console. When you plug in that guitar, microphone, mp3 player, etc, that signal goes into one of the many input jacks on the back of the console, gets amplified or softened by the gain control, and then goes to the EQ controls. The EQ knobs also amplify or soften the signal, but it does so only at selective frequencies. (More on this someday)
After the EQ, the signal splits and goes to a couple of different places. The most obvious is the main volume fader, the big control closest to you that slides up and down. Though there may be rare exceptions, this is generally used to control the main volume in the house speakers. At the same time, the signal is also going to anything that is marked “PFL”, which stands for “Pre-Fade Listen”. Pre-fade, as in “the signal before it is affected by the main volume fader.” These are additional outputs on the board that have their own volume control and are not affected by what volume you set on the fader. The easiest one to spot is the button labeled PFL that usually appears above each fader. Mackie and some other brands call this SOLO, but it is the same thing. Pressing this button takes the signal from that channel and sends it to the headphone/control room output of the board. Because it is pre-fade, you can listen to that channel in the headphones even if the volume is turned all the way down. The gain will still have an impact on the volume you hear on pre-fade outputs, but the main fader will not.
In addition to the PFL headphone output, there are also a number of pre-fade auxiliary (AUX) outputs on the console. The Aux controls on the mixing console are basically separate volume controls for different outputs. Your primary fader will control the house speakers. The Aux controls will control everything else from monitors and in-ears for the band to hear themselves, recording outputs, effects units, etc. There are two types of aux controls on the typical board, and they are labeled as Pre or Post, or they have a button to press to switch between the two options. The “Pre” controls are outputs that ignore the fader volume you set. The “Post” controls are post-fade, their output volume is in direct relationship to the main fader. For example, if you have your volume turned all the way down so you don’t hear anything, any monitors on pre-fade may still be making noise, the post fade outputs will be silent. As you turn up the fader and begin to hear the music in the main speakers, so too will you hear them in the post-fade monitors. The pre-fade monitors will stay at the same volume regardless.
The average mixer (in my experience) has 6 aux outputs. I’ve worked with some that only have 1, and some high-end consoles that have 16, and some digital consoles with far more. But 6 is the most common, and is likely what you will be working with at an entry level position. Typically the Aux 1 and 2 controls are pre-fade, 5 and 6 are post, and the middle controls have a button to switch between the two modes. The more expensive boards may have buttons on 1 through 4, or possibly all 6 controls. The point is, you may have a choice about when to use a pre-fade or post-fade output. There is no simple definition about which to choose. Most aux controls are used for the band to control monitors and everyone may have a different opinion on whether to be pre or post-fade.
The second most common use for auxiliaries is effects. Reverb is the most common effects unit you’ll find in the typical setup. The shortest description of a reverb unit is that it takes a singers voice and makes them sound like they are in a bathroom. Done right, this is a good thing, that’s why your own voice tends to sound better in the shower. In order for it to work, you have to send the singers voice to the unit and then have the echo effect get put back into the mix. This is where the post-fade aux works best. Turn up the aux for a given singer until you have just enough of the effect to sound good (subtle is good!), and as you turn up or down the volume on that singer, the effect will change as well. The effects processor’s output will likely have its own input on the board, or the console will have a set of controls labeled “Return” that are used to put the echo or whatever effect back into the house and/or monitor mix.
This is just an introduction to the AUX controls and the idea of pre and post fade levels. In upcoming posts I will go into more detail about mixing the monitors and useful information for making the most out of an effects processor.
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