Data Sheet

Studio Technologies, Inc. StudioComm 74/75, Issue 1, Page 2
The Model 74 provides two 6-channel monitor outputs. A powerful system feature is the ability to configure the monitor outputs
to meet the exact needs of an installation. In a “straight-ahead” application the monitor outputs might be configured to sup-
port two independent surround (5.1) loudspeaker systems. Alternately, one surround and one stereo monitor system could be
connected. However, other more unique configurations are also possible. These include supporting alternate surround monitor
speaker systems or adding additional LFE or surround speakers. The monitor outputs are electronically balanced and designed
for connection to audio power amplifiers or amplified loudspeakers. Protection circuitry provides power-up and power-down
protection of the connected loudspeaker systems.
Audio input and output connections are made using four 25-pin D-subminiature connectors. The Model 74’s audio path
features low-noise, low-distortion analog switches for input source selection and laser-trimmed voltage-controlled-amplifier
(VCA) integrated circuits for monitor level control. One 9-pin D-subminiature connector is used to connect the Model 74 to the
Model 75 Control Console. A second 9-pin “D-sub” connector is used to interface remote control signals with the Model 74.
The Model 74’s talent amplifier output uses a 3-pin male XLR-type connector. An infrared receiver module can connect to the
Model 74 using a 3.5 mm jack.
An advanced 8-bit microcontroller provides the logic “horsepower” for the Model 74. AC mains power is connected directly to
the Model 74, which is factory selected for 100, 120, or 220/240 V operation. The internal power supply utilizes two toroidal
mains transformers for quiet audio operation.
Model 75 Control Console
The Model 75 Control Console is a compact, self-contained unit designed to be located at the operator’s position. It allows finger-
tip control of all monitoring and talkback parameters. Numerous LED indicators provide complete status information. A major
strength of the Model 75 is its ability to configure, under software control, many of the operating parameters. All configuration
parameters are stored in nonvolatile memory. The Model 75 Control Console connects to, and is powered by, the Model 74 Central
Controller. The Model 75 generates MIDI system-exclusive messages to control the Model 74. Remote-control signals connected
to the Model 74 Central Controller are routed to the Model 75 via pins in the 9-pin interconnecting cable.
The Model 75 provides four buttons and associated LEDs for selection of the surround and stereo sources to be monitored. While
in most cases only one input source will be monitored at a time, multiple inputs can be selected for simultaneous monitoring.
This allows two, three, or all four of the inputs to be combined (“summed”). While there is no independent control of the input
levels, this feature can be useful for creating rough mixes from the source signals. It is also a fast, effective means of making a
“seat-of-the-pants” check on the phase relationship between synchronized signals.
The monitor output levels are controlled using a large, easy-to-use rotary control. The “curve” or “taper” of the level control can
be configured to match an operator’s preference. The choices available are true logarithmic and modified logarithmic. The level
control auto mute all function allows the monitor output channels to mute automatically whenever the rotary level control is in
its fully counterclockwise (minimum) position. This is useful in applications such as on-air broadcast. By using the reference
level function, the monitor output level can be set to a pre-configured value. This is provided for audio-with-picture applications
that require a specific monitor level. The reference level is easily configured by taking an electronic “snapshot” of the position
of the rotary level control.
One button controls which monitor output, A or B, is active. For operator convenience, the dim function allows the monitor
output level to be reduced by a fixed dB amount. The dim level is configured from four available levels. A mute all function
allows all of the monitor output channels to be simultaneously muted. The mute/solo section provides individual output chan-
nel control. One pushbutton switch sets the operating mode for either mute or solo. In the mute mode, individual channels can