Handbook for Sound Engineers

932 Chapter 25

25.15.13 Mixes to Outputs

The virtual-earth mixing buses of the console all end up
in identical mix-amp, attenuator, and line amp configu-
rations. The exceptions are the mono sources (effect
sends) that have individual master level controls rather
than ganged stereo attenuators and the PFL (which does
not need a level control because it is a purely moni-
toring function). These back-end stages are homed in
two of the very few on-off system blocks in this design:
stereo monitor/mix (with the master fader) and the PFL
summing occupy the master module, while the
remaining auxiliary functions are summed in the auxil-
iary master module, Figs. 25-86 and 25-87.

The outputs are taken to the jackfield, where they are
normalized to their appropriate destinations and directly
bridged by the differential inputs of the monitor selector

switching matrix (adjacent to the field). It is assumed

that output transformers or electronic balanced output

line amps will be implemented.

25.15.14 Master Functions

Fig. 25-102 shows a simple console master function

circuitry. All the clever switching is done in the chan-

nels, allowing this unit to be little more than switch

contacts. No debouncing is necessary since the master

buses directly actuate the set and reset latch functions of

the channel function registers.

Lockouts are arranged on the fader main/reverse

selection and master monitor A and B switching to

prevent both of the relevant control buses from being

switched at the same time; this could otherwise lead to

Figure 25-102. Desk master function control circuitry.

Master fader

reverse bus

Master mode buses

Mode master select

Switching (momentary)

Master reset

bus (M.R.B.)

Switch-on reset

timing circuit

Master A A check

check bus

Master B

check bus

Faders

reverse

(both switches momentary)

All diodes

1N4148

Rec Dub Mix Dir

B check

Solo safe (latching)

Solo safe bus

Master fader

normal bus