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C107. Further filtering is achieved by T filters in the console frame and AC coupling is via C86,
C87, C97 C98, C108 and C109.
The signal mutes are switched from switches SW6, SW7 and SW8 which toggle the bi-stable flip
flops formed by invertor IC28 via capacitors C123, C125 and C127. The mute all switch SW9
overrides the mute control lines when it is active and sends the mute all control line logic high to
activate other mutes within the console. Automation of the master mutes is achieved through
resistors R174, R179 and R184.
The solo switch logic is performed by NAND gates IC29 and IC30. These form bi-stable flip flops
which are triggered by switches SW11, SW12, SW13 and capacitors C133, C136 and C140. If a
solo switch is held down, a capacitor C134, C137 or C139 dis-charges and resets the flip flop; the
solo continues to be held on by diode D47, D48 or D49 until the switch is released. The master
solos perform in a different way to the other solos on the console. When solos on the console are
active they do not clear the master solos via the solo clear line; instead the solo on line temporar-
ily overrides the master solo by activating triple OR gate IC32. When the other solos on the
console are switched off the master solo is reactivated. If the solo in place switch SW10 is on and
the solo on line is active (indicating a solo on the console is on) the NAND gate IC31 sends
control messages to the CMOS switches IC7 and IC8 which replace the master output with
signals from the solo bus. IC31 also ensures the timely removal of any master signal on the solo
bus to prevent oscillation and sends a solo in place active signal to the input modules which
illuminates their mute LEDs. Because the master feed to matrix is before CMOS switches IC7
and IC8 it is possible to solo in place matrix outputs without oscillation occurring even if they
contain signal from the master module.
The record outputs are fed from the pre insert master left and right signals via potentiometers
RV4(104) and RV5(105) to amplifiers IC35 and IC41. Their output is sent to the mute CMOS
switch IC36 which is controlled by invertor IC42. The invertor forms two bi-stable flip flops
which are triggered by switches SW14 , SW15 and capacitors CI88 and C190. The output from
the mute circuits is fed to differential output amplifiers IC37, IC38, IC39 and IC40. Output
symmetry is adjusted by pre-sets VR16, VR17, VR19 and VR20 while high frequency stability
into any load is assured by filter capacitors C155, C156, C157, C158, C162, C163, C164, C165,
C174, C175, C176, C177, C181, C182, C183 and C184. Further filtering is achieved by T filters
in the console frame and AC coupling is via C159, C160, C166, C167, C178, C179, C185 and
C186.
The record outputs also feed to the peak reading meter rectifiers formed by amplifier IC35 and
IC41. These respond to which ever is the highest of the left and right signals and are calibrated by
pre-sets VR18 and VR21. The mono signal is fed via CMOS switch IC7 to a full wave peak
reading rectifier which is formed by amplifier IC43. 0dB adjustment is via pre-set VR22 and offset
adjustment is via pre-set VR23. The meter LED chains are driven from constant current sources
to meter IC45, IC46, IC47 and IC48.
9. Comms Module.
The comms module houses the intercom and talk system, solo monitoring and auto mute masters.
The comms and talk mic signals are amplified by VOGADs IC2 and IC4. These are designed to
operate with most types of un-powered low impedance microphones and will compress the sig-
nals to give a constant output of -19dBu. This level is then further amplified by amplifiers IC3 and
Summary of Contents for XL4
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