for Surround Model 760-01 Central Controller and Model 77 Control Console User Guide

for Surround Model 760-01 Central Controller and Model 77 Control Console User Guide
for Surround
Model 760-01 Central Controller and
Model 77 Control Console
User Guide
Issue 3, April 2015
This User Guide is applicable for systems consisting of:
Model 760-01: serial number M760-01-00151 and later with
software version 4.40 and higher and FPGA version 4.15 and higher;
Model 77: serial number M77-00151 and later with software version 4.40 and higher
© 2015 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50245-0415, Issue 3
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for Surround
Table of Contents
Revision History............................................................ 4
Introduction ................................................................... 5
Installation .................................................................... 9
Configuration ................................................................16
Operation ......................................................................37
Technical Notes ............................................................44
Specifications ...............................................................48
Appendix A—Connection Pin-Out Charts ....................50
Appendix B—Sync Input Sources ................................51
Appendix C—Downmix Formulas .................................52
Model 760-01/77 User Guide
Studio Technologies, Inc.
Issue 3, April 2015
Page 3
for Surround
Revision History
Issue 3, April 2015:
1. Revised specifications to reflect final audio performance measurements.
Issue 2, January 2015:
1. Text clarifications.
2. Reflects final product nomenclature (Model 760-01/Model 77).
Issue 1, May 2014:
1. Initial release (as Model 76D-110/Model 77).
Issue 3, April 2015
Page 4
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Introduction
What This User Guide Covers
This User Guide is designed to assist you
when installing and using the Model 760-01
Central Controller and one or more associated Model 77 or Model 71 Control Consoles.
Overview
As creating and distributing multi-channel
surround (5.1) and stereo audio material has
become a day-to-day reality, the ability to
simply and effectively monitor these sources
is imperative for recording, post-production,
and broadcast facilities. And with audio-withpicture applications becoming so prevalent,
additional monitoring challenges have arisen.
Studio Technologies has addressed these
needs with the StudioComm for Surround
Model 760-01 Central Controller and the
Model 77 and Model 71 Control Consoles.
With digital audio inputs, digital monitor
outputs, support for multiple user control
surfaces, and an extensive set of operating resources it’s a simple task to integrate
a monitoring system into virtually any facility. The carefully selected group of features,
including surround and stereo inputs, configurable input-signal time delay, multiple
pre- and post-fader outputs, configurable
downmix and mute/solo functions, and bass
management, along with a multi-format sync
input, make the system powerful yet simple
to operate. And by using the best of contemporary technology, as well as following
rigorous design practices, the system’s audio
quality is excellent.
A StudioComm for Surround system starts
with the Model 77 Control Console. It’s the
system’s “command center” and is designed
to reside at a user’s location, allowing fingertip selection of all monitoring functions.
Model 760-01/77 User Guide
Studio Technologies, Inc.
Numerous LED indicators provide complete status information. A 4-digit numeric
display indicates the post-fader monitor
output level in real time. A major strength
of the Model 77 is its ability to configure,
under software control, many important
operating parameters. Intended for secondary monitoring locations, the Model 71
Control Console is a compact user control
surface. It provides three of the most basic
functions: a rotary level control, dim on/off
button, and reference level on/off button.
Most installations will use only one Model
77 Control Console. However, up to three
additional Model 77 or Model 71 Control
Consoles can also be connected. This
provides multiple users with full control
over a facility’s monitor system. And to
make installation simple, the Model 760-01
provides power for all connected Model 77
or Model 71 units.
The core of this StudioComm for Surround
system is the Model 760-01 Central Controller. The one-rack-space unit contains
circuitry that supports balanced digital
audio inputs, balanced digital monitor
outputs, digital audio and control processing, and interfacing for the user control
surface(s). The Model 760-01 provides
two surround (5.1) and three stereo digital
audio inputs. These balanced digital inputs
are AES3-compliant; sources of this type
are ubiquitous in many post-production
and audio facility environments. The inputs allow a sample rate of up to 192 kHz
and a bit depth of up to 24 to be directly
supported. Circuitry associated with one
of the stereo inputs provides sample rate
conversion (SRC) capability, allowing a
wide range of digital audio sources to be
monitored. Up to 340 milliseconds of input
delay can be selected to compensate for
processing delays in an associated video
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for Surround
path. For flexibility, two delay values can be
configured, allowing real-time selection as
desired. A number of different signals can
serve as the Model 760-01’s digital audio
timing reference. For synchronization with a
master timing reference a dedicated source
of word clock, DARS (AES11), bi-level
video, or tri-level video can be connected.
Alternately, the L/R connection of the actively selected surround or stereo input
source can serve as the timing reference.
signals with an output impedance of
110 ohms and a signal level of 5 volts
peak-to-peak (Vpp).
A sophisticated bass management function is integral to the Model 760-01’s design
and can be enabled if desired. Note however that the bass management function is
only supported at sample rates of 44.1, 48,
88.2, and 96 kHz. The overall goal of bass
management is very simple: ensure that the
entire audio bandwidth of all channels can
be accurately monitored. Many loudspeaker
systems have inherent low-frequency
limitations, preventing a true picture of the
source material from being presented. To
overcome this, the low-frequency energy
from the five channels associated with the
surround inputs and the two channels associated with the stereo inputs can be separated and routed to the subwoofer (SUB)
channel of the monitor outputs. Several of
the bass management functions can be
configured to match the requirements of
specific installations.
A range of surround (5.1) and stereo digital
monitor outputs are provided. The post-fader surround and stereo monitor outputs are
intended for connection to monitor loudspeaker systems. The pre-fader surround
monitor output can be used with metering
systems that require signals that aren’t impacted by level control or other monitoring
functions. The stereo input C direct monitor output allows an installation to directly
access the SRC capabilities. The monitor
outputs are compatible with equipment
that requires balanced AES3 digital audio
Figure 1. Model 760-01 Central Controller Front Panel
Control console
status LED
Sync status
LED
Figure 2. Model 760-01 Central Controller Back Panel
AC mains input
To/from
Models 77 &
71 Control
Consoles
Digital
monitor outputs
Sync
input
Stereo
input C
Digital surround (5.1 ) inputs A & B
and digital stereo inputs A & B
Remote control inputs
Issue 3, April 2015
Page 6
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Channel mute/solo
Mute/solo
mode
Downmix
Input source
select
Monitor output
level display
Post-fader surround
monitor output
• Surround/stereo
• Reference level
• Mute all
• Dim
• Rotary level control
Figure 3. Model 77 Control Console Front Panel
Great care was taken in designing the
system’s architecture, ensuring that the
character of the audio input signals is
preserved. All audio processing, including
bass management, is performed in 32-bit
logic using a high-speed field-programmable gate array (FPGA) integrated circuit.
The Model 760-01 occupies one space
(1U) in a standard 19-inch rack. Digital
audio sources are interfaced with the
Model 760-01 using one 25-pin female
D-subminiature connector and one 3-pin
female XLR connector. A BNC connector
is used to interface with an external sync
source. Digital monitor output signal connections are made using a 25-pin female
D-subminiature connector. One 9-pin
female D-subminiature connector is used
to connect the Model 760-01 with a maximum of four Model 77 or Model 71 Control
Consoles. A second 9-pin “D-sub” connector is used to interface with remote control
signals. AC mains power is connected directly to the Model 760-01, with an acceptable range of 100 to 240 V, 50/60 Hz.
Model 760-01/77 User Guide
Studio Technologies, Inc.
Additional Details
The Model 77 provides five buttons and
associated LEDs for selection of the surround and stereo input sources to be monitored. While in most cases only one input
source will be monitored at a time, stereo
input C can be selected for simultaneous
monitoring with one of the two surround
or other two stereo inputs. This allows
the two selected inputs to be combined
(“summed”).
It’s interesting to note that while each of
the two surround inputs has an LFE channel associated with it, the “.1” post-fader
surround monitor output is designated as
SUB (subwoofer), rather than LFE. This
terminology was carefully selected to highlight the fact that this output channel may
include more than just LFE content. The
bass management function, if enabled,
will redirect low-frequency energy from the
main input channels, combining it with the
LFE content before routing the sum to the
subwoofer output.
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The post-fader surround and stereo monitor
output levels can be controlled by way of a
large, easy-to-use rotary control. The control, actually a digital encoder, allows level
selection in precise 0.5-dB steps. The auto
mute all function causes the post-fader surround and stereo monitor output channels
to automatically mute whenever the output
level control reaches maximum attenuation. Using the reference level function, the
post-fader surround and stereo monitor
output levels can be set to a pre-configured
value. This is provided for audio-with-picture
applications that require a specific monitor
output level. The reference level is easily
configured by taking an electronic “snapshot” of the desired monitor output level.
For user confirmation a 4-digit LED readout
can display the level of the post-fader surround and stereo monitor output channels.
To match the needs of a facility, it can be
configured to display either the attenuation
level or the sound pressure level (SPL).
The dim function allows the post-fader surround and stereo monitor output levels to be
reduced by a fixed dB amount. The dim level
is configured from among four available
values. A mute all function allows the postfader surround and stereo monitor output
channels to be simultaneously muted. The
channel mute/solo section provides postfader surround and stereo channel monitoring control, allowing a single channel to be
muted or monitored. Multiple channels can
also be simultaneously selected for muting
or “soloing.”
A special solo mode is also provided, called
channel pop solo, which offers a unique
aid when monitoring audio material. Channel pop solo allows the level of a single
post-fader monitor output channel to be
raised while the level of the other channels
is reduced. This helps to emphasize the
Issue 3, April 2015
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content on one channel without fully muting the others. Broadcast applications can
benefit from the channel pop solo mode by
allowing, for example, the center channel to
be highlighted while still maintaining some
level on the other channels. The amount of
level increase—the “pop”—as well as the
amount of attenuation can be configured to
meet the needs of specific applications or
users.
Two functions allow the input sources to be
checked for level or phase inconsistencies.
The surround to stereo downmix function is
used to create a stereo signal from the selected surround (5.1) source. Key operating
parameters in the surround to stereo downmix function can be configured to meet the
requirements of an application. This can be
especially useful when support for specific
international broadcast standards is required. The stereo to mono downmix function allows audio on the left and right input
channels to be added (summed) and monitored on the center output channel. The two
downmix functions can be simultaneously
enabled, allowing a surround source to be
checked for mono compatibility. The downmix functions always impact the post-fader
surround and stereo monitor outputs. A
configuration setting allows the pre-fader
surround monitor output to be selected for
pre- or post-downmix operation.
For flexibility, the StudioComm for Surround
system is designed to easily integrate with
equipment such as production intercom
systems, on-air or recording tally signals,
and audio consoles. Two remote-control
inputs provide access to the mute all and
dim functions. By providing access to these
functions, talkback or slate activity from an
audio console or other communications
system can control the level of the postfader surround and stereo monitor outputs.
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Installation
In this section you will be installing the
Model 760-01 Central Controller in an
equipment rack. Connections to the digital
audio inputs and digital monitor outputs will
be made. A dedicated digital audio timing
reference signal can be connected to the
sync input. If desired, external equipment
will be interfaced to the remote control
inputs. A location will be selected for the
first Model 77 Control Console and it will
be connected to the Model 760-01. AC
mains power will be connected to the
Model 760-01. For advanced applications
up to three additional Model 77 or Model
71 Control Console units can be connected to the Model 760-01.
System Components
The main shipping carton contains one
each of the following: Model 760-01 Central Controller, Model 77 Control Console,
9-pin D-sub interconnecting cable, and
user guide. Also included in the shipping carton is a North-American-standard
AC mains cord. Your dealer or distributor
should provide an AC mains cord appropriate for destinations outside of North
America. Any additional Model 77 or Model
71 Control Consoles will be shipped in
separate cartons.
Mounting the Model 760-01
The Model 760-01 Central Controller
requires one space (1U) in a standard
19-inch (48.3 cm) equipment rack. Secure
the Model 760-01 into the equipment rack
using two mounting screws per side. Select a location that is convenient for making
connections to the audio signals as well
as interfacing with the first (or only) Model
77 Control Console. A cable is supplied
Model 760-01/77 User Guide
Studio Technologies, Inc.
to connect the Model 760-01 to the Model
77. If the needs of a specific installation
dictate, an alternate-length interconnecting
cable can be fabricated and used.
Audio Connections
Audio connections are made by way of two
25-pin female D-subminiature connectors
and one 3-pin female XLR connector. All
the connectors are located on the Model
760-01’s back panel. Refer to Figure 2 for
a detailed view of these connectors.
Audio Inputs
Two surround (5.1) and three stereo digital
audio sources can be connected. All sources can be monitored using the pre- and
post-fader surround and post-fader stereo
monitor output channels. A one-to-one relationship is maintained between the input
