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Sound Mixers: Channel Assigning & Panning
One of the last sets of controls on each channel, usually just before the fader, is the channel assign and pan.
Almost all stereo mixers allow you to assign the amount of panning. This is a knob which goes from full left to full right. This is where the channel signal appears on the master mix (or across two subgroups if this is how the channel is assigned). If the knob is turned fully left, the channel audio will only come through the left speaker in the final mix. Turn the knob right to place the channel on the right side of the mix.
This option may be absent on smaller mixers but is quite important on large consoles. The assign buttons determine where the channel signal is sent.
In many situations the signal is simply sent to the main master output. In small mixers with no assign controls this happens automatically.
However you may not want a channel to be fed directly into the main mix. The most common alternative is to send the channel to a subgroup first. For example, you could send all the drum microphones to their own dedicated subgroup which is then sent to the main mix. This way, you can adjust the overall level of all the drums by adjusting the subgroup level.
In the example pictured right, the options are:
- Mix: The channel goes straight to the main stereo mix
- 1-2: The channel goes to subgroup 1 and/or 2. If the pan control is set fully left the channel goes only to subgroup 1, if the pan is set fully right the channel goes only to subgroup 2. If the pan is centered the channel goes to subgroups 1 and 2 equally.
- 3-4: The channel goes to subgroups 3 and/or 4, with the same conditions as above.
For stereo applications it is common to use subgroups in pairs to maintain stereo separation. For example, it is preferable to use two subgroups for the drums so you can pan the toms and cymbals from left to right.
You can assign the channel to any combination of the available options.
In some cases you may not want the channel to go to the main mix at all. For example, you may have a channel set up for communicating with the stage via an aux channel. In this case you don't assign the channel anywhere.
Sound Mixers: PFL
PFL means Pre-Fade Listen. It's function is to do exactly that — listen to the channel's audio at a point before the fader takes effect. The PFL button is usually located just above the channel fader. In the example on the right, it's the red button (the red LED lights when PFL is engaged).
Note: PFL is often pronounced "piffel".
When you press the PFL button, the main monitor output will stop monitoring anything else and the only audio will be the selected PFL channel(s). This does not affect the main output mix — just the sound you hear on the monitor bus. Note that all selected PFL channels will be monitored, so you can press as many PFL buttons as you like.
PFL also takes over the mixer's VU meters.
PFL is useful when setting the initial input gain of a channel, as it reflects the pre-fade level.
PFL vs Solo
PFL is similar to the solo button. There are two differences:
- PFL is pre-fader, solo is post-fader (i.e. the fader affects the solo level).
- PFL does not affect the master output but soloing a channel may do so (depending on the mixer).
Sound Mixers: Channel Faders
Each channel has it's own fader (slider) to adjust the volume of the channel's signal before it is sent to the next stage (subgroup or master mix).
A slider is a potentiometer, or variable resistor. This is a simple control which varies the amount of resistance and therefore the signal level. If you are able to look into the inside of your console you will see exactly how simple a fader is.
As a rule it is desirable to run the fader around the 0dB mark for optimum sound quality, although this will obviously vary a lot.
Remember that there are two ways to adjust a channel's level: The input gain and the output fader. Make sure the input gain provides a strong signal level to the channel without clipping and leave it at that level — use the fader for ongoing adjustments.