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StudioComm for Surround Sound
The StudioComm for
Surround Model 74 Central Controller and Model 75 Control Console work
together to provide 5.1 surround and stereo source monitoring
capabilities, along with a full-featured headphone “talkback” cue
system. The system is a perfect fit for contemporary facilities that
need to perform a variety of audio tasks. These can include surround and
stereo mixing and monitoring, live recording of voice, music, and sound
effects, and on-air broadcast applications. The system’s features were
carefully selected to provide extensive capabilities while remaining
simple to operate. Of overriding concern is maintaining the quality of
the connected audio sources. This is accomplished using a combination of
excellent circuit design and carefully selected components. The Model
74/Model 75 combination is ideal for adding surround monitoring
capability to disk-based recording systems. It’s also well suited for
upgrading a post-production or broadcast facility to support
multi-channel monitoring.
Overview
A complete StudioComm for
Surround 74/75 system begins with the Model 75 Control Console, a
compact user control surface that is intuitive and comfortable to use.
It is designed to reside at the operator’s location. The Model 75
connects to the Model 74 Central Controller using a single 9-pin cable.
Occupying one rack space, the Model 74 provides all audio input and
output circuitry, signal routing and control, and power supply
functions. To complete the system up to four
Model 35 Talent Amplifier
modules can be added. These connect to the Model 74 using standard 3-pin XLR-type audio cables. Model 35 units are typically deployed in
voice-over booths, studio areas, or other locations where voice or music
talent needs access to a headphone cue feed. Each unit provides a stereo
audio amplifier, user controls, and support for one or two pairs of
headphones.
Model 74 Central Controller
The Model
74 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 signals.
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 support 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 fingertip 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 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
operating mode.
Two
functions allow the format of the monitored sources to be checked for
level or phase inconsistencies. The 5.1 to stereo downmix function is
used to create a stereo signal from a 5.1 (surround) source. The stereo
to mono downmix function allows a stereo signal to be added (summed) and
monitored. The two downmix functions can be simultaneously enabled,
allowing a surround signal to be checked for mono compatibility. The
operating mode of the stereo to mono downmix function 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 stereo to mono downmix 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 simulated.
To
support the headphone cue system functions the Model 75 Control Console
includes three pushbutton switches and an integral microphone. As
expected, one button is used to enable the talkback function. The other
two buttons are used to set the talkback level over an 8-step range.
These buttons are also used to select which audio source is routed to
the headphones. Two choices are provided: the left and right channels of
the source selected for the monitor output, or the left and right
channels associated with Stereo B.
Typically
the talkback button contained in the Model 75 will be used to initiate
the talkback function. However, some applications may benefit from
having remote activation of talkback. The system provides several ways
of accomplishing this. In many cases the talkback button contained in
the Model 75 will be used to initiate the talkback function. However,
some applications may benefit from being able to remotely activate
talkback. A hard-wired signal can be connected to the remote talkback
input. In this way various types of external wired and wireless
equipment can be interfaced. An infrared (IR) receiver module can also
be directly connected. This allows the use of a wireless transmitter to
enable talkback. The microphone contained within the Model 75 Control
Console provides crisp, clear talkback audio. But some installations may
benefit from using an alternate source of talkback audio. This
capability is provided by the Model 74’s line-level talkback audio
input.
For
flexibility, the system is designed to easily integrate with recording
consoles, specialized playback systems, and audio-for-picture
machine-control electronics. Four hard-wired remote-control input
functions are provided: mute all, dim, talkback, and input select. By
providing access to the StudioComm’s mute all and dim functions,
talkback or slate activity from an audio console or other communications
system can control the monitor output level. The remote talkback input
allows an externally provided contact closure or logic signal to control
the talkback function. This allows easy integration with additional
wired or wireless talkback devices. The remote input select function is
provided expressly for audio post applications, allowing automatic
switching of the StudioComm’s input source whenever the mode of a
recording system changes between playback and record. This function,
referred historically as PEC/direct switching, allows accurate
monitoring during dialog replacement, Foley, or other overdub sessions.
Model
35 Talent Amplifier
In most cases
Model
35 Talent Amplifier modules will serve as the user’s headphone control
center. Each Model 35 contains amplifier circuitry, stereo level
control, mono switch, and two output jacks. For convenience, a
microphone mounting stand adapter is included with each Model 35. In
addition to the talent amplifier output, the Model 74 also provides a
stereo line-level cue output. This allows interfacing with other
headphone cue systems or could connect to a transmission system
associated with a remotely located studio or control room. The
line-level cue output can also serve as a source of “slate” audio for
workstations.