and output channels, i.e., left input to left
monitor output, right input to right monitor output, center input to center monitor
output, etc. (Of course this won’t be true in
the case where the user has enabled one
or both of the downmix functions.) Stereo
input C is also routed to the stereo input C
direct monitor output.
The audio inputs support digital audio signals with a sampling rate of up to 192 kHz
and a word length (depth) of up to 24 bits.
It’s best if the connected signal sources
maintain a common sample rate and timing reference. Having all signals “locked”
together helps to ensure proper handling
by the Model 760-01’s all-digital signal
control path.
There is, however, an exception worth noting. Circuitry associated with stereo input
C has sample rate conversion (SRC) capability, allowing virtually any digital audio
signal to be connected. A signal connected
Issue 3, April 2015
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for Surround
to stereo input C can have an independent
sample rate and timing reference and still
be monitored correctly. Refer to the Technical Notes section of this user guide for a
detailed review of the SRC capability.
The Model 760-01’s digital audio inputs
are intended for connection with balanced
digital audio sources that are compatible
with the AES3 standard. This signal type
has a nominal impedance of 110 ohms and
a nominal signal level of 5 Vpp.
One 25-pin female D-subminiature connector (DB-25F) is used to interface with the 16
channels associated with surround input A,
surround input B, stereo input A, and stereo
input B. Each of the eight physical connections supports two audio channels. Often a
wiring assembly prepared for these digital
audio inputs would typically be identical to
that of a TASCAM-type (AES59-compliant)
input assembly. An assembly of this type
would have eight 3-pin female XLR connectors on one end and a 25-pin male D-subminiature connector (DB-25M) on the other.
Refer to Figure 4 for details on connecting
with the 25-pin female D-subminiature
connector.
On the Model 760-01 stereo input C uses a
3-pin female XLR connector for interfacing
with a digital audio signal source. The mating cable should have a 3-pin XLR connector wired such that signal + goes to pin 2,
the – signal to pin 3, and shield to pin 1.
Unbalanced AES3 digital audio signals can
also be used with the Model 760-01’s inputs
if external coupling transformers (“baluns”)
are utilized. These impedance-matching
(75 ohms to 110 ohms) and level step-up
transformer assemblies typically provide a
BNC connector on their input and a 3-pin
male XLR connector on their output.
Issue 3, April 2015
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Channel
Signal
High (+)
Signal
Low (–)
Shield
Surround Input A L/R
1
24
12
25
Surround Input A C/LFE
2
10
23
11
Surround Input A LS/RS
3
21
9
22
Stereo Input A
4
7
20
8
Surround Input B L/R
5
18
6
19
Surround Input B C/LFE
6
4
17
5
Surround Input B LS/RS
7
15
3
16
Stereo Input B
8
1
14
2
Connections
Notes: 1) All signals transformer-coupled digital audio;
balanced AES3 (110 ohms, 5 Vpp) compatible.
2) Connector type on Model 760-01 is 25-pin female
D-subminiature (DB-25F). Installer must provide male
(DB-25M). Connector uses 4-40 threaded inserts for
locking with mating plug.
3) Wiring scheme follows AES59-2012 convention.
Standard TASCAM-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Figure 4. Connections for Surround A,
Surround B, Stereo A, and Stereo B Digital Inputs
Monitor Outputs
The 25-pin female D-subminiature connector labeled Digital Monitor Outputs provides
access to the Model 760-01’s 16 channels
of digital audio monitor output: pre-fader
surround, post-fader surround, post-fader
stereo, and stereo input C direct. The prefader surround monitor output channels
are intended for connection to metering or
monitoring equipment that requires uninterrupted full-level signals.
The post-fader surround monitor output
channels are intended to connect to a 5.1
loudspeaker system. The post-fader stereo
monitor output is provided to support a separate set of stereo monitor loudspeakers.
The stereo input C direct monitor output is
essentially a unity gain copy of the signal
connected to stereo input C. However, the
signal does pass through the sample rate
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
conversion (SRC) and input delay circuitry.
The impact made by these functions will
depend on the specific input signal and the
Model 760-01’s configuration settings.
The monitor outputs are transformercoupled balanced AES3 digital audio
signals with a source impedance of 110
ohms and a nominal signal level of 5 Vpp.
Signals of this type are normally interconnected to destination equipment using
shielded twisted-pair cable terminated
with 3-pin male XLR connectors.
A cable assembly with a 25-pin male
D-subminiature connector (DB-25M) on
one end and the desired connectors on the
other end will be used for connecting to
the digital monitor outputs. The D-subminiature connector follows the TASCAM®type (AES59-compliant) wiring convention,
organizing the 25 pins into eight groups of
three pins each; one pin remains unused.
Each set of three pins provides an independent interface. In the analog world this
would allow eight audio signals to be transported. But with AES3 digital audio signals
this allows support for 16 audio channels;
eight interfaces each supplying two audio
channels.
pin 2 of the XLR, the – terminal to XLR pin
3, and the shield terminal to XLR pin 1. Refer to Figure 5 or Appendix A for the exact
connection details. Note that unlike a TASCAM-type assembly, the two threaded fasteners associated with the Model 760-01’s
D-sub connectors use 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
Connections
Channel
Signal
High (+)
Signal
Low (–)
Shield
Pre-Fader L/R
1
24
12
25
Pre-Fader C/SUB
2
10
23
11
Pre-Fader LS/RS
3
21
9
22
Stereo Input C Direct
4
7
20
8
Post-Fader L/R
5
18
6
19
Post-Fader C/SUB
6
4
17
5
Post-Fader LS/RS
7
15
3
16
Post-Fader Stereo
8
1
14
2
Notes: 1) All signals transformer-coupled digital audio;
balanced AES3 (110 ohms, 5 Vpp) compatible.
2) Connector type on Model 760-01 is 25-pin female
D-subminiature (DB-25F). Installer must provide male
(DB-25M). Connector uses 4-40 threaded inserts for
locking with mating plug.
3) Wiring scheme follows AES59-2012 convention.
Standard TASCAM-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Figure 5. Connections for Digital Monitor Outputs
A wiring assembly prepared for the Model
760-01’s monitor outputs would typically
be identical to that of a TASCAM-type
output assembly. An assembly of this type
would have a 25-pin male D-subminiature
connector (DB-25M) on one end and eight
3-pin male XLR connectors on the other.
Pre-Fader Surround Monitor Output
The pre-fader surround monitor output
channels are intended to connect to metering, measurement, or other signal monitoring equipment that requires uninterrupted,
full-level digital audio signal sources.
For compatibility with AES3 balanced
digital audio signals connect the D-sub’s
+ terminal as signal high and the – terminal as signal low. In most applications a
3-pin male XLR connector will be used.
In this case the + terminal would go to
Stereo Input C Direct Monitor Output
The stereo input C direct monitor output
is intended for use in site-specific applications. It provides an uninterrupted, full-level
digital audio signal source that is post-SRC
and input delay in the signal chain.
Model 760-01/77 User Guide
Studio Technologies, Inc.
Issue 3, April 2015
Page 11
for Surround
Post-Fader Surround Monitor Output
The post-fader surround monitor output
channels are designed for connection to
digital inputs on audio amplifiers associated with monitor loudspeakers. Alternately,
they could be connected to the inputs of
loudspeakers that contain integrated amplifiers with digital audio input capability.
Post-Fader Stereo Monitor Output
The post-fader stereo monitor output
channels are intended to support a stereo
loudspeaker system, either by connecting
to the digital input of an amplifier associated with a set of loudspeakers or directly
to a set of amplified speakers that provide
digital inputs.
Sync Input
The Model 760-01 requires a timing reference (sync) signal so that the digital audio
input and digital monitor output signals
will be handled correctly. A configuration
setting allows the source of sync to be the
L/R input of the currently selected surround or stereo digital audio input. While
this is acceptable, audio artifacts (clicks or
noise) can occur when switching between
inputs. A better method is to connect a
dedicated timing reference signal to the
Model 760-01’s sync input connector. The
connected sync signal must maintain a
stable relationship between itself and the
digital audio input signals. The actual sync
source can be in one of several formats:
word clock, DARS (AES11), bi-level video,
or tri-level video.
An overview of the various compatible
timing reference signals might prove
worthwhile. Word clock is a digital signal
that is locked in phase and frequency to
the sample rate of the associated digital
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audio sources. DARS (digital audio reference source) is a timing signal compliant
with the AES11 standard. It’s sometimes
referred to as “AES3-black.” Technically it
is similar to an AES3 signal but is generated specifically as a timing reference signal.
Bi-level video sync signals were originally
provided to support NTSC and PAL broadcast applications, although they continue
to be used by contemporary equipment.
Tri-level sync signals were primarily associated with facilities that supported highdefinition (HD) video equipment however
the importance of this type of sync seems
to be waning. Both bi-level and tri-level
signals can be found at numerous rate
combinations, configured to allow for compatibility with the various video formats.
With the wide range of allowable sync
sources proper Model 760-01 operation
should be easy to obtain. Extensive testing
has been done using many different sync
source types and rates. Interested users
can refer to Appendix B of this user guide
for details.
An external sync reference source should
be connected to the sync input BNC connector located on the Model 760-01’s back
panel. For flexibility this input can be configured to be high-impedance (“floating”) or
terminated with an impedance of 75 ohms.
A sync source that is dedicated for use by
the Model 760-01’s sync input will typically
have input termination enabled. If the sync
signal connected to the Model 760-01 is
being connected (“multed”) to other inputs
it may be desirable for the termination to
be disabled. A general “rule of thumb” is
that termination should be applied only
at the location of the last physical device
using a sync signal.
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Remote Control Inputs
Support is provided for two remote control
input functions: remote mute all and remote
dim. These functions only impact the postfader surround and stereo monitor outputs.
The Model 760-01’s inputs use logic gates,
“pulled up” to 3.3 Vdc 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 discharge (ESD),
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 configured to change state (“latch”)
in response to a logic pulse.
A 9-pin D-subminiature connector is
used for the remote control inputs. Refer
to Figure 6 or Appendix A for the exact
connection details. Note that pin 4 (remote
common) connects to the Model 760-01’s
internal circuit common connection as well
as to the Model 760-01’s chassis and mains
earth connections. Figure 6 also shows two
spare remote control inputs (pins 8 and 9).
These are provided for future applications
and should remain unconnected.
Signal
Pin
Connecting the Model 760-01
to the Model 77
A 9-pin female D-subminiature connector, labeled To/From Control Consoles, is
provided on the back panel of the Model
760-01 Central Controller. This is used to
interface the unit with Model 77 Control
Consoles. Refer to Figure 7 or Appendix A
for details. A 9-pin female D-sub connector,
labeled To/From Central Controller, is provided on the back panel of each Model 77
Control Console. A cable with 9-pin male
D-sub (DE-9M) connectors on each end
is used to interconnect the Model 760-01
with the Model 77 units. A cable is included
in the shipping carton. The cable implements all nine connector pins in a one-toone 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 supporting all nine pins, only four connections
are required: pin 1 (data +), pin 6 (data –),
pin 4 (DC +), and pin 9 (DC –). The Model
760-01’s connector pin-out scheme was
designed to allow creation of an interconnecting cable which uses commonly
Direction
Signal
Data Shield
1
Shield
Data + (RS-485)
1
To/From Models 77/71
Remote Mute All
5
Input
Data – (RS-485)
6
To/From Models 77/71
Remote Dim
6
Input
Data Shield
2
To/From Models 77/71
Remote Spare 1
8
Input
DC + (12 V)
4
To Models 77/71
Remote Spare 2
9
Input
DC – (12 V Return)
9
To Models 77/71
Remote Common
4
Common
DC Power Shield
5
To/From Models 77/71
Note: Connector type on Model 760-01 is 9-pin female
D-subminiature (DE-9F). Connector uses 4-40
threaded inserts for locking with mating plug.
Figure 6. Connections for Remote Control
Inputs
Model 760-01/77 User Guide
Studio Technologies, Inc.
Pin
Direction
Note: Connector type on Model 760-01 is 9-pin female
D-subminiature (DE-9F). Connector uses 4-40
threaded inserts for locking with mating plug.
Figure 7. Connections between Model 760-01
and Model 77 and Model 71
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for Surround
available 2-pair audio cable. This cable,
consisting of two twisted pairs each with an
individual shield, is typically sleek, flexible,
and available in many colors. One pair and
shield can be used for the data connections
while 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.
A few simple calculations are required to
determine the maximum cable length when
connecting a Model 760-01 to a Model 77.
The differential transmission scheme used
by the system’s RS-485 interface makes
an interconnection in excess of 1000 feet
(>300 meters) easily possible. The limiting
factor is typically the ability of the wiring to
pass the DC power supplied by the Model
760-01 to a Model 77. The Model 760-01
supplies 12 Vdc with a maximum current
of 500 milliamperes (mA).
The Model 77 requires a minimum of
9 Vdc, 100 mA, for correct operation. (The
voltage must be measured directly at the
Model 77’s 9-pin connector.) So the maximum interconnecting cable length is directly
related to the resistive voltage losses associated with the two DC-carrying conductors.
As the Model 760-01 supplies 12 V and
the Model 77 requires 9 V minimum, this
directly leads to a 3 Vdc maximum drop due
to the interconnecting cable. Using Ohm’s
law it’s quite easy to determine whether
the selected cable will support the desired
interconnection length. Calculate the voltage drop by multiplying the total resistance
(in ohms) of the proposed cable by 0.1 (the
Model 77’s required current in amperes).
Remember to include the resistance in
both the DC + and DC – wires when
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calculating the voltage drop. If it’s greater
than 3 V your cable is too long or the wire
gauge is too small.
Additional Control Consoles
Some installations may benefit from the
Model 760-01’s ability to be controlled by
additional control consoles. At least one
Model 77 Control Console must be connected to the Model 760-01 Central Controller. After this requirement has been met
up to three additional Model 77 or Model
71 Control Consoles can also be connected to and powered by the Model 760-01.
When connecting multiple control consoles
to a Model 760-01 all nine pins of each
interconnecting cable can be connected in
parallel (“multed”). Using this arrangement
the data and 12 Vdc power signals between all the units will be multed. A custom
