Studio Technologies M233-01151 - Manual (Page 18)

Issue 5, November 2014 Model 233 User Guide
Page 18 Studio Technologies, Inc.
Microphone Preamplifier Gain
Switches SW1-1 through SW1-5 are used
to select the gain of the microphone
preamplifier. The choices are 20, 30, 40,
50, and 60 dB. Only one switch should
be enabled at a time. There’s no problem
changing the gain setting while the unit
is operating. Audio clicks or pops might
occur during gain transitions, but this
shouldn’t be a major issue as long as
associated monitor loudspeakers are
temporarily attenuated or muted.
Selecting the correct amount of gain for an
application might take a little experimenta-
tion. The goal is to bring the microphone’s
signal up to line level, nominally –2 dBu,
on the Model 233’s main output. Operat-
ing at this signal level will help to ensure
the delivery of “clean” audio to the con-
nected device. The output of the Model
233’s microphone preamplifier is used
by both the main output and, by way of
the compressor circuit, the talkback func-
tions. So creating a nice “hot” signal will
help maintain audio quality, specifically
the signal-to-noise ratio, when driving the
often-lengthy cable runs.
Figure 4. Microphone preamplifier gain switch
settings
To prevent unauthorized personnel from
changing the configuration settings, a
security plate is attached to the bottom
of the Model 233’s enclosure. For conve-
nience, text and graphics on the security
plate provides a summary of the configu-
rable parameters and related information.
Refer to Appendix A for a representative
view. The security plate is held in place by
means of four rubber bumpers (“feet”) that
have built-in screws. Using your fingers,
remove the four bumpers so that the plate
can be removed. Refer to Figure 3 for a
detailed view of the configuration switch
assemblies.
Figure 3. Bottom view of Model 233 showing
configuration switches, trim pots, and
compressor active LED
Microphone Preamplifier Gain
and Phantom Power
Five switches are used to set the gain of
the microphone preamplifier. One switch
is used to select the on/off status of the
phantom power supply.