Hints On Circuitry For Remote Control Of - Yamaha PM4000 Operating Manual

6.15 Hints on Circuitry For Remote
Control of the VCA Masters
and Mute Groups
The VCA/MUTE CONTROL connector on the
PM4000 rear panel is provided primarily so that two
consoles may be linked, and just one console's VCA
MASTER FADERS and/or MUTE MASTER switches
will affect both consoles input channels. However, it is
possible to create an independent controller so that
these functions can be remoted from the console. One
possible application would be to remotely adjust mix
levels in the middle of a venue even though the console
is located in a booth. Another possible application would
be the creation of a limited automation system. Yamaha
does not offer detailed instructions for this type of
remote control. However, we do present here a sche-
matic diagram of the VCA control fader circuit which, if
constructed externally by a competent technician and
interfaced via the VCA/MUTE CONTROL connector,
can do the job.
Note that the nominal fader position delivers 0 VDC
to the VCA, and the VCA operates at unity gain with
that input. The control voltage scaling is approximately
-20 dB per volt DC in the linear range of fader travel
(above -50 dB on the fader scale). Thus, at maximum
upward fader travel, a single fader will deliver about
0.5 volt negative, which drives the VCA to +10 dB of
gain. If several VCA faders are set above nominal and
assigned to a channel, the maximum negative voltage
that will be applied to the VCA is -1.2 VDC (a DC
Figure 6-17. Suggested Circuit for Remote Control of a VCA Master Group
limiter circuit prevents any more negative voltage from
being passed and turns on the VCA MAX LED). This
corresponds to +24 dB of gain. At minimum VCA fader
setting, the output is +10 VDC, corresponding to over
100 dB of attenuation.
The VCA and MUTE connections are illustrated in
Figure 2-13. In order to mute a group, ground the
conductor corresponding to that group. The console's
VCA MASTER/SLAVE and/or MUTE MASTER/SLAVE
switch(es) must be set to the SLAVE position in order
for the corresponding remote control to take effect on
the designated busses and mute groups.
WARNING: Only qualified service techni-
cians should attempt to construct and
connect any circuit to interface with the
PM4000 VCA/MUTE CONTROL connector.
A circuit or wiring error could severely
damage the console, and such damage is
not covered under the terms of the
PM4000 Warranty. Improper grounding
could also create noise and/or safety haz-
ards. This information is provided only to
illustrate the extent of such a modifica-
tion; the PM4000 Service Manual should
be consulted before actually building any
remote control device.
Refer to the parts list and the VCA control voltage
curve on the following page.
Page 6-18