cable implementation requires just four
pins to be connected: pin 1 (data +), pin 6
(data –), pin 4 (DC +), and pin 9 (DC –).
To make installation simple, a “bus” cable
assembly can be created using a short
length of ribbon cable with one male and
multiple 9-pin female D-subminiature
insulation-displacement connectors
attached. Then standard 9-pin cables
can link the control consoles with the
connectors on the bus cable.
Refer to the previous paragraphs of this
user guide where the issues involving
Model 760-01 to Model 77 cable length
are discussed. Note the required current
for a Model 77 is 100 mA while a Model
71 requires only 35 mA. It’s important to
review this information prior to creating
the interconnection scheme to be used for
installing multiple Model 77 units.
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AC Mains Power
The Model 760-01 operates directly from
AC mains power of 100 to 240 V, 50/60 Hz.
Being a “universal input” device, there are
no switches to set or jumpers to install to
match a location’s mains voltage. The unit
uses a 3-pin IEC 320 C14-type inlet connector to mate with a detachable mains
cord. All units are supplied with a mains
cord that has a North-American-standard
plug (NEMA 5-15L) on one end and an
IEC 320 C13 socket on the other. Units
bound for other destinations require that
the appropriate cord be used. The wire colors in the mains cord must conform to the
internationally recognized color code and
should be terminated accordingly:
Connection
Neutral (N)
Line (L)
Protective Earth (E)
Wire Color
Light Blue
Brown
Green/Yellow
Safety Warning: The Model 760-01
does not contain an AC mains disconnect switch; the AC mains cord
plug serves as the disconnection
device. Safety considerations require
that the plug and associated outlet
be easily accessible to allow rapid
disconnection of AC mains power
should it prove necessary.
As soon as mains power is applied the
Model 760-01 will perform a power-up
sequence. The two LEDs on the right side
of the front panel will individually light in a
rapid right-to-left test sequence. Then the
LEDs will flash in cadence while the firmware loads into the Model 760-01’s main
logic device. After just a few seconds initial
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system operation will commence and the
two LEDs will perform their intended functions. Once operating data is being interchanged with the one or more connected
Model 77 or Model 71 Control Consoles
the control console status LED will also
light. The sync status LED will light if a
valid sync source has been recognized.
The sync status LED will flash if a valid
sync source is not recognized.
Also upon application of mains power, all
connected Model 77 units will go through
a power-up sequence, lighting each of its
LEDs in succession. Using its 4-digit display, each Model 77 will then momentarily
display its address, its software version,
and the main and logic device software
versions of the associated Model 760-01.
All connected Model 71 units will also go
through a power-up sequence after mains
power is applied to the Model 760-01.
Each of the Model 71’s three LEDs will
light momentarily. After these LEDs have
been lit, the device address will be shown
briefly using the dim and reference level
LEDs, as shown in Figure 8 in the Configuration section. When this is complete the
Model 71 will begin normal operation and
its status LED will light if communication is
established with the Model 760-01. If the
Model 71’s status LED does not light check
to see if there is a device address conflict
among all connected control consoles and
that all cables are connected properly.
Should an error be detected during the
start-up process the two LEDs on the
Model 760-01’s front panel will remain
flashing in cadence. On the Model 77 units
a diagnostic code may be displayed. Refer
to the Technical Notes section of this user
guide for details.
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Only after the Model 760-01 and all connected Model 77 and Model 71 units have
correctly powered up will full system operation begin.
Configuration
After the physical installation has been
completed it’s important that the system’s
configuration options be carefully reviewed.
In most cases one or more of the operating
parameters will need to be revised to meet
the needs of the specific installation. Many
of the configuration parameters will impact
the signal flow in to and out of the Model
760-01 Central Controller. Other parameters
affect how the one or more Model 77 Control Consoles will display status conditions
and respond to user commands. Most of the
configuration choices will be made using a
Model 77 Control Console. However, two
configuration choices are available for each
of the connected Model 71 Control Consoles.
Configurable Parameters
Many StudioComm functions can be configured to meet the exact needs of an installation. A Model 77 Control Console is used
to display and select the desired system
configuration. Here’s an overview of what
can be configured:
• Model 77 Device Address (must be
unique for each unit!)
• Stereo Input C Sample Rate Converter
• Post-Fader Stereo Monitor Output
• Bass Management
• Mute/Solo Bass Management Mode
• Sync Source
• Sync Input Termination
• Audio-Synced-to-Video Sample Rate
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• Reference Level
• Overall Display Mode
• Reference Level in dB SPL
• Auto Reference Level Off
• Dim Level
• Remote Inputs
• Surround to Stereo Downmix Levels
• Pre-Fader Surround Monitor Output
Mode
• Channel Pop Solo Mode Offset Levels
• Input Delay A and B
• Post-Fader Monitor Output Channel Level
Offsets
The configuration diagrams, located later
in this section, give details on setting each
parameter. An overview of each configurable parameter is provided in the following
paragraphs.
Entering and Exiting the
Configuration Mode
A small button is located on the back of
each Model 77 Control Console, adjacent
to its 9-pin female D-sub connector. On any
connected Model 77 pressing and holding this button for two seconds places both
this specific unit and the Model 760-01
into their configuration modes. Other connected Model 77 and Model 71 units will
enter a standby mode. When the Model
760-01 enters its configuration mode it will
immediately mute the monitor outputs as a
speaker protection measure. When a Model
77 enters the configuration mode its array
of buttons and LEDs no longer perform their
normal functions, instead they are used to
display the operating parameters and reflect
configuration changes as they are made.
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for Surround
As a user aid, a Model 77 that has entered
the configuration mode will have its mute
and solo LEDs (associated with the channel mute/solo section) light in an alternating
manner. Other connected Model 77 units
will indicate that they have entered the
standby mode by simultaneously flashing
their mute and solo LEDs.
To leave the configuration mode and return
the system to normal operation requires
one last action to be made on the Model 77
unit that’s in its configuration mode; press
and hold its configuration button for two
seconds. Note that configuration changes
are stored in nonvolatile memory only after
the configuration mode has been exited.
Our apologies to those of you who find the
configuration button a pain to use, but it’s
supposed to be that way! Seriously, the top
of the button is slightly recessed from the
back panel, making it harder to accidentally
activate. We didn’t want normal operation to
cease because someone pushed a Model
77 into a “rats nest” of schedules, memos
from management, and empty coffee cups!
But a firm press with the fleshy part of an
index finger should do the trick.
There is no problem frequently “tweaking” the system’s operating parameters to
achieve the desired performance. The configuration data is stored in nonvolatile memory, which is rated for thousands of read
and write cycles and a retention time in tens
of years. Note that memory integrated circuits are located in the Model 760-01 Central Controller as well as the Model 77 and
Model 71 Control Consoles. The individual
device address is stored in each Model 77.
The device address and button configuration parameters are stored in the Model
71. All other configuration parameters are
stored in the Model 760-01.
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Model 77 Device Address
A unique device address must be assigned
to each Model 77 that is connected to a
Model 760-01. The choices are A1, A2, A3,
or A4, with the default address being A1. As
most installations will find only one Model
77 utilized, its default setting is appropriate.
For installations that use a second, third, or
fourth Model 77 each unit must be configured with a unique device address. Problems
will occur if more than one unit has the same
address! It’s important to highlight the fact
that the device address is the only setting
that must be done on each individual Model
77 unit. All other settings can be made on
any one of the connected Model 77 units.
Be sure that any selected address does
not conflict with addresses to be assigned
to Model 71 units.
Stereo Input C Sample Rate
Converter
Circuitry associated with stereo input C can
provide sample rate conversion (SRC) for
digital audio signals connected to that input.
The acceptable input range for sample rate
conversion is very wide, but is dependent
upon the output sample rate. With an output
sample rate of 48 kHz any signal with
a sample rate over a range of 8 to 216 kHz
can be properly monitored by the system.
This capability can be especially useful with
signals that are not synchronized with respect to the others connected to the Model
760-01, even if the sample rate is identical.
The only compromise is that the SRC process adds a fixed input-to-output (group)
delay of approximately 1 millisecond, a value
that shouldn’t impact most installations. As
such, it’s recommended that the sample rate
converter remain enabled. However there
might be special cases where this resource
isn’t desired and it can be disabled.
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Post-Fader Stereo Monitor
Output
In addition to the post-fader surround monitor output, a separate post-fader stereo
monitor output is also provided. By default
the stereo output can be enabled by a user.
In applications where stereo monitor loudspeakers are not connected to the postfader stereo monitor output, the output can
be disabled. This can minimize confusion,
preventing a user from attempting to select
the post-fader stereo monitor output.
Bass Management
The Model 760-01 incorporates flexible
and sonically excellent bass management capabilities. It is, however, limited to
functioning only at sample rates of 44.1,
48, 88.2, and 96 kHz. Five configuration
parameters are used to enable or disable
bass management as well as to select the
characteristics of the associated audio filters. While the settings are simple to make,
great care must be taken in first reviewing
the entire monitor system. Only after a full
understanding of the performance of the
associated surround and, if present, stereo
loudspeaker systems are determined can a
plan for bass management be established.
Bass management can be enabled so that
the function is active when the surround
post-fader monitor outputs are enabled. It
can also be independently enabled so that
it can be active when the stereo post-fader
monitor outputs are enabled. By default
bass management for both outputs is disabled. The crossover point of the bass
management filters can be selected from
among four choices: 40, 50, 60, or 80 Hz.
The slope of the low-pass and high-pass filters associated with bass management can
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be independently selected. The choices
are 12 dB-per-octave or 24 dB-peroctave with the latter being the default.
Mute/Solo Bass Management
Mode
The Model 760-01’s mute/solo function can
be configured for how it performs in applications where bass management has been
enabled. This is a somewhat-esoteric topic
but can be important in certain situations.
The default setting for the mute/solo bass
management mode is for pre-bass management. This means that if a channel has
been selected for, as an example, soloing
then the bass management filters will send
any applicable low-frequency content to
the post-fader subwoofer output. So in this
case the solo function is really an “input
channel” solo since the actual acoustical
energy associated with that channel will be
reproduced by both the main channel and
the subwoofer loudspeakers. So while one
is “soloing” a channel (or set of channels)
two or more loudspeakers may be reproducing the signals.
The mute/solos bass management mode
can also be set for post-bass management. When this mode is enabled a channel selected for soloing will cause only
its associated post-fader monitor output
channel to remain active. So if, for example, one of the main surround input channels (one of the “5.” channels) is selected
for soloing then all post-fader output channels except that one will mute. The bass
management filters will remain enabled,
thus sending only the high-passed audio
energy from the soloed input channel to
the soloed output channel. Only if the LFE
channel has been selected for soloing will
the subwoofer output remain active. Typically the only reason why the post-bass
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for Surround
management mode would be selected is
when troubleshooting issues with the loudspeaker system.
Sync Source
The Model 760-01 requires that the designated external timing reference (sync) be
defined. Three of the choices—word clock,
DARS, and video—are associated with a
signal that is connected to the sync input
BNC connector. The fourth choice allows
the L/R input of the currently selected surround or stereo digital audio input to serve
as the system’s sync source.
Sync Input Termination
The sync input circuitry can be configured
to terminate the signal connected to the
back-panel sync input BNC connector.
When termination is selected a 75 ohm
load is applied to the signal. When the
sync input is not terminated the input impedance is very high, essentially applying
no load to the source. If the sync source is
connected only to the Model 760-01 then
enabling termination is typically appropriate. However, if the sync source is being
“shared” by multiple inputs then care must
be taken so that the signal is only terminated by one device.
Audio-Synced-to-Video
Sample Rate
If a video sync signal is being used as the
Model 760-01’s timing reference the sample rate of the connected digital audio signals must be specified. In most cases the
default value of 48 kHz will be appropriate,
but rates from 32 to 192 kHz are available.
Model 760-01/77 User Guide
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Reference Level
For audio-with-picture applications it’s
often beneficial for monitoring to be done
in reference to a known loudspeaker
level. This is often referred to as “mixing
to 85 dB” on the monitors. The StudioComm for Surround system allows a
precise post-fader surround monitor output
level to be stored, and then enabled by
pressing the Model 77 button labeled
Reference Level. Setting the reference
level is very simple but care is required.
Typically this will be done in reference to
the surround monitor output, rather than
the stereo monitor output:
1. Set up a precision sound pressure
level (SPL) measuring device at the
desired listening location.
2. Place the StudioComm system in the
normal operating mode, not the configuration mode. Be certain that the dim,
mute all, reference level, and downmix
functions are not active. The remote
mute all and remote dim functions
must also not be active.
3. Use the Model 77 Control Console to
select the input source that contains
the desired reference signal source,
