Studio Technologies 761 User Manual
for Surround
Model 761 Central Controller and
Model 771 Control Console
User Guide
Issue 1, March 2008
This User Guide is applicable for systems consisting of:
Model 761: serial number M761-00151 and later with software version 1.02;
Model 771: M771-00151 and later
© 2008 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50226-0308, Issue 1
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for Surround
Table of Contents
Introduction ................................................................... 5
Installation .................................................................... 9
Confi guration ................................................................15
Operation ...................................................................... 29
Technical Notes ............................................................35
Specifi cations ...............................................................37
Appendix A ...................................................................38
Block Diagrams
Model 761 Central Controller
Model 771 Control Console
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Introduction
What This User Guide Covers
This User Guide is designed to assist you
when installing and using the Model 761
Central Controller and the Model 771
Control Console.
Overview
As production of both 5.1 surround and
2-channel stereo audio material becomes
a day-to-day reality, the need for monitoring these sources is imperative for broadcast and post-production facilities. Studio
Technologies has addressed this need with
the StudioComm for Surround Model 761
Central Controller and Model 771 Control
Console. While this system was designed
to support the needs of a major television network, it should fi nd a comfortable
home in many other applications as well.
About the only system features that were
selected to directly match this network’s requirements are related to the input source/
monitor output organization and naming
conventions. However this implementation
should match the needs of others too. With
its digital audio inputs, analog outputs, and
Dolby® E dialnorm support, it’s a simple
task to integrate the system into a variety
of facilities. The carefully selected feature
set provides the most-needed resources
and presents them in a way that remains
simple to use. In addition, by using the
best of contemporary technology, as well
as following rigorous design practices, the
system’s audio quality is simply excellent.
This version of the StudioComm for Surround system starts with the Model 771
Control Console, the “command center”
that is designed to reside at the operator’s
location. It allows fi ngertip selection of
all monitoring functions. Numerous LED
indicators provide complete status information. A 4-digit numeric display indicates
the monitor output or dialnorm level in real
time. A major strength of the Model 771
is its ability to confi gure, under software
control, a number of operating parameters.
Using a 9-pin cable, the Model 771 connects to a Model 761 Central Controller.
The Model 761 Central Controller occupies
just one rack space but allows connection of two 5.1 surround inputs and three
2-channel stereo inputs. In addition, a 5.1
surround and special 2-channel stereo “director cue” monitor output are provided.
All the 5.1 and stereo inputs are digital
and are compatible with AES3id sources.
These unbalanced digital signals utilize
BNC connectors and are ubiquitous in
most broadcast and many post-production
environments. Sample rates of up to 192
kHz and bit depths of up to 24 are supported. With the system’s dynamic range of
greater than 106 dB, there isn’t a problem
ensuring that the quality of all connected
audio sources is maintained. The monitor
outputs are analog, balanced line level,
and have a maximum level of +26 dBu.
They include power-up/power-down protection circuitry to help maintain the health
of the connected loudspeaker systems.
A source of Dolby E metadata can be
connected to the Model 761 Central Controller. This RS-485/RS-422 115.2 kbit/s
compatible signal carries numerous data
elements, including one that represents
the average dialog level of an associated
audio program. This dialog normalization
or “dialnorm” value is an integral part of
many broadcast distribution systems, ending up in the audio playback systems of
consumers. Hardware and software within
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the Model 761 separates out the dialnorm
element that relates to one of the connected 5.1 surround audio sources. This
dialnorm level value can then be displayed
on the Model 771 Control Console, as
well as used to automatically adjust the
monitor output level. This provides a
unique solution to the broadcast and postproduction world, allowing a professional
environment to accurately simulate an end
user’s experience.
Digital audio sources are interfaced with
the Model 761 using nine BNC connectors.
