(1) If the trouble is in the preamplifier, then of course it would be a matter of checking tubes
and other items or perhaps circuit tracing the preamplifier.
(2) However, a weak signal would usually be caused by a weak tube in the circuit. Other
possibilities, although less probable, are low B+, low filaments, components value change, and other
minor items.
f. The mixer control is one part of the control console which is used extensively and causes
some trouble during operation.
(1) The mixer or variable attenuator is nothing more than a gain control; therefore, it has a
sliding arm contact.
(2) The sliding contact may become dirty and cause noisy operation of the control. This is
very apparent in the gain rather than a smooth change. The trouble can be eliminated by cleaning the
wiper arm contacts with a good contact cleaner, or some other cleaner as recommended by the
manufacturer.
Learning Event 3:
DESCRIBE AND IDENTIFY THE EQUIPMENT USED IN A COMPLEX AUDIO CONSOLE
1.
Complex audio console. The basic configuration of the equipment consists of a main audio
console, an auxiliary mixer console, and an auxiliary control console.
a. At the main audio console, mixers are provided for four microphones, one turntable, one tape
station, one network audio circuit, and one remote audio circuit, providing a total of eight. By means of
lever keys, each program source may be switched to a program bus or on audition bus. Keys for the
microphone positions also provide studio speaker control, so that the speaker is locked out during a
broadcast. Talkback facilities allow communication to the studio, except during on-the-air periods.
(1) Twelve microphone circuits may be connected permanently to the console, and through
the use of lever-type switches, four of the microphones can be assigned to preamplifiers and mixers.
Each mixer output is controlled by a key-type switch, so that the output may be connected to either the
program or the audition bus.
(2) Either of two methods may be used to connect the auxiliary mixer and the main audio
console. By paralleling the audition and program buses of each, a total of eight microphone mixers are
available. In addition, a speaker interlock circuit is provided on the audition-program switches.
(3) By connecting the program output of the auxiliary mixer, one master mixer and four
subcontrol mixers are provided. Such a configuration is desirable when an orchestral program is to be
broadcast. Proper instrument balance can be obtained by settings of the individual mixers, and the
master mixer can be used to provide cutoff or fading of the entire group.
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