e.g., pink noise.
4. Observing the SPL meter, adjust the
Model 77’s rotary level control until the
desired loudspeaker system reference
level has been reached.
5. Being careful not to disturb the position
of the rotary level control, enter the
configuration mode by pressing and
holding the configuration button located on the Model 77’s back panel.
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6. Once the configuration mode has been
entered, all the monitor outputs will mute.
Press and hold the reference level button; its associated LED will begin to flash.
After five seconds the LED will light
steadily to indicate that a “snapshot” of
the new reference level has been taken.
The Model 77’s numeric display will then
show the value of the new reference
level. The value shown will always be a
negative number as it’s always a value
less than the maximum output level.
The reference level button can now be
released.
7. To complete the process the configuration mode must be exited. This is performed by again pressing and holding
the configuration button for two seconds.
The new reference level is now stored in
the Model 760-01’s nonvolatile memory.
Only by repeating the entire procedure
can the value be changed.
Once the configuration mode has been exited, the monitor outputs will again become
active. Confirm that the correct level has
been stored by pressing the reference level
button. The SPL meter should display the
desired level. If not, repeat the calibration
procedure to achieve the desired goal.
You might wonder why you have to press
and hold the reference level button for five
seconds before the selected value is recognized. This is provided specifically so that
unauthorized users won’t accidentally
change the reference level while they experiment with the configuration mode. Only if
you know the “secret” will you be able to
store a new value.
Overall Display Mode
The Model 77’s 4-digit numeric display
can be configured to display the post-fader
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monitor output levels in either an attenuation mode or an SPL mode. In the attenuation mode the output level is shown as
a reduction in level, in dB, relative to the
maximum output level. When the rotary
control is used to set the output level to
its maximum the display will show 0.0. As
the rotary control is turned in the counterclockwise direction the display will show
negative values, reaching –70.0 before the
full mute function automatically mutes the
monitor outputs.
In the SPL mode the display can be configured to allow the output level to be
presented to users in terms of the actual
sound pressure level (SPL). It is used in
conjunction with the reference level in dB
SPL configuration and the stored reference
level. The SPL mode allows a user to see
a visual representation of the SPL level
that is present in the listening environment.
While it takes a little more care to correctly
implement the SPL display mode, it can
offer an enhanced experience for StudioComm users.
Reference Level in dB SPL
The reference level in dB SPL configuration allows a specific SPL value to be
associated with the stored reference level
value. In this way whenever the post-fader
monitor outputs are at the reference level,
either through activating the reference level
function or manually adjusting the rotary
level control, the Model 77’s display will
show the configured SPL level. Whenever
the monitor output is not at the reference
value the display will show the current
value, in dB, relative to the reference level.
The reference level in dB SPL can be configured over a range of 70.0 to 100.0 dB in
1.0-dB steps. In many applications selecting a value of 85 would be appropriate,
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for Surround
reflecting the widely used audio-for-picture
85 dB monitoring reference level. (Typically
this 85 dB is really 85 dBC, indicating that
a C-weighting filter has been applied to the
measurement.) Other common reference
SPL values, such as 82 dB and 87 dB, are
well within the allowable range.
Auto Reference Level Off
When auto reference level off is enabled,
the function automatically turns the reference level function off if a change is made
to the rotary level control while the reference level function is active.
Dim Level
The dim function is used to reduce the
post-fader surround and stereo monitor output levels by a preset amount. The
reduction is in dB relative to the post-fader
surround and stereo monitor outputs’
current level. There are four dim level
values available: –10.0, –15.0, –20.0,
and –25.0 dB.
Remote Mute All
Two configuration choices are associated
with the remote mute all function: disabled
and enabled. To utilize the remote mute all
function simply requires you to select the
enabled setting.
Remote Dim
Two configuration choices are associated
with the remote dim function: disabled and
enabled. To utilize the remote dim function
simply configure it for enabled.
Input Delay
A time delay can be added to the input
signals, allowing compensation for delays
that may be present on associated video
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signals. The time delay applies to all input
signals and cannot be applied selectively.
A configured delay time is referenced to a
sample rate of 48 kHz. In the case of input
signals with a sample rate of 48 kHz the
delay range is 0 to 340 milliseconds in
1-millisecond steps. For other sample rates
the time must be linearly scaled. For example, for a sample rate of 96 kHz the actual
time range is 0 to 170 milliseconds. In this
case selecting a delay of 120 on the Model
77 will result in an actual time delay of 60
milliseconds.
For operating flexibility two different input
delay values can be selected and stored
during the configuration process. These
can then be enabled as required by the
user during normal system operation.
The default value for both Delay A and
Delay B is 0 milliseconds. Typical applications would require only one input delay
to be configured. But in other cases two
different, both non-zero, input delay values
will be selected. This could be appropriate
in applications where multiple video display systems are being used in the same
control room or monitoring facility. Each
video display may exhibit its own processing latency and audio would need to be
“lined up” accordingly. During normal
StudioComm operation a user can select
the appropriate input delay for the display
system currently being utilized.
Surround to Stereo Downmix
Levels
The surround to stereo downmix function
is a useful tool for checking the compatibility of surround (5.1) input signals with
stereo and monaural playback environments. The exact technical formula for how
the Model 760-01 handles the surround to
stereo downmix function can be selected
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by way of four configurable parameters.
The default settings create a good generalpurpose function that’s effectively used by
numerous users of Studio Technologies’
StudioComm for Surround products. But
there are application-specific situations
where modifying one or more of the parameters will be appropriate. This can be in
response to a personal choice in monitoring methods or, more frequently, to meet
the requirements of international broadcast
standards.
When the surround to stereo downmix
function is active the path from the left (L)
input channel to the left post-fader output
channel and the right (R) input channel to
the right post-fader output channel is maintained. A configuration choice allows the
level of the L and R inputs routed to the L
and R outputs to be selected. By default,
when the surround to stereo downmix
function is active the level of the L and R
inputs remain at unity, with no gain or loss
applied. An alternate setting allows the
level of L and R input channels to be reduced (attenuated) by 3 dB. (The available
changes in signal level can also be notated
as 0 dB or –3 dB.)
When the surround to stereo downmix
function is active the left surround (LS) input is routed to the left (L) post-fader monitor outputs; the right surround (RS) input
is routed to the right (R) post-fader monitor outputs. By default the level of the LS
and RS signals routed to L and R will be
reduced (attenuated) by 3 dB. An alternate
setting allows the levels to be reduced by
6 dB. (These settings can also be notated
as –3 dB and –6 dB.)
When the surround to stereo downmix
function is active the center (C) input is
routed to both the left (L) and right (R)
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post-fader monitor outputs. By default the
level of the C signal routed to L and R will
be reduced (attenuated) by 6 dB. An alternate setting allows the attenuation level to
be 3 dB. (These levels can also be notated
as –3 dB and –6 dB.)
By default, when the surround to stereo
downmix function is active the LFE channel
associated with a surround input is fully attenuated (muted). This removes LFE content from the “downmixed” signal. In most
applications this is appropriate. However,
for special situations a configuration mode
allows the LFE channel to be reduced by
6 dB and routed to both the left (L) and
right (R) post-fader monitor outputs.
A last word on configuring the surround to
stereo downmix function: no matter what
choices are made when the function is active the center (C), left surround (LS), right
surround (RS), and subwoofer (SUB) postfader monitor outputs will fully mute.
Pre-Fader Surround Monitor
Output Mode
The pre-fader surround monitor output
can be configured as to its place in the
Model 760-01’s signal flow. The choices are
pre- or post-downmix. In the pre-downmix
mode the monitor output channels will not
be impacted by the state of the downmix
functions. This setting would be appropriate
if the pre-fader surround monitor outputs
were being routed to a storage system,
routed to another facility, etc. In this case
the action of a user enabling or disabling
the downmix functions won’t impact the
pre-fader surround monitor output signals.
If the post-downmix mode is selected the
pre-fader surround monitor outputs will
reflect the actions of the downmix functions.
This choice would be correct if, for example,
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for Surround
level meters were connected to the prefader surround monitor outputs. In this scenario a user would want to visually observe
the actions that the downmix functions
impart on the signals.
Channel Pop Solo Mode Offset
Levels
Two parameters can be configured that
determine how the channel pop solo function impacts audio levels. The up offset level
sets the amount of increase (gain) that a
channel will experience when it is soloed
in the channel pop solo mode. The down
offset level sets the amount of decrease
(attenuation) that the non-soloed channels
will experience when a channel is active
in the channel pop solo mode. Refer to
Figure 10 for details.
Post-Fader Monitor Output
Level Offsets
To provide assistance during room calibration, the relative output levels of the postfader surround and stereo monitor output
channels can be adjusted over a limited
range. The eight channels can be adjusted
in 0.5-dB steps over a ±12-dB range. During configuration the displayed value represents the dB level difference as compared
to the nominal output level. In most cases
one surround and one stereo channel
should serve as the overall reference level
and not be changed. This is typically the
center channel for surround and the left
channel for stereo.
This feature is provided primarily for use
when the post-fader monitor output channels are connected to loudspeaker systems
that don’t offer a means of “trimming” the
input sensitivity of individual channels.
Without this capability, minor adjustments
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to the output level of specific loudspeakers
to account for room acoustics wouldn’t
be possible.
It’s also possible to use the StudioComm’s
output level offset capability to adjust the
overall post-fader monitor output levels to
allow matching to the input sensitivity of
loudspeaker systems. In this case all the
channels (six for surround, two for stereo)
would be configured to have the same
output level offset setting. For example, the
six surround channels could all be configured to have a –3.5 dB output level offset.
However, great care must be taken when
configuring a system in this manner. The
dynamic range or noise floor of the audio
signals will be impacted and extreme settings could lead to poor monitor system
performance.
Restore Factory Defaults
The restore factory defaults function is provided primarily for factory use. In this way
a system can be shipped with the default
settings selected. While you are welcome
to use this function, be careful so that your
configuration efforts aren’t wasted. Specifically, be aware that the reference level
is reset to minimum level. All the other
parameters are fairly easy to set up, but
resetting the reference level would require
getting out an SPL meter and a calibrated
signal source. This is a hassle you may not
need!
Model 71 Control Console
Configuration
Two configuration choices are available on
each Model 71. One is its device address,
the other is the button disable mode. A
small button is located on the back of each
Model 71 Control Console, adjacent to the
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9-pin female D-sub connector. Pressing
and holding this button for two seconds
places this specific unit in its configuration mode; normal operation of the Model
760-01 and other connected Model 71
and Model 77 units will continue. When a
Model 71 enters its configuration mode
its three LEDs will no longer perform their
usual functions. Instead the status LED will
blink to indicate that configuration mode is
active. Refer to Figure 8 for details.
connected Model 71 or Model 77 Control
Console. The choices are A1, A2, A3, and
A4. All Model 71 units have a default device address of A4; Model 77’s units have a
default device address of A1. This ensures
that, in most cases, no change will have to
be made. Refer to Figure 9 for details.
Address
Dim LED
Reference Level LED
A1
OFF
OFF
A2
OFF
ON
A3
ON
OFF
A4
ON
ON
Figure 9. Model 71 Device Address Chart
Button Disable
To disable the Model 71’s buttons, simultaneously press and hold both the dim and
reference buttons for two seconds. When
the disable request has been recognized
the LEDs above both buttons will flash
rapidly. Release the buttons and they will
no longer enable or disable their normal
functions. To return the buttons to normal
operation simultaneously press and hold
both buttons for two seconds at which time
the two LEDs will flash rapidly.
Figure 8. Model 71 Control Console Front and
Back Panels
Device Address
The dim and reference level LEDs will
display the Model 71’s current device
address. The rotary level control is used
to select the desired device address; the
LEDs will respond accordingly. The device
address must be selected so as not to conflict with the device address of any other
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To leave the configuration mode and return
a Model 71 to normal operation requires
one last action: again press and hold its
configuration button for two seconds. The
selected configuration parameters will be
stored in a nonvolatile memory device that
is located inside this specific Model 71.
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Entering and Exiting Configuration Mode
and hold the configuration
 Press
button for 2 seconds to enter or
exit the configuration mode.
These LEDs will light alternately
when configuration mode is active.
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Issue 3, April 2015
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for Surround
Configuration—Model 77 Device Address, Stereo Input C
Sample Rate Converter, and Post-Fader Stereo Monitor Output

