for Surround - Studio Technologies

for Surround - Studio Technologies
for Surround
Model 76D Central Controller and
Model 77 Control Console
User Guide
Issue 4, April 2011
This User Guide is applicable for systems consisting of:
Model 76D: serial number M76D-00151 and later with software version 3.01 and higher;
Model 77: serial number M77-00265 and later with software version 3.01 and higher
© 2011 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50230-0411, Issue 4
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for Surround
Table of Contents
Introduction ................................................................... 5
Installation .................................................................... 8
Configuration ................................................................15
Operation ......................................................................34
Technical Notes ............................................................40
Specifications ...............................................................43
Appendix A—Connection Pin-Out Charts ....................45
Appendix B—Sync Input Sources ................................46
Model 76D/77 User Guide
Studio Technologies, Inc.
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Issue 4, April 2011
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Model 76D/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 76D
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, postproduction, and broadcast facilities. And
with audio-with-picture applications becoming so prevalent, additional monitoring
challenges have arisen. Studio Technologies has addressed these needs with the
StudioComm for Surround Model 76D
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, downmix and mute/solo
functions, 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 an operator’s location,
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Studio Technologies, Inc.
allowing fingertip selection of all monitoring functions. Numerous LED indicators
provide complete status information. A
4-digit numeric display indicates the postfader 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.
While many installations will use only one
Model 77 Control Console, 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 76D provides
power for all connected Model 77 or Model
71 units.
The core of this StudioComm for Surround
system is the Model 76D Central Controller. The one-rack-space unit contains
circuitry that supports digital audio inputs,
digital monitor outputs, processing, and
the user interface. The Model 76D provides
two surround (5.1) and three stereo
digital audio inputs. These unbalanced
digital inputs are AES3id/SMPTE 276Mcompliant; sources of this type are
ubiquitous in most post-production and
broadcast 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
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delays in an associated video path. A number of different signals can serve as the
Model 76D’s digital audio timing reference.
For synchronization with a master timing reference a dedicated source of word
clock, DRS (AES11), bi-level video, or trilevel video can be connected. Alternately,
the L/R connection of the actively selected
surround or stereo input source can serve
as the timing reference.
For installation flexibility the monitor outputs
can be configured for compatibility with
equipment that requires AES3 (“balanced”)
or AES3id (“unbalanced”) digital audio signals. When selected for AES3 compatibility
the output impedance is 110 ohms with a
signal level of 5 volts peak-to-peak (Vpp).
For AES3id operation the impedance is
75 ohms and the level is 1 Vpp.
Great care was taken in designing the system’s architecture, ensuring that the character of the audio input signals is preserved.
All audio processing is performed in 32 bits
using a high-speed field-programmable
gate array (FPGA) integrated circuit.
A range of surround (5.1) and stereo digital
monitor outputs are provided. The postfader 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 Model 76D occupies one space (1U)
in a standard 19-inch rack. Digital audio
sources are interfaced with the Model 76D
using nine BNC connectors. A tenth BNC
connector is used by the sync source. Digital monitor output signal connections are
Figure 1. Model 76D Central Controller Front Panel
Control console
status LED
Sync status
LED
Figure 2. Model 76D Central Controller Back Panel
AC mains input
To/from
Models 77 &
71 Control
Consoles
Remote control
inputs
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Digital
monitor
outputs
Sync
Input
Surround Input B
Stereo
Input C
Stereo Input A and
Stereo Input B
Surround Input A
Model 76D/77 User Guide
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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
made using a 25-pin D-subminiature connector. One 9-pin D-subminiature connector is used to connect the Model 76D with
up to 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 76D, with an acceptable
range of 100 to 230 volts, 50/60 Hz.
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”).
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
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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 operator 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
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the post-fader surround and stereo monitor output channels to be simultaneously
muted. The channel mute/solo section
provides post-fader 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 in 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
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 5.1 to stereo downmix function is used
to create a stereo signal from the selected
surround (5.1) source. The stereo to mono
downmix function allows audio on the left
and right 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.
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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.
