TL Audio VTC - Manual (Page 42)

42
The monitor input is connected to the balanced input stage, IC5A, and then to the pre-set gain stage,
IC4B. The pre-set, RV11, is used to calibrate the module input by matching the monitor gain to the
line input 0dB gain. It is only necessary to recalibrate RV11 if the input gain controls RV1 or RV2
have been replaced, and should be performed by feeding a 0dBu signal into the line input, setting the
line and monitor gain pots to their centre detent, and noting the level at the insertion send. The signal
should then be moved to the monitor input, the Flip switch activated, and RV11 adjusted to obtain
the same insertion send level.
The module presets are only adjusted at the module test stage, and are independent of the frame
position in the console. Calibration of line and monitor path gain is achieved by adjusting the presets
on the valve PCB (refer to the calibration procedure) and must be reset after changing input modules.
The monitor input may be changed to -10dBu sensitivity by fitting the jumper link J2 on the module.
After the gain stages and Flip switch, the monitor signal is routed off the module to the valve stage.
The channel insertion return and monitor paths are returned from the valve stages to the module by
signals INS RTN (CN1-15C) and MON VOUT (CN1-14C) respectively.
PC331 also contains the Aux sends (see CD1331 sheet 3), and the Direct Output (sheet 4). The Direct
Output has trim controls for level, RV9, and balance, RV10. Fitting J1 reduces the nominal output
level to -10dBu.
3.7. Equaliser (CD1332).
The equaliser is divided into a high and low shelving pair, IC5, and two fully parametric bands,
IC1,IC2,IC3 and IC4.
The HF / LF and HM / LM bands may be separately switched into the monitor path on PC333, hence
PC332 contains two equaliser signal paths, plus a third path through the channel EQ on/off switch,
SW1.
3.8. Faders and Routing (CD1333).
PC333 contains the fader circuitry, routing and mute controls. The mute controls are of the
electronically operated “fast fade” type, with additional interaction with the solo-in-place system and
optional automation system.
The mute switches themselves are non-latching, and require toggling on and off by the flip-flops
IC10A and IC10B. These flip-flops are cleared at power on by the reset circuitry, and then clocked
by the mute switches via the debounce circuitry at IC11A and IC11D. The audio muting is effected
by signals CHAN MUTE and MIXB MUTE, at the outputs of IC11E and IC11B, controlling IC12B
and IC12A respectively. The mute circuitry may also be activated by the SOLO signal (CN5-32A),
provided that Solo-in-place is selected on the Master Module (causing SOLO EN~ at CN5-32C to be
logic low) and the path itself is not also soloed (SW7 and SW1).
The Mute LEDs are also controlled by CHAN MUTE and MIXB MUTE, but may additionally be
illuminated at half intensity when an Automation System mute is applied (via Q6 and Q7). This is an
optional feature, only supported by certain automation systems.
When fitted to the console, the Automation System VCA paths are selected by SW9 and SW3.
Operation of the Auto switch on consoles where no automation system is fitted appears to have no
affect, as bypass headers on the backplane, PC337, maintain the signal paths. Moving Fader