Press and hold the Mute/Solo
button to display and configure the
Model 77’s device address, stereo
input C sample rate converter, and
post-fader stereo monitor output.
This LED displays the configuration of the
stereo input C sample rate converter
(SRC). LED not lit means SRC is disabled;
LED lit means SRC enabled. Use the button
to change the configuration.
These LEDs display the status of the post-fader stereo
monitor output function. When LED Surround is lit the
function cannot be enabled. When LED Stereo is lit the
function can be enabled. Use the button to change the
configuration.
Use the Level control to change this
specific Model 77’s device address.
Address can be either A1, A2, A3, or A4.
See Note below.
Default:
Device address A1.
Stereo input C sample rate converter enabled.
Post-fader stereo monitor output can be enabled.
Note:
The Model 77’s device address is the only parameter stored in the Model 77. All other parameters are stored
in the Model 760-01.
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Bass Management and Mute/Solo Bass
Management Mode
This LED displays the configuration of
the surround output bass management.
LED lit means surround output bass
management enabled; LED not lit means
surround output bass management
disabled. Use the button to change
the configuration. See Note below.
Use these
buttons to select
bass management low-pass
filter slope.
LED Surround A
lit means
24 dB-per-octave;
LED Surround B
lit means
12 dB-per-octave.
This LED displays the configuration of
the stereo output bass management.
LED lit means stereo output bass
management enabled; LED not lit
means stereo output bass management
disabled. Use the button to change
the configuration. See Note below.
This LED displays
the configuration
of the mute/solo
bass management mode. LED
lit means mute/
solo functions
occur post-bass
management;
LED not lit means
mute/solo functions occur prebass management.
Use the button
to change the
configuration.
Use these
buttons to select
bass management high-pass
filter slope.
LED Stereo A
lit means
24 dB-per-octave;
LED Stereo B
lit means
12 dB-per-octave.

