Studio Technologies 742A - Manual (Page 11)

Model 742A User Guide Issue 1, July 2012
Studio Technologies, Inc. Page 11
Audio Mixer
System Components
The shipping carton contains a Model
742A Audio Mixer, user guide, and AC
mains cord suitable for use in North Amer-
ica and Japan. When installed in other
locations your dealer or distributor should
provide a suitable AC mains cord.
Locating the Unit
Now that the Model 742A’s configura-
tion has been reviewed and, if required,
revised, the unit can be mounted in an
equipment rack. Physical access and
viewing angles are the primary issues to
be considered when choosing a mount-
ing location. By its very nature as an audio
mixer, an operator will need easy access
to all the controls. A good sight line to the
LED level meters, located on the right side
of the front panel, is also important.
As a device that contains high-gain audio
stages, hum and noise pickup is possible
by way of the chassis and associated
cabling. Locating the unit away from
devices that radiate strong AC fields is
an excellent idea.
During normal operation, access to the
Model 742A’s back panel is not typically
required. However, as the +48 volt phan-
tom power DIP switches are located on
the back panel it’s possible that access
would be helpful. In most cases the phan-
tom power switches can be set and kept
in their desired on or off positions. By the
very nature of phantom power, the pres-
ence of it on a microphone input shouldn’t
impact the performance of microphones
that don’t utilize phantom power. But there
may be cases where their settings need to
be changed.
Also accessible on the back panel is one
trim potentiometer that may need to be
adjusted prior to the Model 742A going
into service. This trim pot sets the level of
the reference tone direct output. Please
refer to the Post-Installation Calibration
section of this guide for details.
Mounting
Once a mounting location has been se-
lected installation can begin. The Model
742A requires one space (1.75 vertical
inches or “1U”) in a standard 19-inch
(48.3 cm) equipment rack. Secure the
unit into the equipment rack using four
mounting screws, two per side.
Mic/Line Inputs
The Model 742A contains four input chan-
nels that are compatible with microphone
and line-level sources. (Refer to Figure
3 for a detailed view.) Each input uses a
3-pin female XLR connector. Prepare the
mating connectors (males) so that pin 2
is signal high (+ or hot), pin 3 is low
(– or cold), and pin 1 is shield.
It’s possible that some of the mic/line
inputs will be wired to an input/output
(I/O) panel located on the side or rear of
a broadcast vehicle. If this is the case, it’s
also nice to have one or two of the inputs
“multed” to connectors inside the vehicle.
This will allow the rapid connection of
microphone or line-level signals during
specialized situations. For example, during
inclement weather on-air talent may wish
to connect a microphone to the Model
742A from inside a vehicle.
To minimize potential hum or noise prob-
lems, it is recommended that microphone-
level signals connected to the mic/line