Installation
In this section you will be installing the
Model 76D 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 76D. AC mains power will be
connected to the Model 76D. For advanced
applications up to three additional Model 77
or Model 71 Control Console units can be
connected to the Model 76D.
System Components
The main shipping carton contains one
each of the following: Model 76D 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.
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Mounting the Model 76D
The Model 76D Central Controller requires
one space (1U) in a standard 19-inch
(48.3 cm) equipment rack. Secure the
Model 76D 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 to
connect the Model 76D 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
nine BNC jacks and one 25-pin D-subminiature connectors. All the connectors are
located on the Model 76D’s back panel.
Refer to Figure 2 for a detailed view of
these jacks and the connector.
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 function.) 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
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maintain a common sample rate and timing reference. Having all signals “locked”
together helps to ensure proper handling
by the Model 76D’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 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 guide
for a detailed review of the SRC capability.
Nine BNC jacks on the Model 76D’s back
panel are used to interface with the 18
channels associated with the digital audio
signal sources; each BNC connector carries two audio channels. The digital audio
inputs are intended for connection with
unbalanced digital audio sources that are
compatible with the AES3id standard. In
broadcast or post-production environments
these signals may also be referred to as
following the SMPTE 276M standard. This
signal type has a nominal impedance of
75 ohms with a nominal signal level of
1 Vpp. As expected, these digital audio
sources should be provided in the form of
coaxial cables with BNC plugs attached.
Balanced AES3 digital audio signals can
also be used with the Model 76D’s inputs
if external coupling transformers (“baluns”)
are utilized. These impedance-matching
(110 ohms to 75 ohms) and level-attenuating transformer assemblies typically provide a 3-pin female XLR connector on their
input and a female BNC connector on their
output.
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Monitor Outputs
The 25-pin D-subminiature connector
labeled Digital Monitor Outputs provides
access to the Model 76D’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
conversion (SRC) and input delay circuitry.
The impact made by these functions will
depend on the specific input signal and the
Model 76D’s configuration settings.
For flexibility the monitor outputs are transformer-coupled and can be configured to
act as AES3 or AES3id digital audio sources. The monitor outputs are configured in
two groups with separate choices available
for the pre-fader surround/stereo input C
direct group and post-fader surround/postfader stereo group. When a group is set for
AES3 (110 ohms/5 Vpp) the signals are
compatible with AES3 interfaces. Signals
of this type are normally interconnected
using shielded twisted-pair cable terminated with 3-pin XLR connectors. When a
group is configured for AES3id (75 ohms/
1 Vpp) the source impedance and signal
level are compatible with the requirements
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of AES3id interfacing. These signals are
typically interconnected using coaxial
cable terminated with BNC connectors. For
details on how a Model 77 Control Console
is used to select the monitor output types
refer to the Configuration section of this
user guide.
A cable assembly with a 25-pin D-sub plug
(male) on one end and the desired connectors on the other end will be used for
connecting to the digital monitor outputs.
The D-subminiature connector follows the
TASCAM® 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/AES3id digital audio signals
this allows support for 16 audio channels;
eight interfaces each supplying two audio
channels.
A wiring assembly prepared for the Model
76D’s monitor outputs, when configured for
AES3 (110 ohms/5 Vpp), would be identical to that of a D-88-style output assembly. An assembly of this type would have
a male 25-pin D-subminiature connector
(DB-25M) on one end and eight 3-pin male
XLR connectors on the other. A wiring
assembly prepared for the Model 76D’s
monitor outputs, when set for AES3id
(75 ohms/1 Vpp), would typically have
eight BNC plugs attached.
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 XLR plug (male) will be used. In this
case the + terminal would go to pin 2 of
the XLR, the – terminal to XLR pin 3, and
the shield terminal to XLR pin 1.
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
For compatibility with AES3id unbalanced
digital audio signals connect the D-sub’s
+ terminal as signal high, and both the
– and shield terminals as the signal low/
shield. When terminating to a BNC plug the
D-sub’s + terminal should connect to the
center pin; the – and the shield connections should go to the “body” of the BNC
plug. To clarify, for optimal operation it is
best to connect both the – and shield connectors together directly on the D-sub plug,
rather than at the BNC end of the interface
assembly. Note that the output circuitry is
transformer-coupled so it is possible to just
connect to the + and – terminals and still
experience correct operation. This would
leave the shield connection unterminated.