Press and hold the Stereo C button
to display and configure the bass
management and mute/solo bass
management mode settings.
Use the Level control to select the
bass management crossover
frequency. Choices are 40, 50,
60, or 80 Hz.
Default:
Surround output bass management disabled.
Stereo output bass management disabled.
Bass management low-pass filter slope 24 dB-per-octave.
Bass management high-pass filter slope 24 dB-per-octave.
Bass management crossover frequency 80 Hz.
Mute/solo pre-bass management mode.
Note:
Bass management capability only available at sample rates of 44.1, 48, 88.2, and 96 kHz.
Model 760-01/77 User Guide
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Issue 3, April 2015
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for Surround
Configuration—Sync Source, Sync Input Termination, and
Audio-Synced-to-Video Sample Rate
This LED displays the configuration of the sync input termination.
LED not lit means sync input is not terminated; LED lit means terminated with 75 ohms. Use the button to change the configuration.

Use these buttons
to select the sync
source.
LED Surround B
lit means sync
input, video;
LED Stereo A lit
means sync input,
DARS;
LED Stereo B lit
means sync input,
word clock;
LED Stereo C
lit means L/R of
currently selected
input.
Press and hold
the Stereo to
Mono button to display
and select the
sync source,
sync input
termination, and
audio-syncedto-video-sample
rate.
Use the level control to adjust the audiosynced-to-video sample rate. Available
sample rates are 32, 44.1, 48, 88.2, 96,
176.4, and 192 kHz.
Default:
Sync source is L/R of currently selected input.
Sync input terminated.
Audio-synced-to-video sample rate 48 kHz.
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Reference Level
and hold the Reference Level button for 5 seconds to take a “snapshot”
 Press
of the level control’s setting at the time configuration mode was entered. The
Reference Level LED will flash when the button is initially pressed and then
light steadily when the “snapshot” has been taken. See Note below.
Default:
Reference level set for –60.0 dB post-fader monitor output level.
Note:
The 5-second button-press delay is a safety feature ensuring that the reference level will not be accidently
changed. To permanently store the new value, you must still exit the configuration mode.
Model 760-01/77 User Guide
Studio Technologies, Inc.
Issue 3, April 2015
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for Surround
Configuration—Overall Display Mode, Reference Level
in dB SPL, and Auto Reference Level Off
When the Mute All button is pressed, use the Channel Mute/Solo
L and R buttons to select the overall display mode. LED L lit
means attenuation mode is selected; LED R lit means SPL mode
is selected. Use the buttons to change the configuration.
When the Mute
All button is
pressed, use the
Reference Level
button to enable
or disable auto
reference level
off. When the
Reference Level
LED is lit auto
reference level
off is enabled.
Press and hold the Mute All button to
 display
and set the overall display mode,
the reference level in dB SPL, and auto
reference level off.
Default:
When the Mute All button is pressed,
use the Level control to adjust the
reference level in dB SPL.
Attenuation display mode selected.
85.0 dB SPL reference level.
Auto ref level off disabled.
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Dim Level, Remote Mute All, and Remote Dim
This LED displays the configuration of
remote mute all. LED not lit means
remote mute all is disabled; LED lit
means enabled. Use the button to
change the configuration.
This LED displays the configuration
of remote dim. LED not lit means
remote dim is disabled; LED lit
means enabled. Use the button to
change the configuration.
Use these buttons
to select dim level.
LED Surround B lit
means –10 dB;
LED Stereo A lit
means –15 dB;
LED Stereo B lit
means –20 dB;
LED Stereo C lit
means –25 dB.
and hold the Dim button to
 Press
display and select the dim level,
remote mute all, and remote dim.
Default:
–20 dB dim level.
Remote mute all enabled.
Remote dim enabled.
Model 760-01/77 User Guide
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Issue 3, April 2015
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for Surround
Configuration—Surround to Stereo Downmix Levels and
Pre-Fader Surround Monitor Output Mode
These LEDs display the configuration of
the pre-fader surround monitor output
mode. LED L lit means output channels
are pre-downmix; LED R lit means output
channels are post-downmix. Use the
buttons to change the configuration.
Use this button to select the
level change for the LFE
channel when the surround
to stereo downmix function
is active. LED not lit means
full attenuation; LED lit means
–6 dB.
Use these buttons to select
the level change for the
center channel when the
surround to stereo downmix function is active.
LED LS lit means –3 dB;
LED RS lit means –6 dB.
Use these buttons
to select the level
change for the left
and right channels
when the surround
to stereo downmix
function is active.
LED Surround A
lit means 0 dB;
LED Surround B
lit means –3 dB.

Press and hold
the Surround to
Stereo button
to display and
confirm the
surround to
stereo downmix
levels and prefader surround
monitor output
mode.
Use these buttons
to select the level
change for the left
surround and right
surround channels
when the surround
to stereo downmix
function is active.
LED Stereo A
lit means –3 dB;
LED Stereo B
lit means –6 dB.
Default:
L and R channel level change 0 dB when surround to stereo downmix function active.
LS and RS channel level change –3 dB when surround to stereo downmix function active.
C channel level change –6 dB when surround to stereo downmix function active.
LFE level change full attenuation when surround to stereo downmix function active.
Pre-fader surround monitor outputs pre-downmix.
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Channel Pop Solo Mode Offset Levels

Press and hold
the Surround A
button to display
and select the
channel pop solo
up offset level.

Press and hold
the Surround B
button to display
and select the
channel pop solo
down offset level.
When the Surround A button is pressed, use the level
control to adjust the channel pop solo up offset level.
The range is 0.0 to 12.0 in 0.5-dB steps.
When the Surround B button is pressed, use the level
control to adjust the channel pop solo down offset level.
The range is –0.0 to –12.0 in 0.5-dB steps and full mute.
Full mute is selected by adjusting the level control past
–12.0, at which point the display will show – – – –.
Default:
6.0 dB channel pop solo up offset level.
–6.0 dB channel pop solo down offset level.
Model 760-01/77 User Guide
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Issue 3, April 2015
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for Surround
Configuration—Input Delay Settings

Press and hold the
Stereo A button to
display and select
input delay A.

Press and hold the
Stereo B button to
display and select
input delay B.
Use the level control to adjust the input delay.
Range is from 0 to 340. The display shows
delay in milliseconds at 48 kHz sampling
rate. The value is scaled up or down for other
sample rates.
Default:
Input delay 0 ms for both A and B.
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Post-Fader Monitor Output Level Offsets

Press and hold
the L button
to configure
the surround L
level offset.

Press and hold
the R button
to configure
the surround R
level offset.

Press and hold
the C button to
configure the
surround C
level offset.

Press and hold
the LFE button
to configure the
surround SUB
level offset.

Press and hold
the LS button to
configure the
surround LS
level offset.

Press and hold
the RS button
to configure the
surround RS
level offset.