Analog monitor output signal connections
are made using one 25-pin D-subminiature connector. One 9-pin D-subminiature
connector is used to link the Model 761 to
the Model 771 Control Console. A second
9-pin D-sub connector is used to interface
metadata and remote control signals with
the Model 761. An advanced fl ash-based
microcontroller integrated circuit provides
the logic “horsepower” for the unit. AC
mains power is connected directly to
the Model 761, 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.
Additional Details
The Model 771 provides four buttons
and associated LEDs for selection of the
input source to be monitored. A total of
six sources can be monitored, one being
active at a time. Two of the sources are 5.1
surround, while the other four are monaural. For fl exibility, one of the 5.1 inputs can
be confi gured to be directly compatible
with a 2-channel stereo source.
Figure 1. Model 761 Central Controller Front Panel
Figure 2. Model 761 Central Controller Back Panel
AC mains
input connection
To/from
Model 771
Control
Console
RS-485 and
remote control
inputs
Analog monitor
output connections
Stereo Input C
connection
Surround Input B
connections
Control console
to/from data
active LED
Surround Input A
connections
Metadata
active
LED
Stereo Input A and
Stereo Input B
connections
Powe r
present
LED
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Director cue
output enable
for Surround
Channel solo
Downmix
Input select
Figure 3. Model 771 Control Console Front Panel
The 5.1 monitor output levels can be
controlled by way of a large, easy-to-use
rotary control. The level control auto
mute all function ensures the monitor
output channels automatically mute whenever the rotary level control is in its fully
counterclockwise (minimum) position.
By using the reference level function,
the monitor output level can be set to a
pre-confi gured value. This is provided
for audio-with-picture applications which
require a specifi c monitor level. The reference level is easily confi gured by taking an
electronic “snapshot” of the position of the
rotary level control. For operator confi rmation, a 4-digit LED display shows the level
of the monitor output. The display can be
confi gured for either an attenuation mode
or a direct db SPL value.
The dim function allows the monitor output
level to be reduced by a fi xed dB amount.
The dim level is selected from four available levels. A mute all function allows all
Display mode
Dialnorm and
monitor output
level display
Monitor Output
• Dialnorm enable
• Reference level
• Mute all
• Dim
• Rotary level control
monitor output channels to be simultaneously muted. The channel solo function
allows one or more specifi c channels to
be monitored while the others are automatically muted.
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 the selected 5.1 surround source. The stereo to mono downmix function allows audio on the left and
right channels to be added (summed) and
monitored on the monitor’s system’s center
channel. The two downmix functions can
be simultaneously enabled, allowing a 5.1
surround source to be checked for mono
compatibility.
A special “director cue” output function
is provided. This allows a monaural or
stereo input to be connected to the Model
761 Central Controller, which also has
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a dedicated 2-channel stereo output associated with it. A button on the Model
771 Control Console allows on/off control
of this signal. This is useful when control
rooms need to monitor auxiliary audio
signals, such as site-event cue signals,
through an independent set of loudspeakers. For additional fl exibility, two remote
control input functions are provided: mute
all and dim. By providing access to these
functions, talkback or communications
activity from an audio console or matrix
intercom system can control the level of
the system’s 5.1 monitor outputs.
The Model 771 Control Console connects
to, and is powered by, the Model 761 Central Controller. The interconnecting cable
uses 9-pin D-subminiature connectors and
carries RS-485 data and DC power. The
Dolby E-compatible metadata connects to
the Model 761 by way of a second 9-pin
D-sub connector. Remote control signals,
including mute all and dim, also connect
to the Model 771 using the second 9-pin
D-sub connector.
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Installation
In this section you will be installing the
Model 761 Central Controller in an equipment rack. Connections to the digital audio
inputs and analog monitor outputs will be
made. A location will be selected for the
Model 771 Control Console and it will be
connected to the Model 761. If applicable,
a source of Dolby E metadata may be connected. In addition, external equipment will
be interfaced to the remote control inputs.
AC mains power will be connected to the
Model 761.
System Components
The shipping carton contains one each
of the following: Model 761 Central Controller, Model 771 Control Console, 20-foot
(6.1 m) 9-pin D-sub interconnecting cable,
and user guide. Units destined for North
America also include an AC mains cord.
