molecules a series of pressure waves are created.
As long as the frequency of these vibrations is with-
in the range of human hearing (roughly 20 to
20,000 cycles per second, depending on your age),
we hear them as sound waves, and when they
reach our ear drum we hear the cymbal. But if we
want to do anything more with this sound record
it, for example we need to turn it into something
that we can manipulate more easily than pressure
waves in air.
In analogue audio circuits, sound waves are rep-
resented by continuous electrical signals. At one
end of a typical audio chain, a microphone uses
the vibrations of air against its diaphragm to gener-
ate a varying electrical current, and at the other a
speaker uses a varying electrical current to produce
vibrations in the air next to its cone.
Analogue electronics are always prone to noise
at the very least because the the random thermal
motion of electrons in components will produce
some noise though this can be minimised
through good circuit design, the use of high quality
components, and good construction.
In digital equipment, the audio waveform is rep-
resented by a series of numbers. An analogue sig-
nal can be turned into digital form with an ana-
logue-to-digital converter, which measures an ana-
logue input voltage at regular intervals and gener-
ates a sample (a number that represents the
instantaneous strength of the signal) each time. A
converter that runs at a sampling rate of 44.1kHz
samples the signal 44,100 times per second, and in
a well-designed converter the size of the samples
should be in direct proportion to the input voltage.
A 16-bit converter can resolve 65,536 levels.
A 20-bit converter can resolve 1,048,576 levels.
A 24-bit converter can resolve 16,777,216 levels.
Because numbers can be described and copied
with absolute precision, digital audio signals can be
passed from one machine to another, or from one
part of a digital mixer to another, with no change to
the sound. An analogue signal, on the other hand,
cannot be passed through any component without
SECTION
1: The Basics Of Digital Mixing
3
THE BASICS OF
DIGITAL MIXING
Welcome to the Spirit Digital Mixing Handbook
the essential guide to the world of digital mixing.
Over the years it has become increasingly easy for
the solo musician, producer or small band to
assemble a small studio, and with the advent of
affordable digital technology, many of us now have
access to our own sophisticated recording facilities
capable of producing release-quality material. As
the central, and perhaps the most complex, single
piece of equipment in the studio, the mixer has
always been the most important item to get to
grips with. Hence this guide, which helps you
understand the principles and practice of digital
mixing. Enjoy!
A. Analogue & Digital
Whats The Difference?
The move from analogue to digital technology in
the world of audio is a revolutionary one, not just
a small step. The technology is fundamentally dif-
ferent, hence many of the the advantages of digital
over analogue. Although most practical aspects of
recording and mixing are unchanged, some are
not, and it helps greatly to understand some of
the principles of digital audio.
Whereas analogue electronics deal with contin-
uously variable quantities (such as voltages and
currents), digital electronics deal with discrete val-
ues - numbers that can take only one of a prede-
fined set of possibilities. Digital circuits do this by
dealing with 1s and 0s, represented by the differ-
ence between a switch being on or off, or a voltage
being present or not.
This difference means that digital and analogue
systems represent sound in very different ways.
What we perceive as sound is in fact a vibration in
the air. Hit a cymbal and it vibrates, transmitting
the movement to the air around it, and as the
vibrations are passed on to more and more air
Guide.qxd 02/03/1999 11:25 Page 3
