When beginning your sound check,use as much amplification from this stage as you can!!!
Most mixers have a knob called TRIM ,GAIN, INPUT LEVEL, PAD, or
INPUT ATTENUATION. We'll use the term GAIN to refer to the general function. Regardless
of the label such knobs all do about the same thing.

For example, turning up the gain maybe the same as reducing the pad. Be sure you know which
way to turn the knob to make the level higher. If you can turn this knob first so that there
is maximum gain (minimum attenuation) before adjusting any of the other controls on your
console, the mix will be quieter.

The more gain you get from the mic preamp, the less you will need to add from the other amps
in your console. Of course if the incoming signal from the microphone is already high in level
you need not turn up the GAIN all the way. Since you have more signal prior to preamplification,
You need less amplification overall from your console, and the output noise should go down.
Here is a suggested method for arriving at the correct setting.

STEP 1

To set the GAIN, first turn it down all the way. On most consoles, this means full counterclockwise
rotation. Make sure that any PAD or ATTENUATOR switch is NOT engaged.

STEP 2

Set the channels slide fader almost all the way up to the top of it's travel. Some consoles have
a heavier line, arrow or some other mark on the slider scale that can be used as a normal or
nominal setting for this procedure.

STEP 3

Set the submaster faders (if any) and the master faders to the same almost to the top position,
or to the manufacturer's mark.

STEP 4

Now, turn up the GAIN as high as necessary until the VU meters indicate the desired level
(typically peaking around zero, or 2/3rds of full scale). This formal procedure ensures that
you have, in fact, taken as much power from the microphone as possible before using amplification
from another part of the console.

If you followed these steps & the sound is fuzzy or distorted, it means that the source input
is too high. Turn down the amp or have the vocalist back away from the mic a little. Make the
adjustments then follow the steps again.

Information obtained from, THE YAMAHA SOUND REINFORCEMENT HANDBOOK - (written for Yamaha by Gary Davis & Ralph Jones-© 1990)