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THE STUDIO |
The diagram shows the arrangement of one of the larger studios, equipped with two or more microphones fed into a mixer in the listening room. The mixer had no level meter so was effectively used for balancing only. The output of the mixer was routed through the announcer's control unit. The announcer was able to select between the output of his own microphone and the mixer output. The output of this unit was then fed to the control room where its level could be adjusted at one of the control positions.
Outside each studio was a yellow light which was operated from the House Superintendent's office by the official responsible for the booking of studios. The control room engineers could switch on the studios' red or blue lights (there were separate control positions for transmission and rehearsal) and operate the cue lights. These functions were not available in the listening rooms, though in some cases the announcer was provided with the means of operating a cue light in the studio. This would enable him to cue, say, a conductor, where there was no visual communication.
There
were feeds back from CR for the various loudspeakers and headphones - there
was no monitoring directly from the mixer or announcers' control desk. Telephones
in listening and announcing rooms linked directly to CR. The studio and
announcing room had pushes to operate CR buzzers, and, in this instance,
a buzzer in a band room. Studios which might be used with the Dramatic Control
Rooms also had a means of operating a 'return light' in the DCR as a means
of cueing the producer.right - A six-channel listening room mixer.
left - A three-channel listening room mixer.In addition to the potentiometers, the desk contained the necessary microphone decoupling arrangements and circuitry to reduce the 300 volt high tension supply to values suitable for operating the condenser microphones. These mics had their preamplifiers built into the microphone casing.
right - An announcer's control desk. What appears to
be a fader knob actually operates the switch which selects either the announcer's mic or
the output of the listening room mixer. Announcements could thus be made without the studio
hearing them or having to be silent - hence the alternative name ('Silence Room') for these
announcers' rooms. Again, the desk contained the necessary circuitry for the microphone.
Wiring in the studios ran in iron troughs behind removable wainscoting. Troughs in the concrete floors allowed the cables to run between the various rooms in the studio complex. The cabling back to the control room ran in cable ducts built into the office sides of the studio tower walls. These ducts ran from sub-basement up to the eighth floor. The cables then ran in horizontal ducts into the false floor of the control room.
CONTROL ROOM MIXERS
On the previous page we have looked at the switching facilities associated
with the CR control positions, here we look at the mixers. Some positions
were equipped with mixers handling four sources, others could cope with
only two.The two-channel mixers had a single fader which cross-faded between the two sources. With the fader fully anti-clockwise the first source was faded up and the second down. Moving the fader clockwise increased the level of the second source until, with the fader central, the two sources were at equal strength. Further advancing the fader clockwise reduced the level of the first source. The output of the fader was routed through the main control potentiometer.
On the four channel mixers the two outer faders each cross-faded
between two sources. The central fader took the outputs of the outer ones and handled them
similarly. Finally the output of that fader was fed to the main control, lower left.The main control potentiometer had 26 studs, with a level change of 2dB per stud over most of its range. The final stud before the circuit was broken gave an attenuation of 60dB. The 'cross-faders' used similar pots. As only half of the total travel of the control had to adjust the level of a source from off to maximum, these faders produced a much coarser fade and the final stud before the off position gave an attenuation of 40dB. It was therefore the main fader that was used for level control.
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