936 Chapter 25
networking-think) the effect on the design of the
console architecture is actually surprisingly minor, and
the impacts such as they are will be dealt with piece-
meal as required. No, the control surface is the real
battleground.
25.16.1 Fader Automation
The first victims of automation were the faders. Once
heavy multitrack (16/24 track) had become common-
place, a severely limiting factor of human physi-
ology—only ten fingers—proved something of an
obstacle in a mixdown situation demanding consider-
ably in excess of that number. The hitherto classic solu-
tion—reduction mixes of subgroups of tracks to a more
manageable quantity—forces another tape generation;
this is not a good idea considering one of multitrack’s
touted advantages is freedom from bouncing.
To be able to remember, and subsequently modify if
need be, fader movements during a mix seemed like a
good idea. There were, and still are, two fundamental
approaches to this requirement:
- Remember the physical position of the fader and on
recall arrange for it to move physically to its
required position.
This first technique was introduced initially by
one major manufacturer (Neve’s NECAM system)
and with the availability of reasonably economical
motorized faders is now fairly widespread. Most
others fall broadly into the second camp. Moving
fader systems are dearly loved by their users
because of their unequivocable indication at all
times—by the actual fader positions—of what the
system is actually doing. It has one other major
benefit—the involuntary hysterical laughter it spon-
taneously generates from anyone who for the first
time sees a swath of motor-driven faders dancing
about on their own.
With the ready availability of such moving faders
at cost points suited to nearly every level of applica-
tion, moving fader automation systems have
become the de facto standard for both automated
analog and digital mixers. - Drive a voltage-controlled amplifier (VCA) from
the fader and on recall reapply the appropriate
control voltage to the VCA—the fader itself is not
then controlling the VCA, Fig. 25-105.
VCA systems remain viable in analog consoles,
though, since they offer advantages at that crucial
fader point that moving faders cannot alone fulfill.
Although VCA automation systems were once
implemented in a purely analog fashion, the fader
position values being stored by a PWM or
voltage-to-frequency conversion methodology on an
analog tape track, these techniques mercifully gave
way to digital manipulation and storage as soon as it
was practicable.
A nulling indicator, as described later, is usually
employed to match actual VCA gains to that notion-
ally indicated by the fader.25.16.2 VCAsSeveral functions in mixing consoles cry out for a
perfect and consistent controllable gain block. In addi-
tion to automated fader systems, dynamics control and
other analog-controlled gain stages could all benefit by
something that looks like Fig. 25-106. It is a black box
to which audio is applied, from which audio is extracted,
and a control port that determines how much audio is
passed. Ideally the law of the control signal should be
predictable and consistent. No biasing, no tweaks, no
singing, no dancing. Should be easy, right?As seen elsewhere, raw active electronic devices can
be used as gain-variable stages with varying degrees of
success, compromises, and weirdnesses; their limita-
tions are various but notably include limited audio
signal handling capability, high distortion, and often
nonlinear (or nonsensible) control-voltage laws. In feed-
back-style automatic gain-reduction circuits such as
compressors and limiters, the law of nonlinearity tends
to disappear within the servo-loop feedback and haveFigure 25-105. Simplistic VCA-type fader automation.Figure 25-106. Ideal gain controlStorage
mediumControl
fader+VEWrite
ReadAudio
outputAudio
inputVELiveVCAInputControl signal
linear dB/VPerfect
gain control
elementOutput