Refer to Figure 4 or Appendix A for the
exact connection details. Note that unlike
a D-88-style assembly, the two threaded
fasteners associated with the Model 76D’s
D-sub connectors use 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
Connections
TASCAM® Signal
Channel High (+)
Pre-Fader L/R
Signal
Low (–)
Shield
1
24
12
25
Pre-Fader C/LFE
2
10
23
11
Pre-Fader LS/RS
3
21
9
22
Stereo Input C Direct
4
7
20
8
19
Post-Fader L/R
5
18
6
Post-Fader C/LFE
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;
selectable for AES3 or AES3id compatibility.
2) Connector type on Model 76D is 25-pin
D-subminiature female (DB-25F). Installer must
provide male (DB-25M). Connector uses 4-40
threaded inserts for locking with mating plug.
3) Wiring scheme follows TASCAM D-88 convention.
Standard D-88-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Figure 4. Connections for Digital Monitor Outputs
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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.
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.
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 76D 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
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timing reference signal to the Model 76D’s
sync input connector. The connected sync
signal must maintain a stable relationship
between itself and the digital audio inputs.
The actual sync source can be in one of
several formats: word clock, DRS (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
audio sources. DRS (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 or AES3id 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 high-definition (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 76D 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.
The external sync reference source is connected to the sync input BNC connector
located on the Model 76D’s back panel.
For flexibility this input can be configured
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to be high-impedance (“floating”) or terminated with an impedance of 75 ohms.
A sync source that is dedicated for use by
the Model 76D’s sync input will typically
have input termination enabled. If the
sync signal connected to the Model 76D 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.
Remote Control Inputs
Support is provided for two remote control input functions: remote mute all and
remote dim. These functions only impact
the post-fader surround and stereo monitor
outputs. The Model 76D’s inputs use logic
gates, “pulled up” to +5 volts DC 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 5 or Appendix A for the exact connection details. Note that pin 4 (remote
common) connects to the Model 76D’s
internal circuit common connection as well
as to the Model 76D’s chassis and mains
earth connections. Figure 5 also shows
two spare remote control inputs (pins 8
and 9). These are provided for future applications and should remain unconnected.
This connector also allows access to an
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Signal
Pin
Direction
Signal
Data + (RS-485)
Data + (RS-485/RS-422)
7
Not used
Data – (RS-485/RS-422)
2
Not used
Data Shield
1
Shield
Remote Mute All
5
Input
Remote Dim
6
Input
Remote Spare 1
8
Input
Remote Spare 2
9
Input
Remote Common
4
Common
Pin
Direction
1
To/From Models 77/71
Data – (RS-485)
6
To/From Models 77/71
Data Shield
2
To/From Models 77/71
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 76D is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Note: Connector type on Model 76D is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Figure 6. Connections between Model 76D and
Model 77 and Model 71
Figure 5. Connections for Remote Control
Inputs
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
76D’s connector pin-out scheme was designed to allow creation of an interconnecting cable which uses commonly 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.
RS-485 data interface. This interface is not
supported in the Model 76D and, as such,
pins 7 and 2 should remain unterminated.
Connecting the Model 76D 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 76D
Central Controller. This is used to interface
the unit with Model 77 Control Consoles.
Refer to Figure 6 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 76D with the
Model 77 units. A cable is included in the
shipping carton. The cable implements
all nine connector pins in a one-to-one
manner.
Should an interconnecting cable of a different length be required there’s no problem
for one to be fabricated and used. While it
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A few simple calculations are required to
determine the maximum cable length when
connecting a Model 76D 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
76D to a Model 77. The Model 76D supplies 12 volt DC with a maximum current
of 500 milliamperes.
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The Model 77 requires a minimum of
9 volts DC, 100 milliamperes, 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
76D supplies 12 volts and the Model 77
requires 9 volts minimum, this directly
leads to a 3 volt DC 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 calculating the voltage drop. If it’s greater than
3 volts your cable is too long or the wire
gauge is too small.
