Yamaha PM4000 Operating Manual page 111

trolled Amplifier) in the input module. The audio signal
flowing through that VCA is, in turn, increased or
decreased in level according to the control voltage
applied to the VCA. One advantage of the VCA is that
the control voltage applied to it can come from more
than one point. In fact, when one or more of the input
channel's VCA ASSIGN switches [22] is engaged,
control voltage from the correspondingly numbered
VCA Master Faders [47] is also applied to the channel
VCA The circuitry is such that the VCA Master will
cause the assigned input channel(s) post-fader output
levels to ride up and down, scaled to the channel Fader
setting. Of course, the channel(s) output signal must
still be assigned somewhere.
NOTE: It may not be obvious, but VCA master faders
and VCA assign switches have nothing at all to do with
where the audio signal goes. They only affect its level.
The signal must be assigned via bus assign switches,
and/or Aux Send controls.
If the signal on several channels is assigned directly
to the stereo bus using the channels' ST assign switch
[3], then the VCA Master to which those channels are
assigned will act like a Group-to-Stereo fader. If the
channels' output is assigned to a Group bus using a
Group assign switches [1], then the VCA Master [47] to
which those channels are assigned will control the level
applied to the Group Master [42], which is somewhat
redundant but does serve some useful purposes.
What cannot be done with a Group Master Fader
[42] that can be done with a VCA Master [47] is control-
ling the post-fader AUX SEND levels from groups of
input channels. While it's true that the Aux Send
Master LEVEL controls [38] affect the overall bus
output level on the eight aux busses, each of these
busses can be considered a discrete output. Of the many
input channel AUX SEND controls that may be feeding
a given Aux Send Master LEVEL control, some can be
controlled by one VCA Master, and others by another
VCA Master. Thus, when "subgrouping" is accom-
plished with the VCA Master Faders, the output of
affected input channels is controlled more completely.
That is, the channels' Group, Stereo, and Post-Fader
Aux Send outputs are all affected by the assigned VCA
Master(s).
What cannot be done with a VCA Master Fader [47]
that can be done with a Group Master Fader [42] is the
processing of a single, mixed signal. Consider, for
example, that a given group of signals must be com-
pressed... say the backup vocal mics. If the several
input channels which accommodate backup vocals are
all assigned to a single Group Master Fader, then one
compressor/limiter can be inserted in the Group IN-
SERT IN/OUT patch point [118], affecting the mixed
signal on that group mixing bus. On the other hand, if
those same input channels were instead controlled as a
"group" by a VCA Master Fader, and the channel
outputs were assigned to various group mixing busses,
then it would be impossible to compress the backup
vocal mix. Instead, multiple compressor/limiters would
have to be inserted in the individual channel INSERT
IN/OUT patch points [102]. The latter approach is more
costly, and also applies the effect to all the channel's
outputs, rather than just to a specific group.
VCA Master Fader grouping is often useful for
control of scenes, songs or sets, whereas conventional
Group Master Faders are often useful for control of
related groups of mics and instruments. For example,
one VCA Master might be assigned to control all drum
microphones. Another VCA Master might also be
assigned to the same drum microphones, plus any
percussion and guitar mics. One VCA Master would
then affect drum levels, while the other would affect the
entire rhythm section.
In some cases, multiple channels that are assigned
direct to the stereo bus can be controlled in groups by
the VCA Masters, while other channels can be assigned
to different Group Master Faders, and the Group
Masters, in turn, can be assigned to stereo; using this
approach, one has the equivalent of 16 groups mixed to
stereo.
There is one further distinction between VCA groups
and conventional groups. If one were to use conven-
tional groups to control scenes, sets or songs, a given
input channel might well be assigned to several group
mixing busses. The mix matrix would then be used to
combine those busses, with the group master faders
serving as scene controllers. If, in this instance, two
Group Master Faders were raised to nominal position,
and the same input channel was assigned to both of
those groups, that channel's level would rise 3 dB in the
combined matrix output, throwing it out of balance with
other single-assigned channels. This is because that
channel signal is being added together twice in the
matrix.
If instead of using conventional Group Master
Faders, VCA Master Faders were used to control the
scenes, and one input was assigned to two (or more)
VCA Masters, the above level "build up" would not
occur, and the correct balance would be retained. That's
because when VCA Master Faders are set to nominal
position, they output zero volts... which means they
don't change the level coming from the input channel.
Whether one, two or all eight VCA Master Faders are
assigned to a given input channel, the channel's output
level will not change so long as the VCA Masters are at
nominal.
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