Press and hold both
the L and Surround/
Stereo buttons to
configure the stereo
L level offset.
Press and hold
both the R and
Surround/Stereo
buttons to configure
the stereo R level
offset.
Use the level control to adjust the post-fader monitor output
level offsets. The range is –12.0 to 12.0 in 0.5-dB steps.
Default:
0.0 dB post-fader surround monitor output level offsets.
0.0 dB post-fader stereo monitor output level offsets.
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for Surround
Configuration—Restore Factory Defaults
and hold both the Surround/Stereo and Dim buttons for 5 seconds
 Press
to restore Model 77 factory defaults. Once defaults have been restored,
the associated LEDs will light. After the buttons are released, configuration
mode will be exited and normal operation will resume. See Note below.
Factory Defaults:
Device address A1.
Stereo input C sample rate converter enabled.
Post-fader stereo monitor outputs can be enabled.
Surround output bass management disabled.
Stereo output bass management disabled.
Bass management low-pass filter slope 24 dB-per-octave.
Bass management high-pass filter slope 24 dB-per-octave.
Bass management crossover frequency 80 Hz.
Mute/solo pre-bass management mode.
Sync source is L/R of currently selected input.
Sync input terminated.
Audio-synced-to-video sample rate 48 kHz.
Reference level set for –60.0 dB post-fader monitor
output level.
Attenuation display mode selected.
85.0 dB SPL reference level.
Auto reference level off disabled.
–20 dB dim level.
Remote mute all enabled.
Remote dim enabled.
L and R channel level change 0 dB when surround to
stereo downmix function active.
LS and RS channel level change –3 dB when surround to
stereo downmix function active.
C channel level change –6 dB when surround to stereo
downmix function active.
LFE level change full attenuation when surround to stereo
downmix function active.
Pre-fader surround monitor outputs pre-downmix.
6.0 dB channel pop solo up offset level.
–6.0 dB channel pop solo down offset level.
Input delay 0 ms for both A and B.
0.0 dB post-fader surround monitor output level offsets.
0.0 dB post-fader stereo monitor output level offsets.
Warning: Each Model 77 unit must have a unique address. Restoring factory defaults will reset only this specific
Model 77 to device address A1. If another connected unit is already configured for address A1, normal system
operation will stop.
Note:
The 5-second button-press delay is a safety feature ensuring that the factory defaults will not be accidently
restored.
Issue 3, April 2015
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Operation
Now that you’ve installed and configured the
system, you’re ready to go. You should find
operation very easy. However, taking time
to study this section of the user guide may
prove valuable.
Upon AC mains power up the system will
return to the last operating condition, including the selected source, downmix modes,
etc. As a precaution, however, the post-fader
surround and stereo monitor output levels
will always return to their minimum value.
The rotary level control or the reference
level button must then be used to return the
system to the desired monitor output level.
Model 760-01 Central
Controller
The Model 760-01’s front panel contains two
LEDs. The control console status LED will
light whenever the Model 760-01 is communicating with the one or more connected
Model 77 or Model 71 units. A flashing
control console status LED will indicate that
the DC power output supporting the control
consoles is in a short circuit or over-current condition. The control console status
LED will not light when a Model 77 is in the
configuration mode or when the Model 77 is
going through its power-up sequence.
The sync status LED will light whenever a
valid timing reference signal is being received by the Model 760-01. A flashing sync
status LED indicates that a valid sync signal
is not being received.
Control Consoles
StudioComm for Surround operation is
controlled using the up to four Model 77 or
Model 71 Control Consoles that have been
connected. Two system functions can also
Model 760-01/77 User Guide
Studio Technologies, Inc.
be controlled by means of the remote control inputs.
Model 77 Control Console
To make things easy to describe, the
Model 77’s operator functions are divided
into six main groups: input source selection,
downmix, monitor output general functions,
channel mute/solo, display and display
mode, and remote control inputs.
Any change made to any one Model 77
unit will be reflected in the LEDs and displays on all the connected units. Note that
all control consoles function simultaneously—there is no priority of one unit over
the others.
Input Source Selection
To select an input source press one of the
five input source buttons. The corresponding LED will light to indicate that the input
has been selected. Typically, only one
source will be selected for monitoring at
any one time. However, input stereo C can
be selected by itself, or mixed (summed)
with one of the other four inputs. To accomplish this is easy: simply press and hold
input stereo C then press the button associated with the other desired input source.
The two corresponding LEDs will light.
Alternately, press and hold the first desired
input (other than input stereo C) and then
press the input stereo C button.
It’s possible (although unlikely) that selecting an input will result in the mute all
function being enabled and an Err3 message being displayed. This would indicate
a conflict between the sample rate of the
selected input source and the bass management function. (Operation of the bass
management function requires the source
to have a sample rate of 44.1, 48, 88.2, or
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for Surround
96 kHz.) Selecting a source with a sample
rate of 44.1, 48, 88.2, or 96 kHz will resolve
the issue and normal operation will resume.
Refer to the Technical Notes section of this
user guide for additional details.
Downmix
Two downmix functions allow users to perform “real-world” audio format compatibility
checks. One function allows a surround (5.1)
signal to be “folded down” (mixed) to stereo.
The other allows a stereo signal to be converted to mono. Using the downmix functions simply requires pressing the desired
button. The buttons are set to always “latch”
the functions on and off. An LED is located
adjacent to each button and lights whenever
its respective function is active. The downmix functions always impact the post-fader
surround and stereo monitor outputs. And,
depending on the selected configuration,
they may also impact the pre-fader surround
monitor output.
A specific downmix function can only be enabled when it is applicable for the currently
selected input source. This means that the
surround to stereo downmix function can
only be enabled when surround input A or B
is selected.
The Model 77 associates the state of the
downmix functions with the currently selected input. For example, if surround input A is
the selected input source and the surround
to stereo downmix function is enabled, this
condition will be “remembered” when switching to one of the stereo input sources. Upon
returning to surround input A, the surround
to stereo downmix function will again become active. For details on the exact actions
performed by the downmix functions refer to
Appendix C at the end of this user guide.
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Surround to Stereo
When the surround to stereo downmix
function is enabled the LS, RS, and C
channels associated with a surround
source are combined (“folded down”) with
the L and R signals to create a 2-channel
stereo (left and right) signal. And, depending on the system’s configuration, the LFE
channel may also be combined with the L
and R signals. The resulting stereo signal, sometimes known as LtRt, is routed
to the L and R post-fader surround monitor output channels. Also, whenever the
surround to stereo downmix function is
enabled the C, LS, RS, and SUB monitor
output channels are muted. By utilizing this
downmix function phase relationships and
inter-channel level issues can be quickly
observed.
Stereo to Mono
The stereo to mono downmix function
combines the L and R audio channels to
create a single-channel monaural signal.
This signal is sent out the C surround
monitor output channels while the L, R, LS,
RS, and SUB monitor output channels are
muted.
When a surround source has been selected for monitoring, the surround to stereo
downmix function will automatically enable
whenever the stereo to mono downmix
function is enabled. This ensures that a
user will hear a mono signal created by
folding down all channels associated with
the selected surround input.
Monitor Output General
Functions
Four buttons and one rotary control are
associated with the post-fader surround
and stereo monitor output functions. The
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Studio Technologies, Inc.
for Surround
buttons control operation of the surround
and stereo outputs, reference level, mute
all, and dim functions. The rotary level
control is used to manually set the postfader surround and stereo monitor output
levels. These buttons and the rotary control
do not impact the pre-fader surround and
stereo input C direct monitor outputs.
Surround and Stereo Outputs
The surround/stereo function allows selection between two different loudspeaker
systems. When the surround output is
selected the six post-fader surround monitor output channels are active. The channels associated with the post-fader stereo
monitor output are muted. When the stereo
output is selected the left (L) and right (R)
channels associated with the post-fader
stereo monitor output become active; the
six channels of the post-fader surround
monitor outputs mute.
Remember that the Model 77 Control
Console can be configured to disable
the surround/stereo button. If the button
is pressed and the post-fader stereo
monitor output is not selected, this must
be the case!
Display Current Sample Rate
The surround/stereo monitor output select
button is also used to display the system’s
current sample rate value. Pressing and
holding the surround/stereo button will
cause the current sample rate value to
be displayed: 32.0, 44.1, 48.0, 88.2, 96.0,
176.4, or 192.0. This can be useful during
troubleshooting or just for general interest.
Once the button is released normal display
operation will resume.
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Reference Level
The reference level button sets the postfader surround and stereo monitor output
levels to a preset value. Technical personnel, using a sound-pressure-level (SPL)
meter and precision signal source, should
have set this level to meet the requirements of the specific monitoring environment. The LED associated with the
reference level button will light whenever
the function is active. The 4-digit display
will indicate the reference output level.
Note that the system’s default reference
level is –60.0 dB so “out of the box” the
Model 77 will display –60.0 when reference
level mode is enabled.
How the rotary level control functions
whenever the reference level mode is active depends on a configuration setting.
If the auto reference level off function is
disabled turning the rotary level control will
have no impact on the reference level function; it will remain active. If the auto reference level off function has been enabled
turning the rotary level control will cause
the reference level function to automatically turn off.
The LED associated with the reference
level button can also serve as a calibration aid. If the reference level mode is
not active, whenever the post-fader surround or stereo monitor output levels are
precisely the same as that stored for the
reference value the reference level LED
will flash. This exact level can be reached
through the use of the rotary level control,
either by itself or through the setting of the
rotary level control in conjunction with the
dim function. Whatever path the post-fader
surround and stereo monitor outputs take
to reach the reference level value, it will
cause the reference level LED to flash!
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Mute All
Pressing the mute all button causes the
output channels associated with the postfader surround and stereo monitor outputs
to mute. The 4-digit display indicates the
mute condition by showing four dashes
(– – – –). The mute all button is always set
to “latch” the function on and off. The LED
associated with the mute all button will
light whenever mute all is active. Note that
if mute all is enabled via the remote mute
all function, the mute all LED will flash.
Dim
The dim function is provided for user convenience, allowing the post-fader surround
and stereo monitor output levels to be
reduced by a fixed amount. The Model 77’s
configuration mode allows the dim level
to be selected from among four choices:
–10.0, –15.0, –20.0, or –25.0 dB. Pressing
the dim button will enable the function. The
dim button is always set to “latch” the function on and off. The 4-digit display, when
selected for output level mode, will indicate
the revised post-fader monitor output level.
If the requested “dimmed” output level is
equal to or less than –96.0 dB, the monitor outputs will go into full mute and the
display will show four dashes (– – – –).
When dim is active the post-fader monitor
output level reduction will apply no matter
whether the level is being set by the rotary level control or by the reference level
button. The LED associated with the dim
button will light whenever dim is active. If
dim mode is enabled via the remote dim
function the dim LED will flash.
It’s worth using a few sentences to discuss
the auto dim off function. Whenever dim
is enabled due to the dim button being
pressed, and the rotary level control is
active (reference level mode is not active),
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changing the setting of the rotary level
control will automatically turn off dim. The
auto dim off function is a unique attempt
at protecting the aural health of users. No
longer will there be a heart-stopping blast
of audio when the dim button is pressed,
supposedly to enable dim, but actually
turning dim off because it was already
enabled. It’s hard to explain unless you’ve
experienced this in person—trust us, this
situation can and does happen!
Note that the auto dim off function is not
active whenever dim is enabled due to
the remote dim function being active. This
allows remote control equipment, such
as a talkback system, to reliably dim the
monitor outputs.
Rotary Level Control
The rotary level control is used to manually
adjust the post-fader surround and stereo
monitor output levels. The level control
provides the ability to adjust the post-fader
surround and stereo monitor output levels
over a 70-dB range. Technically the rotary
level control is a 24-step-per-revolution
mechanical encoder. The amount of level
change in dB per step (“click”) will depend
on how quickly the control is turned. When
rotated slowly, each step represents a 0.5dB change in level. In this case, to traverse
the entire level range would require rotating the control more than five full turns. But
the Model 77’s software detects when the
control is rotated more quickly and increases the amount of level change in dB per
step. A little experimentation will allow the
user to acquire a good “feel” for how best
to use the control.
The reference level LED will flash when
the rotary level control sets the output level
to be the same as the stored reference
level. Whenever the rotary level control
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
attempts to set the output level for less than
–70.0 dB, the post-fader surround and stereo monitor output channels will automatically mute. As previously discussed, the
4-digit display indicates the mute condition
by showing four dashes (– – – –).
If the mute all function is active the rotary
level control won’t have an impact on the
post-fader surround and stereo output levels. It’s also not active whenever the reference level function is active, except if the
auto reference level off function has been
enabled.
Channel Mute/Solo
The channel mute/solo functions allow
specific channels to be selected for individual or group mute or “solo” monitoring.
The functions impact the post-fader surround and stereo monitor outputs, taking
place electrically “after” the input source
selection, input delay, downmix, and level
control functions. The relationship between
the mute/solo function and the bass management resources will depend on how the
system has been configured.
The mute/solo mode button and the six
channel mute/solo buttons, along with
associated LEDs, work together to provide
excellent operating flexibility. The channel
mute/solo mode button allows the user to
select between the mute and solo functions.
Going from mute mode to solo mode, or
vice-versa, clears all active mutes or solos.
Pressing the mode button twice is a legitimate means of quickly clearing muted or
soloed channels. To mute or solo a channel
simply requires pressing one of the channel
mute/solo buttons. The buttons function in
a press-to-enable/press-to-disable “latching” mode. Multiple channels can be muted
or soloed at the same time. The LED
Model 760-01/77 User Guide
Studio Technologies, Inc.
associated with any muted or soloed channels is used to indicate that the function is
active.
In most cases the mute/solo function will
be configured to act in a pre-bass management signal flow, creating an “input” mute/
solo function. In this case soloing one channel when bass management is enabled will
result in audio content being reproduced
in both the soloed channel as well as the
subwoofer post-fader monitor output channels. Should the function be configured for
post-bass management mode soloing a
channel will result in only that specific monitor output channel reproducing the audio
content.
Selecting the Solo Mode
As previously discussed in this user guide,
solo operation can be selected between
normal and channel pop. When the normal solo mode has been enabled the solo
LED will light steadily. When the channel
pop solo mode is enabled the solo LED will
flash. It’s easy to change from normal to
pop solo, and vice-versa. Simply press and
hold the mode button and use the surround
to stereo button to select the desired solo
mode. The LED associated with the surround to stereo button displays the active
mode. Refer to Figure 10 for details. The
selected mode will be stored in nonvolatile
memory so a power-down/power-up cycle
will not change the selection.
Input Delay
Two input delay settings, A and B, can
be selected and saved during system
configuration. These are provided for aligning the audio input signals with latencies
associated with video processing and
display systems. During normal operation
of the StudioComm system the active input
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delay, A or B, can be selected. The channel
mute/solo button, stereo to mono button,
and 4-digit display are used to display and
select the input delay. When the mute/solo
button is pressed and held the LED associated with the stereo to mono button indicates whether input delay A or input delay
B is active. The 4-digit display will show the
active delay time in milliseconds. While
pressing and holding the mute/solo button
the stereo to mono button can be pressed
to change the selected input delay. Refer
to Figure 10 for details. The selected input
delay will be stored in nonvolatile memory
so a power-down/power-up cycle will not
change the selection.
Display and Display Mode
The Model 77’s 4-digit LED display
shows the post-fader surround and stereo