Additional Control Consoles
Some installations may benefit from the
Model 76D’s ability to be controlled by
additional control consoles. At least one
Model 77 Control Console must be connected to the Model 76D Central Controller. After this requirement has been met up
to three additional Model 77 or Model 71
Control Consoles can also be connected
and powered by the Model 76D.
When connecting multiple control consoles
to a Model 76D all nine pins of each interconnecting cable can be connected in
parallel (“multed”). Using this arrangement
the data and 12 volt DC 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 –).
Issue 4, April 2011
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To make installation simple, a “bus” cable
assembly can be created using a short
length of ribbon cable with one male and
multiple female 9-pin 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 76D to Model 77 cable length are
discussed. Note the required current for a
Model 77 is 100 milliamperes while a Model 71 requires only 35 milliamperes. It’s
important to review this information prior to
creating the interconnection scheme to be
used for installing multiple Model 77 units.
AC Mains Power
The Model 76D operates directly from AC
mains power of 100 to 230 volts, 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
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Safety Warning: The Model 76D
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 76D 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 76D’s main logic
device. After just a few seconds initial 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 76D.
All connected Model 71 units will also go
through a power-up sequence after mains
power is applied to the Model 76D. Each of
the Model 71’s three LEDs will light momentarily. After these LEDs have been lit,
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Studio Technologies, Inc.
the device address will be shown briefly
using the dim and reference level LEDs, as
shown in Figure 7 in the Operation 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 76D. 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 76D’s front panel will continue
to flash in cadence indefinitely. On the
Model 77 units a diagnostic code may
be displayed. Refer to the Technical Notes
section of this user guide for details.
Only after the Model 76D 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
76D 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,
one configuration choice is available for
each of the connected Model 71 Control
Consoles.
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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 (unique for
each unit)
• Stereo Input C Sample Rate Converter
• Post-Fader Stereo Monitor Output
• Sync Source
• Sync Input Termination
• Audio-Synced-to-Video Sample Rate
• Monitor Output Types
• Reference Level
• Overall Display Mode
• Reference Level in dB SPL
• Auto Reference Level Off
• Dim Level
• Remote Inputs
• Input Delay
• LFE Downmix Mode
• Pre-Fader Surround Monitor Output
Mode
• Channel Pop Solo Mode Offset Levels
• 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.
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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 D-sub connector. On any connected Model 77 pressing and holding this
button for two seconds places both this
specific unit and the Model 76D into their
configuration modes. Other connected
Model 77 and Model 71 units will enter a
standby mode. When the Model 76D 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.
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 configure the 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 configure 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
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
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 76D Central Controller as well as
the Model 77 and Model 71 Control Consoles. However, only the individual device
address is stored in each Model 77 and
Model 71. All other configuration parameters are stored in the Model 76D.
Model 77 Device Address
A unique device address must be assigned
to each Model 77 that is connected to a
Model 76D. 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.
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Studio Technologies, Inc.
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 with the others
connected to the Model 76D, 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.
Post-Fader Stereo Monitor
Outputs
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 an operator. In applications where stereo monitor loudspeakers are not connected to the post-fader stereo monitor output,
the output can be disabled. This can minimize confusion, preventing an operator
from attempting to select the post-fader
stereo monitor output.
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Sync Source
The Model 76D requires that the designated external timing reference (sync) be
defined. Three of the choices—word clock,
DRS, 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 76D 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 76D’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.
Pre-Fader Surround/Stereo
Input C Direct Monitor Output
Type
To meet the needs of specific installations
the nominal impedance and level characteristic of the pre-fader surround and
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stereo input C direct monitor outputs can
be selected. They are selected as a group;
configuration of individual outputs is not
provided. If the output signals are going
to be connected to balanced AES3 inputs
then the setting that provides a source impedance of 110 ohms and a nominal 5 Vpp
output level would be appropriate. If the
output signals are going to be connected
to unbalanced AES3id inputs then the setting that provides a 75 ohm source impedance and a nominal output level of
1 Vpp would be correct.
Post-Fader Surround/Stereo
Monitor Output Type
The source impedance and output level of
the post-fader surround and stereo monitor outputs, as a group, can be configured.
