REVISION C
BMX SERIES III CONSOLE
71
PACIFIC RESEARCH & ENGINEERING
The Patch Input signal is buffered by balanced differential amplifier U1A operating at unity gain, and
then routed to the INPUT MODE switch. The output of the mode switch is connected to the mix fader,
and CUE bus relay K2.
The mix fader “in-hand” attenuation of 15 dB is recovered by fader buffer amplifier U2A to the -10 dBu
internal system level, and routed to the PAN pot and the pan insert switch. The pan switch selects
between the attenuated output of the fader buffer and the output of the pan pot, and then routes the signal
to amplifier U3A, which operates at a gain of 3 dB. The output of U3A is connected to channel on/off
relay K3 and SOLO relay K4. The channel on/off relay then routes the signal to the output bus
assignment switches and the direct output lines.
With Sends
PRE/post fader Send switch S3 gets its PRE-fader input from INPUT MODE switch, and its post-fader
input from amplifiers U3A and U3B. The outputs of the two-section Send fader are routed through Send
relay K1 to the two Send ON/off switches. The two Send signals are a monaural mix of the left and
right channels. However, this module may be modified for stereo Send operation by following the
procedure outlined in Section 5.3.
LOGIC
The module is provided with two sets of control logic, one for each of the A and B inputs. This logic
includes the capacity to provide independent machine and remote controls for the ON, OFF, CUE, and
SOLO functions for each input. A contact on the A/B input selector switch is routed to integrated circuit
switches U206, U200, U212 and U201. U206 selects the A/B logic status of the module, as determined
by programming switches S200, U200 (the A and B remote control input lines), and U212, U201 (the
A and B output tally lamp and control pulse lines).
When the module or the selected input’s remote control ON button is pressed, the output of U202A will
go high. This output is routed to channel on/off flip-flop U209, and CUE and SOLO reset enable
switches S205-1 and S205-2, respectively. The low “on” output from U209 pin 3 is routed to the
monitor mute gates in U207, to delay circuit R239, C213, R240 and U208D, to channel ON/OFF relay
drive transistor Q204, and also to ON relay K3. This low is also connected to output switch U212, and
to “on” lamp drive transistor Q205. The high “on” output from U209 pin 11 is routed to “off” lamp gate
U205A, through “start” pulse generator circuit U211A to output switch U212, and through timer “reset”
pulse generator U211B to transistor Q207.
When the module or the selected input’s remote control OFF button is pressed, the output of U203 will
go high. This output is connected to channel on/off flip-flop U209, and resets it to the “off” state. The
output of U209 pin 3 goes high, and bypasses the turn-on delay network via diode CR202 to turn off
the channel relays. The channel audio is also switched off when either the A or B input selector switch
is operated by generating a short pulse into “off” gate U203 pins 11 and 12, respectively.
Output driver short-circuit protection is provided to prevent damage caused by shorts in the output lines.
As an example of this protection, consider the case when the A INPUT ON TALLY lamp is powered;