Your dealer or distributor should provide an
AC mains cord for destinations outside of
North American.
Mounting the Model 761
The Model 761 Central Controller requires
one space in a standard 19-inch (48.3 cm)
equipment rack. Select a location that is
convenient for making connections to the
digital and analog audio signals as well
as to the Model 771 Control Console. A
20-foot (6.1 m) cable is supplied to connect the Model 761 to the Model 771. If the
needs of a specifi c installation dictate, an
alternate-length interconnecting cable can
be fabricated and used. Secure the Model
761 into the equipment rack using two
mounting screws per side.
Audio Connections
Audio signal connections are made by
way of multiple BNC jacks and a 25-pin
D-subminiature connector which are
located on the Model 761’s back panel.
Refer to Figure 2 for a detailed view of the
back panel. The BNC jacks will be used
for the digital audio signals. A cable assembly with a 25-pin D-sub plug (male) on
one end and the desired connectors on the
other end will be used for connecting to the
analog monitor outputs.
Digital Audio Inputs
The nine female BNC connectors on the
Model 761’s back panel are used to interface with digital audio signal sources.
Please refer to Figure 4 for details on the
supported inputs and the exact connectors
to be used.
Note that the input source titles in Figure 4
refer to the button selections on the Model
771 Control Console. It includes support
for three input sources each for both SD
(standard-defi nition) and HD (high-defi nition) programming. For SD the primary
source is either 5.1 surround or 2-channel
stereo while for HD the primary source
is intended to be 5.1 surround. In both
SD and HD the SAP (secondary audio
program) and INTL (international) inputs
are monaural. Of course, technically, all
the digital audio inputs on the Model 761
provide the same excellent audio quality.
The titles refer only to the intended signal
sources.
Each of the available digital audio inputs
is intended for connection to an unbalanced digital audio source that is compatible with the AES3id-2001 standard. In
broadcast environments these signals may
also be referred to as following the SMPTE
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SD–Primary
This input selection allows a 5.1 surround or 2-channel stereo audio source to be monitored.
Left Source: Channel 1, Surround A L/R input
Right Source: Channel 2, Surround A L/R input
Center Source: Channel 1, Surround A C/LFE input
LFE Source: Channel 2, Surround A C/LFE input
LS Source: Channel 1, Surround A LS/RS input
RS Source: Channel 2, Surround A LS/RS input
SD–SAP
This input selection allows a mono audio source to be monitored.
Source: Channel 1, Stereo A L/R input
SD–INTL
This input selection allows a mono audio source to be monitored.
Source: Channel 2, Stereo A L/R input
HD–Primary
This input selection allows a 5.1 surround audio source to be monitored.
Left Source: Channel 1, Surround B L/R input
Right Source: Channel 2, Surround B L/R input
Center Source: Channel 1, Surround B C/LFE input
LFE Source: Channel 2, Surround B C/LFE input
LS Source: Channel 1, Surround B LS/RS input
RS Source: Channel 2, Surround B LS/RS input
HD–SAP
This input selection allows a mono audio source to be monitored.
Source: Channel 1, Stereo B L/R input
HD–INTL
This input selection allows a mono audio source to be monitored.
Source: Channel 2, Stereo B L/R input
Director Cue
This input selection allows a 2-channel stereo audio source to be monitored using separate analog outputs.
L Source: Channel 1, Stereo C L/R input
R Source: Channel 2, Stereo C L/R input
Figure 4. Model 761 Digital Audio Inputs
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276M standard. As expected, these signal
sources will be provided in the form of
coaxial cables with BNC plugs attached.
The Model 761 supports sampling rates
of up to 192 kHz with a word length (bit
depth) of up to 24. Note that no external
synchronization source is required as the
inputs are all self-clocking.
Balanced AES3 digital audio signals can
also be used with the Model 761’s inputs
so long as external coupling transformers
(“baluns”) are utilized. These impedancematching (110 ohms to 75 ohms) transformer assemblies typically use a 3-pin
female XLR connector on their input and
a female BNC connector on their output.