The information previously provided concerning configuring the pre-fader surround/
stereo input C direct monitor output type
also applies to these outputs.
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 postfader 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:
1. Set up a precision sound pressure
level (SPL) measuring device at the
desired listening location.
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
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.
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.
3. Use the Model 77 Control Console to
select the input source that contains
the desired reference signal source,
e.g., pink noise.
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.
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.
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 configure button for two seconds.
The new reference level is now stored
in the Model 76D’s nonvolatile memory.
Only by repeating the entire procedure
can the value be changed.
Model 76D/77 User Guide
Studio Technologies, Inc.
Overall Display Mode
The Model 77’s 4-digit numeric display
can be configured to display the post-fader
surround and stereo 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 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). Used in conjunction with the reference level in dB SPL
configuration and the stored reference
level, 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
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implement the SPL display mode, it can
offer an enhanced experience for StudioComm users.
surround and stereo monitor outputs’ current
level. There are four dim level values available: –10.0, –15.0, –20.0, and –25.0 dB.
Reference Level in dB SPL
Remote Mute All
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
surround or stereo monitor outputs are at
their 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, 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.
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.
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
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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 signals.
The selected time delay applies to all input
signals and cannot be applied selectively.
The 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 192 kHz sampling the time
range is 0 to 85 milliseconds. Selecting a
delay of 240 will result in a time delay of
60 milliseconds.
LFE Downmix Mode
By default, when the 5.1 to stereo downmix
function is active the LFE channel associated with a surround input is muted. This
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Studio Technologies, Inc.
for Surround
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 part of the downmix signal flow.
When the LFE downmix mode is enabled,
if surround input A or B is the currently
selected input and the 5.1 to stereo downmix function is active, the LFE signal level
is reduced in level by 6 dB and added to
both the left and right output channels. As
expected, even when the LFE downmix
mode is active the LFE output channel will
still mute when 5.1 to stereo downmix is
active.
Pre-Fader Surround Monitor
Output Mode
The pre-fader surround monitor output can
be configured as to its place in the Model
76D’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 an operator 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, level meters were connected to
the pre-fader surround monitor outputs. In
this scenario an operator would want to
visually observe the actions that the downmix functions impart on the signals.
Model 76D/77 User Guide
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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.
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
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
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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!
Figure 7. Model 71 Control Console Front and
Back Panels
Address
Dim LED
Reference Level LED
A1
OFF
OFF
A2
OFF
ON
A3
ON
OFF
A4
ON
ON
Model 71 Control Console
Configuration
Figure 8. Model 71 Device Address Chart
The only configuration choice available on
a Model 71 is its device address. It must be
selected so as not to conflict with the device address of any other 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 Figures 7 and 8 for details.
A small button is located on the back of
each Model 71 Control Console, adjacent
to the 9-pin D-sub connector. Pressing and
holding this button for two seconds places
this specific unit in its configuration mode;
normal operation of the Model 76D 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.
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Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Instead the status LED will blink to indicate that configuration mode is active. 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.
To leave the configuration mode and return
a Model 71 to normal operation requires
one last action; again press and hold its
configure button for two seconds. The
selected device address will be stored in a
nonvolatile memory device that is located
inside this specific Model 71.
Model 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
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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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Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Model 77 Device Address, Stereo Input C
Sample Rate Converter, and Post-Fader Stereo Monitor Output
and hold the Mute/Solo button
 Press
to display and select 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 bypassed; LED lit means SRC
enabled. Use the button to change the configuration.
When the Mode
button is pressed,
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.
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 76D.
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Studio Technologies, Inc.
Issue 4, April 2011
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Configuration—Sync Source, Sync Input Termination,
Audio-Synced-to-Video Sample Rate, and Monitor Output Types
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 the Channel Solo C and LFE buttons
to select the pre-fader surround/stereo
input C direct monitor output type.
Use the buttons to change the configuration. C LED lit means AES3id (75 ohms/
1 Vpp); LFE LED lit means AES3 (110
ohms/5 Vpp).
Use the Channel Solo LS and RS
buttons to select the post-fader surround/stereo monitor output type.
