Service manual
11
GROUP MODULE
This is a double module for use as either two independent output groups or one stereo output
group. It is constructed on two interlinked pcbs. Only one of the groups is described except
where operations affect both groups simultaneously.
Direct Input [Diagram XL310_A1.DGM].
The signal appears at connector 'A' (ST1) pin 19 [hot] and pin 20 [cold] from the XLR socket
on the console back panel. First order R.F. filtering is provided by R14/C16 and R19/C17,
and over-voltage protection by D2/D3 and D4/D5. IC2 operates as a differential amplifier whose
common mode rejection is set by VR1 at the factory for maximum rejection [typically 85dB]
at 100Hz. The signal then passes through C21 to the direct input PFL/solo switch S1 and via
C20 and the level potentiometer RV1 to the inverting buffer IC3b. A feed is taken from this point
to the solo routing system ( detailed later) as well as via the direct in mute circuit Q3 and Q4
to IC1b where it is summed with the mix buss signal. The direct in mute circuit is controlled by
S2 which is used to switch the fets gates between 0V and Vref. The voltage ramps up or down
at a rate controlled by R32/C44 and R31/C24 to provide a clickless transition.
Group Mix input [Diagram XL310_A1.DGM].
The group mix buss signal arrives via connector 'B' (ST2) pin 24 at the virtual earth summing
stage IC1a, and is reinverted and summed with the direct input signal by IC1b. It is fed via the
insert stage to non inverting buffer IC6a and then to the vca stage as well as the pfl switch S4
[Diagram XL310 - A2.DGM]. The insert or by-pass is selected by S3. The insert consists of IC4
as the balancing network for the insert send which appears at connector 'A' pins 8 [hot] and
9 [cold], it is protected from excess voltage by the diode bridge D7-10, and set for maximum
common mode rejection at 100Hz by VR2 [typically 85dB]. The insert return appears at
connector 'A' pins 6 [hot] and 7 [cold]. It is protected from R.F. contamination by R36/C35 and
R41/C36 and from over-voltage by diode bridge D11-14. IC5 is a differential amplifier whose
common mode rejection is factory set by VR3 to maximum at 100Hz, typically 85d.
VCA and Outputs [Diagram XL310_A2.DGM].
The vca is based around IC6b, IC7 and IC8a in the audio path and IC8b in the control path. The
control voltage from the internal module level control RVX and the fader tray level control via
connector 'B' pin 9 is summed with an offset voltage by IC8b. This offset voltage adjusted by
VR7 is used to define the available vca control range. It has been preset in the factory and should
not require adjusting unless the vca has been replaced. The output voltage of IC8b, and therefore
the control range of the vca, is further clamped by D55 and D56 to prevent overshoot.
The vca output is routed to ST6 and ST7 for master and matrix, post fade pre mute output
options as well as the main group mute circuit consisting of analogue switch IC9a and IC9b. It
also appears at the modules internal meter connector (ST5 pin 1) as well as on connector 'A' pin
18s for connection to the optional meter bridge. An alternative link point for pre-mute solo send
is also fitted. Note: if this is used, it is out of phase with any direct input.