monitor output levels as either the amount
of attenuation or the sound pressure
level (SPL). Both will indicate level in dB.
What the digits actually represent will
depend upon how the Model 77 has
been configured.
Display in dB of Attenuation
If configured for the attenuation mode the
display will show the monitor output level
as an attenuation value in reference to
the maximum output. This is in the form
of 0.5-dB steps less than the maximum
of 0.0 dB. So a display of –40.5 would
indicate that the surround or stereo monitor output is set to be 40.5 dB below the
maximum level. As the rotary level control
is moved counterclockwise the output level
will go down and the indicated value will
get more negative.
During normal operation, press and hold the Mute/Solo button
to view and change the solo mode and input delay settings.
This LED displays the current setting
of the solo mode. LED not lit means
normal; LED lit means channel pop.
Press the button to change the mode.
This LED displays the current
setting of the input delay.
LED not lit means input delay A
is selected; LED lit means input
delay B is selected. Press the
button to change the setting.
The display shows the currently
selected input delay in milliseconds.
Figure 10. Solo mode and input delay settings
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Display in dB SPL
If the Model 77 is configured to display the
monitor output level in dB SPL, the 4-digit
display will always show the output level
in positive numbers. These numbers are
intended to represent the sound pressure
level in dB SPL, a figure that should directly
relate to the actual sound pressure level
that the surround or stereo loudspeaker
system is presenting to users. (Typically,
the level value would actually be in dBC,
the C-weighted sound pressure level.)
When the reference level button is enabled,
or the rotary level control is set so that
the reference level has been reached, the
display will typically show something in the
range of 82 to 87 dB. Assuming that the
monitoring environment has been correctly
calibrated, this would indicate that an average listening level of 85 dB, for example,
had been achieved.
Channel Pop Solo Display
As has been previously discussed, the
channel pop solo mode offers a unique way
of sonically highlighting an individual channel. A channel selected for soloing in this
mode will have its level increased while the
other non-soloed channels will be reduced
in level. To highlight this condition the letters
POP will appear in the 4-digit display whenever a channel is actively being soloed in
the channel pop solo mode. This ensures
that a user will understand that the monitor
outputs no longer represent the true interchannel level relationships.
Remote Control Inputs
As previously discussed in the Installation section of this user guide, two remote
control signals can be connected to the
Model 760-01 and then configured for
Model 760-01/77 User Guide
Studio Technologies, Inc.
operation. The functions are remote mute
all and remote dim. When an external
signal activates remote mute all the LED
on the Model 77 associated with the mute
all button will flash. If mute all was already
active when the remote mute all function is
activated, the LED will change from being
steadily lit to flashing.
When an external signal activates remote
dim the LED on the Model 77 associated
with the dim button will flash. If dim was already active when remote dim is activated,
the LED will change from being steadily lit
to flashing.
Model 71 Control Console
The Model 71 Control Console provides a
rotary level control and a limited number of
pushbutton switches and LEDs for control
and status display. The rotary level control
allows adjustment of the post-fader surround and stereo monitor output levels.
Two buttons, along with associated LEDs,
provide access to the dim and reference
level functions. A status LED lights steadily
whenever normal Model 71 operation is
taking place.
Any changes made using the Model 71’s
rotary level control and buttons will be
reflected in the appropriate LEDs and displays on all the connected Model 77 and
Model 71 units. And, as expected, changes
made using a Model 77 will be reflected in
the Model 71’s LEDs.
In some applications it may be desirable to
disable operation of a Model 71’s dim and
reference buttons. An example could be
where non-technical personnel are allowed
only to use the rotary level control. A configuration parameter, previously described
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in the Model 71 Control Console Configuration section, allows button operation to
be disabled.
Technical Notes
Rotary Level Control
The rotary level control is used to manually
adjust the post-fader surround and stereo
monitor output levels. Its operating characteristics are identical to those of the Model
77 Control Console, discussed earlier in
this section.
The Model 760-01 relies on an external
timing reference (sync) source for proper
operation. This can be in the form of an
AES3, word clock, DARS (AES11), bi-level
video, or tri-level video reference signal. In
most cases the sync signal will be connected to the sync input BNC connector
located on the Model 760-01’s back panel.
Alternately, a configuration choice allows
the L/R input of the AES3 source currently
selected for monitoring to also serve as
the system’s timing reference. Whenever
a valid sync signal has been connected
to the Model 760-01 the sync status LED,
located on the unit’s front panel, will light.
The sample rate of the monitor output
channels will reflect the rate of the sync
input and, if a video sync source is utilized,
the configured rate.
Dim
The dim function allows the post-fader surround and stereo monitor output levels to
be reduced by a fixed amount. Its operating characteristics are identical to those of
the Model 77 Control Console, discussed
earlier in this section.
An indication is provided should the dim
button be pressed when button operation
has been disabled. Its associated LED will
flash briefly but no operating change will
occur. The LED will continue to display the
status of the dim function as selected by
other Model 77 and Model 71 units.
Reference Level
The reference level button sets the postfader surround and stereo monitor output
levels to their preset values. The operating characteristics are identical to those of
the Model 77 Control Console, discussed
earlier in this section.
An indication is provided should the reference button be pressed when button
operation has been disabled. The associated LED will flash briefly but no operating
change will occur. The LED will continue
to display the status of the reference level
function as selected by other Model 77 and
Model 71 units.
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Loss of Sync
If a valid sync signal is not present several visual indications are provided. On
the Model 760-01 the sync status LED will
flash. On all connected Model 77 Control
Consoles the 4-digit LED display will cease
normal operation, instead alternating
between the words no and sync. When
a valid sync signal is again connected
the Model 760-01’s sync status LED will
light steadily. On the Model 77 units the
word sync will momentarily be displayed
followed by a brief display of the monitor
output sample rate. The sample rate will
display as 32.0, 44.1, 48.0, 88.2, 96.0,
176.4, or 192.0, reflecting the impact of the
sync source rate and the Model 760-01’s
configuration.
If during normal operation the sync source
changes from one valid rate to another a
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
visual indication is provided. On the Model
77 units the new sample rate—32.0, 44.1,
48.0, 88.2, 96.0, 176.4, or 192.0—will
momentarily be displayed.
Any time that a valid sync signal is not
connected to the Model 760-01 the digital
monitor outputs will automatically revert
to an internally generated sample rate of
48 kHz with no digital audio content present. This audio “black” signal will allow most
connected equipment to continue to function correctly, of course with no meaningful
audio signal present. As soon as a valid
sync signal is again connected to the Model
760-01 the monitor outputs will automatically switch to their correct sample rate and
audio signals will again be present.
Power Down
Great care was taken in the Model 760-01’s
design to minimize the chance that clicks,
pops, or other objectionable audio signals
will be present on the monitor outputs.
A power-down circuit supplies the main
microcontroller integrated circuit with an
indication that a power loss is imminent.
When this condition is detected the monitor
outputs will switch to silence (digital audio
“black”) in preparation for a complete loss
of signal.
Power-Up Messages
Upon mains power being applied to the
Model 760-01 all connected Model 77 units
will go through a power-up sequence. The
sequence starts by each of the individual
LEDs lighting in a “walk-through” sequence.
Then the 4-digit display tests all its LED
segments. Finally, a set of messages provide details on the specific Model 77 and
connected Model 760-01 software versions:
Model 760-01/77 User Guide
Studio Technologies, Inc.
1. Displays 77
2. Displays Model 77’s software version
3. Displays Model 77’s unit address
(A1, A2, A3, or A4)
4. Displays 760
5. Displays Model 760-01’s main
software version
6. Displays FPgA
7. Displays Model 760-01’s logic
device (FPGA) software version
After a successful system power-up
sequence normal operation will then
commence.
Error Codes Err1 and Err2
Should a problem be encountered during
power up one of two error codes may show
on the Model 77’s 4-digit display. If Err1
displays it indicates that communication
is not taking place with the Model 760-01.
The most likely cause would be incorrect wiring of the data pair linking the two
units. Err2 indicates that the Model 760-01
is having problems with its internal logic
device. (A high-speed field-programmable
gate array (FPGA) serves as the digital
“heart” of the Model 760-01 and without
it no audio activity can occur.) The only
way to remedy this condition is to first try
removing and reconnecting mains power.
(And that’s a long-shot as to whether it
would accomplish anything.) If the error
code continues to be displayed the Model
760-01 must be returned to the factory for
service. Note that for the vast majority of
StudioComm systems neither of these error codes, especially Err2, will ever appear.
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Error Code Err3
As previously discussed in this user guide,
the bass management function only supports input signals whose sample rate is
44.1, 48, 88.2, or 96 kHz. If during normal
operation this condition is not met, it’s possible that Err3 will display and the mute all
function will be automatically enabled. This
will occur if the bass management function
is configured to be enabled for either or both
the surround and stereo post-fader monitor
outputs and an input with a non-compatible sample rate has been selected. In this
scenario, selecting a different input with a
sample rate of 44.1, 48, 88.2, or 96 kHz will
return the system to normal operation.
Sample Rate Conversion
(SRC)
Circuitry associated with stereo input C can
provide sample rate conversion (SRC) capability. A digital audio signal connected to that
input can have its sample rate and timing
re-synchronized to match the Model 76001’s internal timing. While it would be nice to
proclaim that the engineers at Studio Technologies came up with a unique and exotic
circuit to perform this function it’s really not
the case. Several semiconductor companies
provide “single-chip” SRC solutions and an
excellent one from AKM was selected for
the Model 760-01. The technical capabilities of the Model 760-01’s SRC function
is stated in this way: the sample rate of an
input signal can range from 1/6 to six times
the Model 760-01’s output sample rate, with
the additional restriction that it must be no
less than 8 kHz and no more than 216 kHz.
The Model 760-01’s output sample rate is
determined by the selected timing reference
(sync) signal and, if required, a configured
value. If a word clock, DARS (AES11), or
Issue 3, April 2015
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AES3 signal is the designated sync source
its rate will be the Model 760-01’s output
sample rate. If a video sync signal is connected, the Model 760-01’s sample rate is
selected as part of the configuration process.
So in practice what can the SRC function
accomplish? If the output sample rate is
48 kHz then a signal connected to stereo
input C can have a sample rate from 8
to 216 kHz. Or, as another example, if
the Model 760-01’s output sample rate
is 96 kHz a signal connected to stereo
input C can have its sample rate range
from 16 to 216 kHz.
As useful as allowing one disparate
sample rate to be converted to another,
it may be the ability of the Model 760-01’s
SRC function to re-synchronize a signal
that proves most valuable. For example,
in typical post-production and broadcast
applications all signals will have a sample
rate of 48 kHz. A Model 760-01 and all of
its normally connected input signals will be
“locked” to the main timing reference signal
that supports the 48 kHz sampling rate.
But, as an example, a signal associated
with a portable device, while at a 48 kHz
sampling rate, may not be synchronized
(“genlocked”) to the “house” reference.
Connecting this signal to stereo input C
will cause the SRC function to “lock” it to
the Model 760-01’s rate, thus allowing it to
be monitored over a loudspeaker system.
In addition, the stereo input C direct monitor output can be connected to other devices that find need for the now-synchronized
signal. In some cases it may be useful to
connect the stereo input C direct monitor
output to the input of a signal router, allowing an entire facility to access the signal.
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Model 760-01 to Control
Console Connections
Channel Status, User, and
Validity Bits
Figure 7 gives a detailed description
of the signals that connect the Model
760-01 Central Controller to the one or
more Model 77 or Model 71 Control Consoles. The Model 760-01 provides 12 Vdc
for use by the control console’s circuitry.
The DC output is current-limited to minimize the chance that a short-circuit condition will damage the Model 760-01’s
circuitry. An asynchronous, bi-directional
data interface links the connected units.
The RS-485 hardware connection scheme
operates at a rate of 115.2 kbit/s and uses
an 8-N-1 data format. The Model 760-01
communicates with each Model 77 and
Model 71 unit 20 times per second, receiving button and rotary level control information and sending LED and 4-digit display
status data.
The non-audio bits that are part of the
AES3 digital audio monitor output channel
data are actively controlled by the Model
760-01’s software. The Channel Status
bits use the Professional Use of Channel
Status block. They indicate a word length
of 24 and the current sample rate. The correct CRC is also calculated and inserted.
The User bits are always set to 0. When
a valid timing reference (sync) source is
recognized by the system the Validity bits
will be set to 1.
The Model 760-01’s hardware is capable
of routing the C/U/V bit information from
any of the L/R inputs, as well as the sync
input, to the main logic device (FPGA)
and then on to the digital audio transmitter
(DIT) integrated circuits. This is provided
for future use and is not active at this time.
“Hot” Disconnection of
Control Consoles
There’s no problem relocating one or more
Model 77 or Model 71 Control Consoles
while the StudioComm system is operating. You can disconnect the 9-pin interconnecting cable, move the unit (or units), and
then reconnect without issue. Upon disconnection of all control consoles the Model
760-01 Central Controller will mute the
internal digital audio channels as well as
saving the current operating parameters.
No clicks, pops, or other noises will occur
when the Model 77 or Model 71 units are
again connected. The control consoles
will go through their standard power-up
sequence and then normal operation will
resume.
Model 760-01/77 User Guide
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Issue 3, April 2015
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for Surround
Specifications
Model 760-01 Central Controller
General Audio:
Supported Sample Rates: 32, 44.1, 48, 88.2, 96,
176.4, and 192 kHz
Word Length: 24 bits maximum
Internal Processing: 32 bits
Input-to-Output Latency: two samples (e.g., 0.042
milliseconds @ 48 kHz sample rate)
Digital Audio Inputs: 5 (18 audio channels)
Configuration: two surround (5.1) and three stereo
Type: balanced AES3 (110 ohms, 5 Vpp)
Connector—Surround Inputs and Stereo Inputs
A & B: 25-pin female D-subminiature (DB-25F),
AES59-2012-compliant
Connector—Stereo Input C: 3-pin female XLR
Sample Rate Conversion (SRC):
Application: available on Stereo Input C
Configurable Input Delay: 0 to 340 milliseconds
@ 48 kHz sample rate (scales up or down depending on actual sample rate)
Post-Fader Monitor Output Level Offsets: each
surround and stereo channel independently adjustable in 0.5-dB steps over a ±12-dB range
Bass Management:
Supported Sample Rates: 44.1, 48, 88.2, and
96 kHz only
Crossover Frequency and Type: –6 dB @ 40, 50,
60, or 80 Hz, symmetrical for low-pass and highpass filters, maximally flat
Filter Slope: 12-per-octave or 24 dB-per-octave
Overall Operation: independent on/off selectable
for surround and stereo post-fader monitor outputs
Downmix:
Surround to Stereo and Stereo to Mono
Control Console Interface:
Type: RS-485, 115.2 kbit/s, 8-1-N
Polling Interval: 80 milliseconds, nominal
Input Sample Rate Range: 8 to 216 kHz, limited
to 1/6 to 6 times the output sample rate
Power: 12 Vdc, 500 mA maximum
Latency: 1 millisecond, nominal
Remote Control Inputs: 2
Functions: remote mute all, remote dim
Sync Source: configured to follow L/R of currently
selected input or signal connected to sync input
Sync Input:
Compatible Sources: word clock, DARS (AES11),
bi-level video, tri-level video
Jitter: 4 ns pp maximum
Connector: BNC (per IEC 60169-8 Amendment 2)
Termination: 75 ohms, selectable on/off
Digital Monitor Outputs: 16 (8 pairs)
Configuration: organized as two surround (5.1)
and two stereo
Dynamic Range: >135 dB
Type: balanced AES3 (110 ohms, 5 Vpp)
Connector: 25-pin female D-subminiature
(DB-25F), AES59-2012-compliant
Connector: 9-pin female D-subminiature (DE-9F)
Type: 3.3 Vdc logic, activates on closure to system
common
Connector: 9-pin female D-subminiature (DE-9F)
AC Mains:
Requirement: 100 to 240 V, +10/–15%, 50/60 Hz,
15 W maximum
Connector: 3-blade, IEC 320 C14-compatible
(mates with IEC 320 C13)
Dimensions:
19.00 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
7.00 inches deep (17.8 cm)
Mounting: one space (1U) in a standard 19-inch
rack
Weight: 3.6 pounds (1.6 kg)
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Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Model 77 Control Console
Model 71 Control Console
Application: up to four Model 77 Control Consoles can be connected to a Model 760-01 Central
Controller
Application: up to three Model 71 Control
Consoles can be connected to a Model 760-01
Central Controller
Power: 12 Vdc nominal (9 Vdc minimum), maximum current 100 mA, provided by Model 760-01
Central Controller
Power: 12 Vdc nominal (9 Vdc minimum), maximum current 35 mA, provided by Model 760-01
Central Controller
Control Data:
Type: RS-485
Control Data:
Type: RS-485
Data Rate/Format: 115.2 kbit/s, 8-N-1
Data Rate/Format: 115.2 kbit/s, 8-N-1
Connector: 9-pin female D-subminiature (DE-9F)
Connector: 9-pin female D-subminiature (DE-9F)
Dimensions (Overall):
7.20 inches wide (18.3 cm)
2.20 inches high (5.6 cm)
5.40 inches deep (13.7 cm)
Dimensions (Overall):
3.20 inches wide (8.1 cm)
2.20 inches high (5.6 cm)
4.10 inches deep (10.4 cm)
Weight: 1.7 pounds (0.8 kg)
Weight: 0.8 pounds (0.4 kg)
Specifications and information contained in this
User Guide subject to change without notice.
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Appendix A—Connection Pin-Out
Charts
Channel
Signal
High (+)
Signal
Low (–)
Shield
Connections
Channel
Signal
High (+)
Signal
Low (–)
Shield
Surround Input A L/R
1
24
12
25
Pre-Fader L/R
1
24
12
25
Surround Input A C/LFE
2
10
23
11
Pre-Fader C/SUB
2
10
23
11
Surround Input A LS/RS
3
21
9
22
Pre-Fader LS/RS
3
21
9
22
Stereo Input A
4
7
20
8
Stereo Input C Direct
4
7
20
8
Surround Input B L/R
5
18
6
19
Post-Fader L/R
5
18
6
19
Surround Input B C/LFE
6
4
17
5
Post-Fader C/SUB
6
4
17
5
Surround Input B LS/RS
7
15
3
16
Post-Fader LS/RS
7
15
3
16
Stereo Input B
8
1
14
2
Post-Fader Stereo
8
1
14
2
Connections
Notes: 1) All signals transformer-coupled digital audio;
balanced AES3 (110 ohms, 5 Vpp) compatible.
Notes: 1) All signals transformer-coupled digital audio;
balanced AES3 (110 ohms, 5 Vpp) compatible.
2) Connector type on Model 760-01 is 25-pin female
D-subminiature (DB-25F). Installer must provide male
(DB-25M). Connector uses 4-40 threaded inserts for
locking with mating plug.
2) Connector type on Model 760-01 is 25-pin female
D-subminiature (DB-25F). Installer must provide male
(DB-25M). Connector uses 4-40 threaded inserts for
locking with mating plug.
3) Wiring scheme follows AES59-2012 convention.
Standard TASCAM-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
3) Wiring scheme follows AES59-2012 convention.
Standard TASCAM-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Connections for Surround A, Surround B,
Stereo A, and Stereo B Digital Inputs
Connections for Digital Monitor Outputs
Signal
Direction
Signal
Shield
Data + (RS-485)
1
To/From Models 77/71
6
To/From Models 77/71
2
To/From Models 77/71
Data Shield
Pin
1
Remote Mute All
5
Input
Data – (RS-485)
Remote Dim
6
Input
Data Shield
Remote Spare 1
8
Input
Remote Spare 2
9
Input
Remote Input Common
4
Common
Note: Connector type on Model 760-01 is 9-pin female
D-subminiature (DE-9F). Connector uses 4-40
threaded inserts for locking with mating plug.
Connections for Remote Control Inputs
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Pin
Direction
DC + (12 V)
4
To Models 77/71
DC – (12 V Return)
9
To Models 77/71
DC Power Shield
5
To/From Models 77/71
Note: Connector type on Model 760-01 is 9-pin female
D-subminiature (DE-9F). Connector uses 4-40 threaded
inserts for locking with mating plug.
Connections between Model 760-01 and
Model 77 and Model 71
Model 760-01/77 User Guide
Studio Technologies, Inc.
for Surround
Appendix B—Sync Input Sources
The Model 760-01’s sync input has been tested and confirmed for correct operation with the
following sync signals:
Word Clock: Square wave signal with rate of 32, 44.1, 48, 88.2, 96, 176.4, or 192 kHz.
DARS (AES11) or AES3: Signal with sample rate of 32, 44.1, 48, 88.2, 96, 176.4, or
192 kHz.
Bi-Level and Tri-Level Video: See table below.
Video Format
Video Format, continued
NTSC (“Black Burst”)
1035i/59.98 Hz
PAL (“Black Burst”)
1035i/60 Hz
525i/59.94 Hz
1080i/50 Hz
525p/59.94 Hz
1080i/59.94 Hz
625i/50 Hz
1080i/60 Hz
625p/50 Hz
1080p/23.98 Hz
720p/23.98 Hz
1080p/24 Hz
720p/24 Hz
1080p/25 Hz
720p/25 Hz
1080p/29.97 Hz
720p/29.97 Hz
1080p/30 Hz
720p/30 Hz
1080psf/24 Hz
720p/50 Hz
1080psf/23.98 Hz
720p/59.94 Hz
720p/60 Hz
Model 760-01/77 User Guide
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Issue 3, April 2015
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Appendix C—Downmix Formulas
The following provides a summary of the action performed when the downmix modes
are active. Signals at unity gain unless noted. 1 = 0 dB; 0.707 = –3 dB; 0.5 = –6 dB;
0.35 = –9 dB; 0 = full attenuation.
Surround to Stereo
L = (1 or 0.707)L + (0.707 or 0.5)C + (0.707 or 0.5)LS +(0 or 0.5)LFE
R = (1 or 0.707)R + (0.707 or 0.5)C + (0.707 or 0.5)RS + (0 or 0.5)LFE
C, LFE, LS, and RS monitor outputs mute
Stereo to Mono
With a stereo input selected the result is:
C = 0.707L + 0.707R
L, R, LS, RS, and LFE monitor outputs mute
With a surround input selected the surround to stereo downmix function automatically
enables resulting in:
C = (0.707 or 0.5)L + (0.707 or 0.5)R + (0.707 or 0.5)C + (0.5 or 0.35)LS
+ (0.5 or 0.35)RS + (0 or 0.5)LFE
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Model 760-01/77 User Guide
Studio Technologies, Inc.
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