The INPUTS or channels strips
are available in both MONO and STEREO configurations. It is important to
consider this when evaluating a console for your particular application.
MONO inputs accept either a mic or line level input and the fader controls
a single signal. Many consoles feature a number of STEREO inputs, which
accept only line level inputs and control two channel inputs from a single
fader. Don't automatically assume that a 32-channel console offers 32 microphone
inputs when often several channels are reserved for line level devices
such as CD players, DAT machines, etc.

The Input or Signal Trim
is usually the first knob at the top of the channel strip; this level control
allows you to adjust the level of the incoming signal from a microphone
or instrument. Proper adjustment of this control maximizes the signal to
noise ratio of the signal. All sources put out different amounts of signal.
Some may be weak and others quite strong. If there is too much, distortion
will result. On the other hand, if there is too little, the channel level
may have to be set much higher than the rest of the channels. The input
is usually adjusted in conjunction with an LED Clip indicator or VU Meter,
which is used for setting the Gain/Trim/Pad. This LED is designed to illuminate
when the input signal is approaching the upper limit of the input circuit's
capacity, but still leaving around 3dB of headroom in most cases (check
the manual to be sure). It is thus possible to set the Gain controls simply
by watching the channel Clip indicators during a sound check and adjusting
them for slight amounts of activity. 

Aux Sends are simply what
the name implies, an auxiliary send of the audio signal or source input
for that channel strip. On mixers with "Pre/Post" EQ selector buttons for
these controls, they will come after the EQ section, otherwise they will
be right after the Gain, Trim, etc. This extremely versatile "knob set:
allows you to route the channel signal to an outboard effects processor,
recording device, assistive listening or broadcast output. Additionally
Aux Sends are often used to provide a separate mix for the stage monitors.
The reason for there being more than one Aux Send control on the channel
and more than one Aux Master Control is so that you can mix for more than
one monitor system. The drummer, for example, usually needs to hear himself
and the vocals extra loudly, and the vocalists, of course, need to hear
themselves very loudly while the guitarist might want to hear a predominance
of bass and keyboards because his amp is almost all he can hear.

The EQ or Equalizer section
usually follows the Aux Sends and is usually desirable only on that portion
of the channel signal headed for the FOH system. 

For example, stage monitors
operate in a terribly demanding acoustic environment - speakers are close
to mics and everything tends to be very loud. As a result, the best way
to mix for monitors is to treat them as a totally independent system. Large
concert PA's usually have a separate monitor mixer and someone to run it.
Smaller systems still need to treat the monitor mix as separately from
the main mix as possible. That is why the channel signals would not, as
a rule, be EQ'd before being sent to the Mon/Aux busses. That way, the
only equalization they get will be specifically for the stage monitor system.

For that reason, some mixers
have Aux Send controls after the EQ with "Pre/Post" selector buttons to
put the desired ones through the channel EQ ("Post") or to bypass it ("Pre").
In other mixers, one or more of the Mon/Aux controls may simply be after
the EQ (i.e. "post EQ") and are therefore permanently affected by it. 

All EQ's function by altering
the gain above or below normal over various frequency ranges. Some mixers
offer "semi-parametric" EQ. This usually comes in the form of one or more
cut/boost controls, each with a frequency control to position the cut/boost
exactly where you want it along the frequency spectrum. One application
of such a feature is in the fight against feedback. Here you would turn
the cut/boost control counter-clockwise to produce a "dip" in the frequency
response, then rotate the frequency control until the dip reaches the guilty
frequency and the feedback is reduced. 

The SWEEP control determines
what range of frequencies is affected by the MID cut/boost. It moves or
"sweeps" the MID control's peak or notch in response all the way up to
several thousand Hz or down to below one hundred Hz. As a result it can
have quite a noticeable effect on the sound especially since the MID cut
or boost will be interacting with whatever cuts or boosts you may have
set with the LOW or HIGH EQ controls. If you have set a LOW boost, a MID
boost swept all the way down to the lowest frequency setting will alter
the sound of lows AND increase their volume. As music plays through a channel
on the mixer and speakers, adjust that channel's MID, first for a boost
then for a cut and SWEEP them back and forth. (If there is no MID cut or
boost setting, i.e. if it is set at the center position, the SWEEP will
have no effect at all). Now repeat the process with that channel's LOW
and HIGH EQ controls at various settings (but with the volume at a safe
level for the speakers). 

Most EQ sections include
an optional High Pass Filter, which inserts a Low Frequency Cut at a pre-selected
frequency usually at or near 80Hz. By invoking the HPF you automatically
attenuate these lower frequencies. This feature can be very useful in cleaning
up the mix by removing ambient low frequencies from open vocal mics.

The Pan control found only
on mixers with stereo Main outputs, functions a bit like the "balance"
control on a home stereo system. In fact it regulates how much of the channel's
post-EQ signal gets routed to either the Left or Right Main PA busses.
If, for example, the Pan control is rotated all the way left, that channel's
signal will only go to the left Main buss. If the F.O.H. (main) PA is stereo,
only the speakers on the left side of the stage will be producing that
channel's output - not an ideal situation. In most PA situations, the only
real reason for running a stereo F.O.H. system is to get the sonic benefit
of a stereo reverb. However, if you have a basic stereo mixer with a "Main"
master and corresponding mono output, and you are running a mono F.O.H.
system, the PAN controls can be used to establish two main mixdowns, perhaps
one for the live sound and the other for recording.