Monitor Outputs
The connector labeled Analog Monitor
Outputs provides access to the Model
761’s 5.1 surround and 2-channel stereo
director cue monitor outputs. The surround
output channels are intended to connect
to the main surround loudspeaker system
incorporated in a facility. The director
cue output channels are provided to
support a separate set of loudspeakers,
allowing monitoring of inter- or intra-facility
communications.
The monitor output channels are intended
for connection to audio amplifi ers associated with monitor loudspeakers, or to the
inputs of loudspeakers that contain integrated amplifi ers. The monitor outputs are
electronically balanced and capable of
driving balanced or unbalanced loads of
600 ohms or greater. While balanced operation is preferred, unbalanced operation
does not pose a problem. To connect to
an unbalanced load connect the + terminal
as signal high, and both the – and shield
as the signal low/shield. For optimal unbalanced operation, it is important to connect
both – and shield together directly on the
D-sub plug, not at the other end of the
harness.
Note that while the Model 761’s electronically balanced output circuits are capable
of driving loads of 600 ohms or greater,
the output level will drop slightly as the
load impedance approaches 600 ohms.
A 0.5 dB difference in output level can be
expected as the load impedance changes
from 10 k ohms to 600 ohms.
The wiring scheme used by the D-subminiature connector complies with that
made popular by TASCAM® with their
DA-88® product. A wiring assembly prepared for the Model 761’s monitor outputs
is identical to that of a DA-88-style output
assembly. Please refer to Figure 5 for the
exact connection details. Note that unlike
a DA-88-style assembly, the Model 761’s
D-sub connector uses 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
Signal Signal
Connections High (+) Low (–) Shield
L 24 12 25
R 10 23 11
C 21 9 22
LFE 7 20 8
LS 18 6 19
RS 4 17 5
Director Cue L 15 3 16
Director Cue R 1 14 2
Notes: 1) Connector type on Model 761 is 25-pin D-subminiature
female. Installer must provide plug (male). Connector uses
4-40 threaded inserts for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-type wiring harnesses are directly
compatible, with the exception of 4-40 screw threads
being required.
Figure 5. Connections for Monitor and Director
Cue Outputs
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Metadata Input
The Model 761 allows a source of Dolby E
metadata to be directly connected. Hardware and software inside the Model 761
extracts (“parses”) a dialnorm data element from the connected metadata signal.
This dialnorm value can then be viewed
on the Model 771 and, if desired, used to
control the monitor output levels. Refer to
the Technical Notes section of this guide
for details.
The metadata must be in the form of an
RS-485 or RS-422 asynchronous serial
signal. This differential signal must have
a data rate of 115.2 kbit/s and a data format of 8 data bits, no parity, and 1 stop
bit (8-N-1). A metadata signal of this type
is commonly available on metadatagenerating or de-embedding equipment
from broadcast equipment manufacturers
such as Dolby Laboratories, Evertz, and
NVISION.
While technically the Model 761’s RS-485
connection is bi-directional, in software
it’s confi gured to only receive data. This
means that there’s no reason why a signal
already connected between two pieces of
equipment can’t be connected in parallel
(“bridged”) with the Model 761’s metadata
input. Refer to Figure 6 for exact connection details. While only the data+ and data–
connections are absolutely necessary,
a shield connection can also be made.
Note that the connections for the metadata
signal are reminiscent of the SMPTE 207M
standard.
Note that Studio Technologies has found
documentation supplied with some metadata-generating equipment has incorrect
pin-out information. This resulted in much
head scratching and hair pulling. As such,
it may be valuable to use a logic analyzer
Signal Pin Direction
RS-485 Data+ 7 Input
RS-485 Data– 2 Input
Data Shield 1 Shield
Remote Mute All 5 Input
Remote Dim 6 Input
Remote Spare 1 8 Input
Remote Spare 2 9 Input
Remote Input Common 4 Common
Note: Connector type on Model 761 is 9-pin D-subminiature
female. Connector uses 4-40 threaded inserts for
locking with mating plug.
