Making the Most of Your Mixer
EMX512SC/EMX312SC/EMX212S
15
BASIC
Signal Levels and
the Decibel
Let’s take a look at one of the
most commonly used units in
audio: the decibel (dB). If the
smallest sound that can be heard
by the human ear is given an
arbitrary value of 1, then the
loudest sound that can be heard
is approximately 1,000,000 (one
million) times louder. That’s too
many digits to deal with for
practical calculations, and so the
more appropriate “decibel” (dB)
unit was created for sound-related
measurements. In this system the
difference between the softest
and loudest sounds that can be
heard is 120 dB. This is a non-
linear scale, and a difference of 3
dB actually results in a doubling
or halving of the loudness.
You might encounter a number of
different varieties of the dB: dBu,
dBV, dBM and others, but the
dBu is the basic decibel unit. In
the case of dBu, “0 dBu” is
specified as a signal level of
0.775 volts. For example, if a
microphone’s output level is –40
dBu (0.00775 V), then to raise
that level to 0 dBu (0.775 V) in the
mixer’s preamp stage requires
that the signal be amplified by
100 times.
A mixer may be required to
handle signals at a wide range of
levels, and it is necessary match
input and output levels as closely
as possible. In most cases the
“nominal” level for a mixer’s input
and outputs is marked on the
panel or listed in the owner’s
manual.
Making Better Mixes
Approaching the
Mix—Where Do You
Start?
Mixing is easy, right? Just move
the faders around until it sounds
right? Well, you can do it that
way, but a more systematic
approach that is suited to the
material you’re mixing will
produce much better results, and
faster. There are no rules, and
you’ll probably end up developing
a system that works best for you.
But the key is to
develop a
system
rather than working
haphazardly. Here are a few
ideas to get you started:
Faders Down
It might sound overly simple, but it
is usually a good idea to start with
all channel faders off—all the way
down. It’s also possible to start
with all faders at their nominal
settings, but it’s too easy to lose
perspective with this approach.
Start with all faders down, then
bring them up one by one to fill
out the mix. But which channel
should you start with?
Example1:
Vocal Ballad Backed by
Piano Trio
What are you
mixing? Is it a song
in which the vocals
are the most
important element?
Unbalanced noise
Noise
Source
Cable
Receiving device
+ 20 dBu
0 dBu
0.775 V
-20 dBu
-40 dBu
-60 dBu
The inputs and outputs on home-use audio gear
usually have a nominal level of
–10 dBu
.
Most professional mixers, power amplifiers, and other
types of equipment have inputs and outputs with a
nominal level of
+4 dBu
.
Microphone signal levels vary over a wide range
depending on the type of microphone and the source.
Average speech is about
–30 dBu
, but the twittering of
a bird might be lower than
–50 dBu
while a solid bass
drum beat might produce a level as high as
0 dBu
.
