Studio Technologies Model 68A/69A Surround Monitoring System Details
Surround Monitoring System with Analog I/O
As the production of
multi-channel "surround" audio material becomes prevalent, the need
for monitoring these sources becomes imperative for more and more facilities.
Studio Technologies has addressed this need with the StudioComm 68A 69A Surround
Monitoring System. The system is perfect for a variety of applications,
including adding "5.1" monitoring capability to disk-based recording
systems. It's also ideal for upgrading a post-production or broadcast facility
to support multi-channel monitoring. For the first time, multi-channel
monitoring features such as source selection, level control, and downmix are available
in an easy-to-use, cost-effective system.
The StudioComm 68A 69A
Surround Monitoring System is expressly designed to support 6-channel (5.1)
monitoring, with the channels designated as left, center, right, left surround,
right surround, and LFE. While it is anticipated that this channel arrangement
will be most common, the channels can obviously used in alternative
A StudioComm 68A 69A
Surround Monitoring System starts with the Model 69A Control Console, a compact
but comfortable "command center," that is designed to reside at the
operator's location. Using a single 9-pin cable, the Model 69A connects to the
Model 68A Central Controller. The Model 68A occupies just one rack space but
allows connection of two multi-channel inputs, two stereo inputs, along with
separate 6-channel and stereo monitor outputs. With the StudioComm 68A 69A
Surround Monitoring System any audio console, disk-based recording system, or
broadcast facility can have a complete multi-channel monitor system.
Model 68A Central Controller
The Model 68A Central
Controller is a single rack-space unit that contains analog, digital, and power
supply electronics. Four analog sources can be connected: two surround (5.1)
and two stereo. In many applications the first surround input, Surround A, will
be connected to a multi-channel output on an audio console or digital audio
workstation. The second surround input, Surround B, will be connected to a
playback device, such as a multitrack tape recorder or disk storage system. For
film or video post applications Surround A would be considered the direct
source, while Surround B would be considered the playback source.
The two stereo inputs,
Stereo A and Stereo B, are provided for general-purpose use and can be
connected to a variety of 2-channel direct and playback sources. For
flexibility, the surround and stereo inputs are compatible with balanced or
unbalanced signals having a nominal level range of -12 dBV to +6 dBu.
Fifteen-turn trim potentiometers are used to precisely calibrate the input
The Model 68A provides
separate monitor outputs to support both surround (5.1) and stereo loudspeaker
systems. The outputs are electronically balanced and designed for connection to
audio power amplifiers or amplified loudspeakers. Protection circuitry provides
power-up and power-down protection.
Audio input and output
connections are made using three 25-pin D-subminiature connectors. The Model
68A's audio path features analog switches for input source selection and
laser-trimmed voltage-controlled-amplifiers (VCA) for monitor level control.
One 9-pin D-subminiature connector is used to connect the Model 68A to the
Model 69A Control Console. A second 9-pin "D-sub" connector is used
to interface remote control signals with the Model 68A.
An 8-bit micro-controller
provides the logic "horsepower" for the Model 68A. AC mains power is
connected directly to the Model 68A, which is factory selected for 100, 120, or
220/240 V operation. The internal power supply utilizes a toroidal mains transformer
for quiet audio operation.
Model 69A Control Console
The Model 69A Control
Console is a compact, self-contained unit designed to be located at the
operator's position. It allows fingertip control of all monitoring parameters.
Numerous LED indicators provide complete status information. A major strength
of the Model 69A is its ability to configure, under software control, a number
of operating parameters. All configuration parameters are stored in
The Model 69A 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 surround and stereo
monitor output levels can be controlled by way of 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
allow the monitor output channels to automatically mute whenever the rotary
level control is in its fully counterclockwise (minimum) position. This is
useful in applications such as broadcast. By using the reference level
function, the monitor output level can 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.
For operator convenience,
the dim function allows the monitor output level to be reduced by a fixed dB
amount. The dim level is selected 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 channel control. One
pushbutton switch sets the operating mode for either mute or solo. In the mute
mode, individual channels can be muted as required. In the solo mode, one
channel can be monitored while the others are automatically muted. Depending on
the configuration, multiple channels can be simultaneously selected for
"soloing." The flexibility of having both mute and solo available
allows an operator to quickly select the most comfortable and productive
Two functions allow the
format of the monitored sources to be checked for level or phase
inconsistencies. The downmix function is used to create a stereo signal from a
surround (5.1) source. The mono function allows a stereo signal to be added
(summed) and monitored. The downmix and mono functions can be simultaneously
enabled, allowing a surround signal to be checked for mono compatibility. The
mono operating mode can be selected from two choices: mono-to-left-and-right or
mono-to-center. This allows support for both music and audio-with-picture
applications. A bandpass filter feature is associated with the mono function.
It is included to assist an operator in determining compatibility with
"real world" playback environments. A bandpass filter can be inserted
into the path of the mono signal, allowing the response of a monaural
loudspeaker associated with an inexpensive television or portable radio to be
The Model 69A Control
Console connects to, and is powered by, the Model 68A Central Controller using
a standard 9-pin D-subminiature cable. The Model 69A generates MIDI system-exclusive
messages to control the Model 68A. Remote-control signals connected to the
Model 68A Central Controller are routed to the Model 69A via pins in the 9-pin