GEAR 23_COVER - JHS

KEVIN ASTON’S
TECH TALK
What’s a mixer?
Do you know your PAN from your PFL? We’ve all felt intimidated
by the layout of mixing desks, but fear not - Gear’s tame boffin
Kevin Aston guides you down a desk channel strip using the
ALLEN & HEATH ZED22FX desk.
It only takes an onstage cry of ‘Can I have
less reverb in my monitor?’ from the vocalist
to elicit one of two reactions from anyone
standing in the proximity of the mixing desk;
a) someone who goes straight to the
respective controls and takes out some of the
reverb as requested or, more likely, b) total
paralysis caused by control confusion.
Don’t be afraid to admit it, mixers can be
daunting to look at, with seemingly hundreds
of multi-coloured controls with function
names which only serve to baffle even more.
So, without further ado, let me lead you
gently into the land of the mixing console...
A mixer can be referred to by a number of
titles; mixing console, board and desk are
often used but each means the same thing.
A mixer is a device that allows you to balance,
position, effect and equalise a number of
sound sources (inputs) into a good sounding
sonic image referred to as ‘..a mix’. In the
mix, you can add effects to some channels
but not others, and position instruments to
a location in the stereo sound field. You can
route channels to outboard equipment that
produces an interesting effect and ‘sculpt’
the sound of each channel with a dedicated
equaliser where the bass, mid and treble can
be varied in such a way that the whole song
‘gels’. And you can dramatically improve your
music made of multiple tracks by learning
how to mix.
ALLEN & HEATH ZED22FX
A mixer is actually a very simple animal.
I know it looks like it has acres of controls,
but all it does is to allow you to combine and
route audio signals from a set of inputs to a
set of outputs. More advanced models will
allow you to add varied signal processing
effects.
The main image on this page shows an Allen
& Heath ZED22FX mixer. I chose this for my
example as it is equally at home as a live
mixer, or for recording. The ‘22’ tells you it
has 22 input channels, which it can mix
(combine) into 2 channels – I’ll return to
this later.
Spend a few minutes looking at any
mixing desk, and you will notice
that every mixer layout follows a
simple and logical sequence of
control layout. Starting from the
left hand side, the panel is set out
in distinct vertical ‘strips’, each
strip being the same. These are the
individual input channels, the ‘22’
in the mixer’s model number.
These are the
22 input
channels.
TOO
LOUD
Moving
to the
right hand
side, the
layout has changed
slightly, but it still
follows the same logical
layout principle. The two red
sliders refer to the two outputs.
So far so good, but what exactly
does a mixer do?
You take a number of input signals;
vocal microphone(s), keyboards,
guitars and drums. Listening to the
band playing, the guitarist may be
too loud compared to the rest of
the band (never, it’ll be the drummer
or the bass player – guitarist Ed).
Your mixer gives you full control
over this. Each sound source goes
through one or more channels.
Using the input levels and EQ, you
can “shape“ each sound and, using
the channel faders, you control each
channel’s volume level. Using these
few controls, you can “place”
sounds across the stage using the
Pan controls. You can bring a sound
to the front of the stage by gently
boosting the volume and EQ on that
channel. OR, you can move the
sound to the back of the stage by
backing off the bass EQ and lowering the
volume of that channel.
OK, let’s jump in and take a look at a channel
strip of an Allen & Heath ZED22FX, and
explain what the controls do. The first 16
channels are all exactly the same, and are
termed MONO INPUTS.
Mic In
Use this XLR input to connect your microphones
or DI boxes. It is a balanced input, wired in
the normal convention of Pin 1 = chassis, Pin
2 = hot signal (+), and Pin 3 + cold(-) signal.
The Mic input connects to the heart of any
mixing desk, the preamplifier. The preamp is
used to boost the weak -70 dBu to -50 dBu
nominal output levels of microphones to
around +4 dBu.
Line In
Use this connector for plugging in ‘Line Level’
instruments such as keyboards, samplers or
drum machines. It can also be used to accept
the returns from multitrack tape machines
and other recording media. It is a balanced
input, wired in the normal convention of
(stereo socket) Tip = hot signal (+), Ring =
cold signal (-) and Sleeve = chassis. If you
connect a plug to the Line Input, it
overrides the XLR input
socket.
Insert
Point
This is used to
connect external
signal processors
such as compressors or limiters within the
input module. The Insert Point allows external
devices to be placed within the Input Path.
This is a stereo socket, wired to Tip = signal
send, Ring = signal return and Sleeve = ground.
Gain Control (Input Sensitivity)
Sets how much of the signal from the mic or
line inputs is fed to the channel. This gain
runs from -6dB to +63dB with the XLR input,
-10dB to +26dB when using line in.
HPF (High Pass Filter)
As the name suggests, this switch cuts out
the very lowest frequencies of a sound whilst
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