Use the buttons to change the configuration. LS LED lit means AES3id
(75 ohms/1 Vpp); RS LED lit means
AES (110 ohms/5 Vpp).

Press and hold
the Stereo to
Mono button
to display and
select the sync
source, sync input termination,
audio-syncedto-video-sample
rate, and monitor output types.
Use these buttons
to select the sync
source.
LED Surround B
lit means sync
input, video;
LED Stereo A lit
means sync input,
DRS;
LED Stereo B lit
means sync input,
word clock;
LED Stereo C
lit means L/R of
currently selected
input.
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.
Pre-fader surround/stereo input C direct monitor output type AES3 (110 ohms/5 Vpp).
Post-fader surround/stereo monitor output type AES3 (110 ohms/5 Vpp).
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Model 76D/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.
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 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
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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 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Configuration—Dim Level, Remote Mute All, Remote Dim,
and Input Delay
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, remote dim, and
input delay.
Default:
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.
–20 dB dim level.
Remote mute all enabled.
Remote dim enabled.
Input delay 0 ms.
Model 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
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for Surround
Configuration—LFE Downmix Mode and Pre-Fader Surround
Monitor Output Mode
These LEDs display the configuration of the pre-fader
surround monitor output mode. LED L lit means
outputs are pre-downmix; LED R lit means outputs
are post-downmix. Use the buttons to change the
configuration.
This LED displays the configuration of the LFE
downmix mode. LED not lit means LFE downmix mode is disabled; LED lit means enabled.
Use the button to change the configuration.

Press and hold
the Surround to
Stereo button to
display and set
the LFE downmix
and pre-fader
surround monitor
output modes.
Default:
LFE downmix disabled.
Pre-fader surround monitor outputs pre-downmix.
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Model 76D/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 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
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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 LFE
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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Model 76D/77 User Guide
Studio Technologies, Inc.
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.
Factory Defaults:
Device address A1.
Stereo input C sample rate converter enabled.
Post-fader stereo monitor outputs can be enabled.
Sync source is L/R of currently selected input.
Sync input terminated.
Audio-synced-to-video sample rate 48 kHz.
Pre-fader surround/stereo input C direct monitor output
type AES3 (110 ohms/5 Vpp).
Post-fader surround/stereo monitor output type AES3
(110 ohms/5 Vpp).
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.
Input delay 0 ms.
LFE downmix disabled.
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.
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.
Model 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
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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 guide may
prove valuable.
Upon 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 76D Central Controller
The Model 76D’s front panel contains two
LEDs. The control console status LED will
light whenever the Model 76D 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 76D. 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
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been connected. Two system functions can
also 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.
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
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
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. Please
refer to the Specifications section of this
guide if you’d like a detailed description of
how the downmix functions perform their
tasks.
A specific downmix function can only be
enabled when it is applicable for the currently selected input source. This means
that the 5.1 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
5.1 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
5.1 to stereo downmix function will again
become active.
5.1 to Stereo
When the 5.1 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 LoRo, is routed
Model 76D/77 User Guide
Studio Technologies, Inc.
to the L and R surround monitor output
channels. The C, LFE, LS, and RS 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 LFE monitor output channels are
muted.
When a surround source has been
selected for monitoring, the 5.1 to stereo
downmix function will automatically enable
whenever the stereo to mono downmix
function is enabled. This ensures that an
operator 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
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
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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 and right 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.
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.
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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!
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
Model 76D/77 User Guide
Studio Technologies, Inc.
for 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),
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
Model 76D/77 User Guide
Studio Technologies, Inc.
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
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.
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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, delay, downmix, and level control
functions.
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 operator
to select between the mute and solo functions. It is also used to select which solo
mode, normal or channel pop, is active.
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-todisable “latching” mode. Multiple channels
can be muted or soloed at the same time.
The LED associated with any muted or
soloed channels is used to indicate that
the function is active.