The Pre-Fade Listen or PFL/Cue
button sends post-EQ channel signal to the headphone amplifier so those
individual channels can be isolated through the phones. Because the PFL/Cue
signal is tapped off just before the channel fader (hence "pre-fade") you
can shut that channel down through the FOH PA, but still hear it through
your headphones. This is a convenient feature for previewing channels before
bringing them into the mix (eg., for cueing tapes up). It may also be used
for checking out problems - a squealing amp, a distorted mic, etc. 

The Mute button is usually
inserted just after the EQ section. I mention it at the end of the channel
section simply because that is where the button most often appears - i.e.
conveniently close to the channel fader and PFL/Cue button. As the name
implies it silences the channel through the FOH system and possibly the
monitors (check your manual). Its prime function is to enable the user
to pre-set a channel's level, then shut the channel off to be added to
the music program later on. Muting is a convenient feature for infrequently-used
channels such as harmonica mic, acoustic guitar, banjo, mandolin, certain
wind and percussion instruments, pre-recorded music or sound effects, all
of which should be left off when not in use to reduce unwanted sound pickup
and the risk of feedback. 

And finally the Fader or
level control is the slide control that allows you to adjust the amount
of signal that appears ion the main mix. While the trim control is used
to adjust all of the incoming signal levels to be nearly the same, the
fader allows you to adjust the relative levels of each channel being mixed
to the master mix buss. Usually adjacent to the channel fader, are the
Submix sends, which allow you to assign the channel strips to the master
subgroup faders. For example you may wish to assign all of the drums and
percussion to one group and the background vocals to another. This method
of mixing enables you to control the relative levels of groups of microphones
with just one fader in the master or control section.

The features of the master
or Control section of the mixing console generally act as output level
controls for their designated output connectors, one exception being the
Aux Return master(s) since those jacks are inputs. Aside from that, everything
does exactly what its name implies. Check the owners manual for your specific
console for more detailed information on any of these features. 

The Sub Group masters regulate
the Sub mix or Group output levels, which are assigned by each channel
strip. When a console is properly adjusted it is possible to mix entirely
from the Sub Group faders which each control entire groups of input channels.
The Main output(s) regulates the output of the MAIN, SUM or MONO buss where
the outputs of the Sub or Group busses or Left & Right stereo master
busses get mixed down into a single signal which is delivered to the amplification
system.

The Aux Send masters regulate
the output level of all of the channel strips, which are sending signal
via the Aux Send. This control is used to set the output level of the signal
being delivered to effects processors, recording devices, etc. The Aux
Return masters regulate the input levels of their designated RETURN jacks
such as the signal being returned from an effects processor. The effects
return offers a convenient method to blend the level of the effects device
back into the main mix. 

A mixer may have 12, 24,
36 or upward of 56 channel strips. That's a lot of knobs! But remember
that most channel strips are exactly alike, and once you learn the features
and operation for a single channel strip. Therefore you can simply repeat
the process for the input, aux send and eq for each channel strip, bearing
in mind that each instrument or vocal will require it's own unique adjustments.

One of the best ways to become
familiar with a console is to spend a some time in practice. First, you'll
need a sound source, or a selection of sound sources. There are two types
of sources you could use: one is an acoustic source picked up by a microphone;
the other is a direct source, such as tape or CD. I suggest you begin by
using a tape or CD player, connected to a line input of your mixer.You'll
also need decent headphones or some good quality studio monitors connected
to the control room or main mixer outputs. By monitoring the console output
as directly as possible, you will be able to hear qualitative changes as
you make them - including subtle differences room acoustics or ambient
noise would otherwise obscure.

The idea is to send your
program source through an input channel, play with the various channel
controls (EQ, pan, etc.), and monitor the results. You may want to connect
your source to a stereo channel to do some of your tests and then connect
to a mono input to discover the differences. The stereo and mono inputs
may differ, for example, in the EQ control available. Also, listen to how
the pan (or balance) control differs on a stereo channel from the pan on
a mono channel.

The area you'll want to spend
the most time with is the EQ. Listen to a variety of program material to
determine how your mixer's channel EQ affects the sound of the signal.
Some of the best recordings to use include male speaking voices and solo
recordings of piano, violin and guitar. The higher the recording quality
the better, but almost any recording will give you some idea of what your
EQ will do.

Using recorded sound as
your source, rather than a microphone on a voice or instrument, provides
exact repeatability for comparison of different control settings. It also
allows you to hear only what the mixer settings are doing, without the
confusion of hearing direct sound from the stage.

One factor that should make
the sea of knobs in front of you a little less imposing is the fact that
during a typical church service, relatively few controls need to be touched.
Many of the controls on your console are used to pre-adjust levels or determine
the destinations to which signals will be routed. It is not unusual for
an operator to use only the mute buttons and faders during a service. Trim
controls should be set in advance and need to be adjusted only if conditions
change dramatically. Likewise, channel assignments to sub sends or main
outputs are normally set and left alone. Once channel EQ adjustments have
been made for particular microphone, there should be no further need to
adjust EQ during the service.

Of course, there's a lot
more to mixing sound than we can get to in this article. That's what Sound
Advice is for. In the future we'll further explore what it takes to provide
the best sound possible in your worship service