Studio Technologies 40 - Manual (Page 16)

Model 40 User Guide Issue 1, July 1994
Studio Technologies, Inc. Page 17
designation is simply a different way of
measuring signal level and is often used
when dealing with portable or consumer
audio equipment. The dBV designation
refers to dB referenced to 1.0V, rather
than dBu which refers to 0.7747V.
Talent Amplifier Mono Function
Many arguments where had while design-
ing the talent amplifier monaural function.
Was mono to be the sum of left and right
sent to both left and right channels? What
about level build up with phase coherent
signals that are in both the left and right
channels? After much head scratching it
was realized that the mono function that
most people are accustomed to is not
really a “true” mono function, but is the
sum of the left and right signals, dropped
in level by 3dB, and connected to the left
and right outputs. This is what is imple-
mented in the Model 35 and Model 38
Talent Amplifiers.
Input Level and the Talent Amplifiers.
Optimal performance of Model 35 and
Model 38 Talent Amplifiers depends on
the proper setting of the Model 40’s input
level controls. The headphone volume is
intended to be adjusted only by the level
controls on the talent amplifiers. If the
setting of the input level control vis-a-vis
the actual level of the source is not cor-
rect, the talent amplifier will simply not be
able to create the maximum volume in the
headphones or will exhibit excessive
distortion.
The Model 38 Talent Amplifier can also
exhibit reduced performance if the level
of the input source is significantly “hotter”
than nominal. The entire system has
plenty of headroom, but maintaining
proper signal levels, as usual, is important.
If the input level is excessive, a small
amount of bleed-through can be heard
with the Model 38’s cue mix level control
set fully counterclockwise. Instead of
having no sound in the phones, a bit of
sound can be heard. This is not a design
problem; the Model 38 has a sensitive
preamplifier section which doesn’t like
“seeing” excessive excursions in the left
channel modulation of the +23Vdc signal.
The Model 38’s power supply can reject
the left channel modulation within the
design parameters, creating a clean refer-
ence voltage for the stereo preamplifier.
Modulation levels outside the design
parameters show up in the reference
voltage!
Circuit Description
The information contained in this
section is not provided as an
endorsement for you to perform
repairs or modifications to StudioComm
components. Removing the cover or the
back panel from the Model 40 Central
Controller exposes personnel to hazard-
ous voltages. Repairs or modifications
should be performed only at the factory
or authorized service center.
Model 40 Central Controller
This information will help you under-
stand how the Model 40 functions and,
if required, help you identify where a
failure may be located. Please refer to the
attached block and schematic diagrams
while reading this material.