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.
But godliness with contentment is great GAIN
December 8, 2007
In addition to frequent mentions in the Bible, Gain is also a knob on the standard mixing console (also called Trim). You’ll also find a gain control on most amplifiers. For many guitar amplifiers, gain is the only form of volume control. But don’t let this confuse you, it is an input level and not necessarily an output. If it is your only volume knob, then yes, it directly affects the output volume. But on the standard mixing console, the gain works in relationship with the EQ and Fader to decide what the volume is for a given channel.
You need a gain control because different types of audio inputs have completely different volume levels. For example, your typical microphone produces a very weak signal and requires the gain to be turned up at least half way in order to be heard or even start to cause the meter to start registering. On the other hand, MP3 players can have a rather loud volume (depending on its volume knob) and needs to have a minimum amount of gain. (In fact, there’s usually a “Pad” button next to the gain to turn down these high level inputs even more).
There’s two ways to decide on how to set the gain level. I’m not in the position to say which is right or wrong, though I do have a preference. The audio engineer in charge at your particular ministry may have his or her own preference that you need to follow.
Option 1) Set the gain using the meters on the console. Fancier mixing consoles may have a meter above every channel so you can visually see the level of sound coming in to the channel. Other consoles require that you press the Solo or PFL button to see the input level on a meter in the center or right edge of the console. While visually monitoring the level on a channel, your goal is to get the gain high enough so that the meter is responding to more than just the first green light, but low enough so that it only peaks occasionally in the yellow. If you get into the red, the sound will distort. So make sure you test the channel at its loudest to verify that you have turned the gain down enough.
With this method, you end up with all the channels being about equal to each other. In other words, if you set the fader (the main output volume for a channel) to the same place for a microphone and guitar, they get amplified at about the same volume.
Option 2) Use the gain to set the volume you will generally have that channel at. Imagine you have two guitar players, one is playing the lead/melody parts, and the second is just doing rhythm. During the concert/worship, you’ll want the rhythm guitar to be quieter than the lead so it hides in the background and enhances the music. If you set the gain according to option 1, then you will have the fader for the lead guitar set to 80% or so, and the rhythm guitar set to about 55% output level. But you can also turn the gain down for the rhythm guitar and set the fader equal to that of the lead guitar. This way you can have both faders set to about 80%, but the balance you want between the two guitars is still there (because the gain is lower, the rhythm guitar will be quieter).
This method is particularly useful on the lower end boards that do not have a Mute option on the individual channels. When your only method of silencing a channel (instrument not in use, turning off a microphone, etc) is to turn the fader all the way down, then it is helpful to know that when you bring the channel back up, you can set it to the same volume level as every other channel, you don’t have to memorize the different output levels for different instruments.
Such a method does not provide as much benefit when you can mute the channel without losing your place (you can leave the fader up and simply tap the mute button to silence it), or when you can program scenes that automatically change volume levels based on preset mixes (odds are you won’t run into these types of consoles as a new volunteer).
As you gain experience (pun intended, sorry), you’ll likely find yourself in a balance between the two options and not necessarily strictly adhering to one method or the other. Using the LED meters is a great way to start when trying to figure out where to set the gain knob to. And as the rehearsal progresses, you can adjust the gain as you hear the differences between the instruments and their parts, or just fine tuning different singers with their own different energies.
Don’t forget: EQ also affects input level. If you get the gain set just right so it peaks in the yellow, but then turn up one of the frequency knobs, you may end up in the red after all. What’s EQ you ask? Hopefully I’ll get into that in a future post/chapter.