Specifications
Model 74 Central Controller
General Audio:
Frequency Response: 20 Hz-20 kHz ±0.1 dB (down 0.5 dB @ 60 kHz), monitor
outputs
Distortion (THD+N): 0.04%, measured at 1 kHz, +4 dBu, monitor outputs
S/N Ratio: 87 dB, ref +4 dBu out, 20 Hz-20 kHz, monitor outputs
Crosstalk: 78 dB, typical, ref +4 dBu in, 20 Hz-20 kHz, monitor outputs
Audio Inputs: 16, organized as two
6-channel “5.1” inputs and two 2-channel “stereo” inputs
Type: electronically balanced, compatible with balanced or unbalanced
sources
Impedance: 24 k ohms
Nominal Level: –12 dBV to +6 dBu, adjustable
Level Calibration: 15-turn trim potentiometers
Monitor Outputs: 2, 6-channel
Type: electronically balanced, compatible with balanced or unbalanced
loads
Maximum Level: +27 dBu into 10 k ohms, +26 dBu into 600 ohms
Talent Amplifier Output:
Compatibility: provides power and audio signals for up to four Model 35
Talent Amplifiers
Type: DC power with two channels of unbalanced audio
Connections: common on pin 1, DC (+27 volts nominal, 200 milliamperes
maximum) modulated with channel 1 audio (–10 dBu nominal) on pin 2, and
channel 2 audio (–10 dBu nominal) on pin 3
Line-Level Cue Output: 1, stereo
Nominal Level: +4 dBu, nominal
Type: electronically balanced, capacitor-coupled, intended to drive
balanced or unbalanced loads of 600 ohms or greater
Source Impedance: 100 ohms, nominal
Maximum Level: +20 dBu into 10 k ohms
Line-Level Talkback Input:
Level: +4 dBu, nominal
Type: electronically balanced
Impedance: 24 k ohms, nominal
Infrared Receiver Input:
Type: intended for use with industry-standard receiver module; data rate
650 baud
Remote Control Inputs: 4
Type: +5 volts DC logic, activates on closure to system common
Functions: mute, dim, talkback, input select
Downmix:
Functions: 5.1 to stereo, stereo to mono (mono-to-left-and-right,
mono-to-center)
5.1 to Stereo: LS @ –3 dB summed with L; RS @ –3 dB summed with R, C @
–6 dB summed with L and R; LS, RS, and LFE monitor outputs mute
Stereo to Mono (Mono-to-Left-and-Right): L summed with R to L and R or L
summed with R to C; attenuation independently configurable; C, LS, RS,
and LFE monitor outputs mute
Stereo to Mono (Mono-to-Center): L summed with R to C; attenuation
independently configurable; L, R, LS, RS, and LFE monitor outputs mute
Stereo to Mono (Mono-to-Center) Bandpass Filter:
Response: –3 dB @ 100 Hz and 5 kHz, nominal,
12 dB/octave
Connectors:
Audio: 4, 25-pin D-subminiature female
Talent Amplifier Output: 3-pin male XLR-type
To/From Model 75: 9-pin D-subminiature female
Remote Control Inputs: 9-pin D-subminiature female
Infrared Receiver Input: 3.5 mm 3-conductor jack
AC Mains: 3-blade, IEC 320 C14-compatible (mates with IEC 320 C13)
AC Mains Requirement:
100, 120, or 220/240 V, ±10%, factory configured, 50/60 Hz, 26 watts
maximum
Dimensions
(Overall):
19.00 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
9.58 inches deep (24.3 cm)
Mounting:
one space in a standard 19-inch rack
Weight:
9.5 pounds (4.3 kg)
Model 75 Control Console
Application: supports Model 74 Central Controller
Power: provided by Model 74 Central Controller
Output Data: generates MIDI system-exclusive messages
Connector: 9-pin D-subminiature female
Dimensions (Overall):
7.2 inches wide (18.3 cm)
2.2 inches high (5.6 cm)
5.4 inches deep (13.7 cm)
Weight: 1.8 pounds (0.82 kg)
Model
35 Talent
Amplifier
Load: intended for connection to one or two pairs of headphones
with total impedance of 75 ohms or greater
Maximum Output Voltage: 16 V peak-to-peak into 150 ohms @ 1% THD+Noise
Distortion (THD+N): 0.03%
Frequency Response: 20 Hz-20 kHz ±0.5 dB
Dimensions (Overall):
4.2 inches wide (10.7 cm)
2.0 inches high (5.1 cm)
5.3 inches deep (13.5 cm)
Weight: 0.8 pounds (0.7 kg)
Specifications
subject to change without notice.
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