The mute/solo button is also used to select
the solo mode, the choices being normal
or channel pop. Simply press and hold the
mute/solo button for a few seconds until
the LED associated with the solo mode
lights in the desired manner; steady to
indicate normal solo mode and flashing
for channel pop solo mode. Once the state
of the mode has changed as indicated by
the LED (steady-to-flashing or vice-versa)
the desired solo mode becomes active
and the mute/solo button can be released.
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The selected solo mode will be maintained
even after the system is powered down
and subsequently powered up.
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.
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,
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
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 76D and then configured for 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 76D/77 User Guide
Studio Technologies, Inc.
Model 71 Control Console
The Model 71 Control Console provides
a limited number of pushbutton switches,
LEDs, and a rotary level control for status
display and control. The two buttons, along
with associated LEDs, provide access to
the dim and reference level functions. A
rotary level control allows adjustment of
the post-fader surround and stereo monitor
output levels. 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.
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.
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.
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.
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Technical Notes
48.0, 88.2, 96.0, 176.4, or 192.0—will
momentarily be displayed.
Loss of Sync
Any time that a valid sync signal is not
connected to the Model 76D the 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 76D the
monitor outputs will automatically switch to
their correct sample rate and audio signals
will again be present.
The Model 76D relies on an external timing
reference (sync) source for proper operation. This can be in the form of an AES3id,
word clock, DRS (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 76D’s back panel. Alternately,
a configuration choice allows the L/R input
of the AES3id 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
76D 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.
If a valid sync signal is not present
several visual indications are provided.
On the Model 76D 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 76D’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 76D’s
configuration.
If during normal operation the sync source
changes from one valid rate to another a
visual indication is provided. On the Model
77 units the new sample rate—32.0, 44.1,
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Power Down
Great care was taken in the Model 76D’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 and Error
Codes
Upon mains power being applied to the
Model 76D 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 76D software versions:
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
1. Displays 77
2. Displays Model 77’s software version
3. Displays Model 77’s unit address
(A1, A2, A3, or A4)
4. Displays 76d
5. Displays Model 76D’s main software
version
6. Displays FPgA
7. Displays Model 76D’s logic device
(FPGA) software version
After a successful system power-up
sequence normal operation will then commence. 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 76D. The most likely cause would
be incorrect wiring of the data pair linking
the two units. Err2 indicates that the Model
76D is having problems with its internal
logic device. (A high-speed field-programmable gate array (FPGA) serves as the
digital “heart” of the Model 76D 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
76D 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.
Sample Rate Conversion
(SRC)
Circuitry associated with stereo input C
can provide sample rate conversion (SRC)
Model 76D/77 User Guide
Studio Technologies, Inc.
capability. A digital audio signal connected
to that input can have its sample rate and
timing re-synchronized to match the Model
76D’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 76D. The
technical capabilities of the Model 76D’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 76D’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
76D’s output sample rate is determined
by the selected timing reference (sync)
signal and, if required, a configured value.
If a word clock, DRS (AES11), or AES3id
signal is the designated sync source its
rate will be the Model 76D’s output sample
rate. If a video sync signal is connected,
the Model 76D’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 76D’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 76D’s SRC function to re-synchronize a signal that proves
most valuable. For example, in typical postproduction and broadcast applications all
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signals will have a sample rate of 48 kHz.
A Model 76D 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 76D’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 76D to Control Console
Connections
Figure 7 gives a detailed description of the
signals that connect the Model 76D Central Controller to the one or more Model 77
or Model 71 Control Consoles. The Model
76D provides a +12 volt DC power source
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 76D’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 76D 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.
Issue 4, April 2011
Page 42
“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 76D 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.
Channel Status, User, and
Validity Bits
The non-audio bits that are part of the
AES3/AES3id digital audio monitor output
channel data are actively controlled by the
Model 76D’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 76D’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.