Figure 6. Connector Pin Out for Metadata Input
and Remote Control Inputs
or oscilloscope to confi rm that the metadata source is terminated as expected
prior to connecting it to the Model 761.
Remote Control Inputs
Support is provided for two remote control input functions: remote mute all and
remote dim. The inputs use logic gates,
“pulled up” to +5 V by way of resistors,
which are active whenever they are
brought to their logic low state. Inputs of
this type are commonly referred to as GPI
inputs. While the input circuitry is protected
from over-current and static (ESD) discharge, care should be taken to prevent
nasty signals from reaching them. The
inputs are active only when held in the low
state; they can’t be confi gured to change
state (“latch”) in response to a logic pulse.
A 9-pin female D-subminiature connector
is used to interface with the remote control
inputs. This connector, labeled RS-485/
Remote Control Inputs, is located on the
back panel of the Model 761. Refer to
Figure 6 for exact connection details. Note
that pin 4 (remote input common) connects
to the Model 761’s internal circuit com-
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mon connection as well as the Model 761’s
chassis and mains earth connection. The
two spare inputs are provided for future
special applications. As such, pins 8 and 9
should remain unconnected.
Connecting the Model 761
to the Model 771
A 9-pin female D-subminiature connector,
labeled To/From Control Console, is provided on the back panel of the Model 761
Central Controller. Another 9-pin D-sub
connector, labeled To/From Central Controller, is provided on the back panel of
the Model 771 Control Console. A cable
with 9-pin male D-sub connectors on each
end is used to interconnect the two units. A
20-foot (6.1-meter) cable is included in the
shipping carton of each system. This cable
implements all nine connector pins in a
one-to-one manner.
Should an interconnecting cable of a
different length be required there’s no
problem for one to be fabricated and used.
While it can be wired in a one-to-one fashion covering all nine pins, a minimum of
only four connections are required: data+,
data–, DC+, and DC–. The Model 761’s
connector pin-out scheme was designed
to allow creation of an interconnecting
cable which uses commonly available twopair audio cable. This cable, consisting of
two twisted pairs each with an individual
shield, is often sleek, fl exible, and available
in many colors. One pair and shield can
be used for the data connections and the
other pair and shield can be used for the
DC connections. This implementation has
the advantages of providing a shield for
the data path and a more robust common
connection (two conductors including the
shield) for the DC power circuit. Refer
to Figure 7 for details.
It’s hard to specify a maximum interconnecting cable length. The data connections
won’t be the limiting factor as the differential transmission scheme of an RS-485
interface makes an interconnection in
excess of 1000 feet (300+ meters) easily possible. The culprit is the DC current
supplied by the Model 761 to power the
Model 771. This nominal 12 volt DC, 100
milliamperes maximum signal is subject
to the resistive voltage losses associated
with the interconnecting cable. For correct
Model 771 performance the voltage supplied to the Model 771, when measured
directly at the Model 771’s 9-pin connector
and at full load, must be 9 volts minimum.
This requires that the voltage drop due to
the interconnecting cable be no more than
3 volts DC. Using Ohm’s law, it’s quite easy
to determine whether the selected cable
will support the desired interconnection
length. To calculate the voltage drop, multiply the total resistance (in ohms) of the
proposed cable by 0.01 (the square of the
maximum current). Remember to include
the resistance in both the DC– and DC+
wires.
Signal Pin Direction
Data+ 1 To/From Model 771
Data– 6 To/From Model 771
Data Shield 2 To/From Model 771
DC+ 4 To Model 771
DC– 9 To Model 771
DC Power Shield 5 To/From Model 771
Note: Connector type on Model 761 is 9-pin D-subminiature
female. Connector uses 4-40 threaded inserts for
locking with mating plug.
Figure 7. Connections between Model 761 and
Model 771
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