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Specifications
Model 76D 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: one sample (e.g., 0.021
milliseconds @ 48 kHz sample rate)
Digital Audio Inputs: five (18 audio channels)
Configuration: two surround (5.1) and three stereo
Type: AES3id-2001/SMPTE 276M (unbalanced
75 ohms/1 Vpp)
Connectors: BNC (per IEC 60169-8 Amendment 2)
Downmix:
Functions: 5.1 to stereo, stereo to mono
5.1 to Stereo: LS @ –3 dB summed with L;
RS @ –3 dB summed with R;
C @ –6 dB summed with L and R;
LFE @ –6 dB summed with L and R (if enabled);
C, LFE, LS, and RS monitor outputs mute
Stereo to Mono: L @ –3 dB summed with R @
–3 dB to C;
L, R, LS, RS, and LFE monitor outputs mute (for a
surround input this results in the C output being the
sum of L @ –3 dB, R @ –3 dB, C @ –3 dB, LFE @
–3 dB (if enabled), LS @ –6 dB, and RS @ –6 dB)
Control Console Interface:
Type: RS-485, 115.2 kbit/s, 8-1-N
Polling Interval: 50 milliseconds
Power: 12 volts DC, 500 milliamperes maximum
Sample Rate Conversion (SRC):
Application: available on Stereo Input C
Connector: 9-pin D-subminiature female (DE-9F)
Input Sample Rate Range: 8 to 216 kHz, limited
to 1/6 to 6 times the output sample rate
Remote Control Inputs: 2
Functions: remote mute all, remote dim
Latency: 1 millisecond, nominal
Type: +5 V logic, activates on closure to system
common
Sync Source: configured to follow L/R of currently
selected input or signal connected to sync input
Connector: 9-pin D-subminiature female (DE-9F)
Sync Input:
Compatible Sources: word clock, DRS (AES11),
bi-level video, tri-level video
AC Mains:
Requirement: 100 to 230 V, +10/-15%, 50/60 Hz,
15 W maximum
Jitter: 4 ns pp maximum
Connector: 3-blade, IEC 320 C14-compatible
(mates with IEC 320 C13)
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: AES3 (110 ohms/5 Vpp) or AES3id/SMPTE
276M (75 ohms/1 Vpp), selectable
Connector: 25-pin D-subminiature female (DB-25F)
Configurable 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
Model 76D/77 User Guide
Studio Technologies, Inc.
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: 6.2 pounds (2.8 kg)
Model 77 Control Console
Application: up to four Model 77 Control Consoles
can be connected to a Model 76D Central
Controller
Power: 12 volts DC nominal (9 volts DC minimum),
maximum current 100 milliamperes, provided by
Model 76D Central Controller
Issue 4, April 2011
Page 43
for Surround
Control Data:
Type: RS-485
Data Rate/Format: 115.2 kbit/s, 8-N-1
Connector: 9-pin D-subminiature female (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)
Weight: 1.7 pounds (0.8 kg)
Model 71 Control Console
Application: up to three Model 71 Control
Consoles can be connected to a Model 76D
Central Controller
Power: 12 volts DC nominal (9 volts DC minimum),
maximum current 35 milliamperes, provided by
Model 76D Central Controller
Control Data:
Type: RS-485
Data Rate/Format: 115.2 kbit/s, 8-N-1
Connector: 9-pin D-subminiature female (DE-9F)
Dimensions (Overall):
3.20 inches wide (8.1 cm)
2.20 inches high (5.6 cm)
4.10 inches deep (10.4 cm)
Weight: 0.8 pounds (0.4 kg)
Specifications and information contained in this
User Guide subject to change without notice.
Issue 4, April 2011
Page 44
Model 76D/77 User Guide
Studio Technologies, Inc.
for Surround
Appendix A—Connection Pin-Out
Charts
Connections
TASCAM® Signal
Channel High (+)
Signal
Low (–)
Shield
Signal
Pin
Direction
Data + (RS-485/RS-422)
7
Not used
Data – (RS-485/RS-422)
2
Not used
Data Shield
1
Shield
Pre-Fader L/R
1
24
12
25
Pre-Fader C/LFE
2
10
23
11
Pre-Fader LS/RS
3
21
9
22
Stereo Input C Direct
4
7
20
8
Remote Mute All
5
Input
Post-Fader L/R
5
18
6
19
Remote Dim
6
Input
Post-Fader C/LFE
6
4
17
5
Remote Spare 1
8
Input
Post-Fader LS/RS
7
15
3
16
Remote Spare 2
9
Input
Post-Fader Stereo
8
1
14
2
Remote Input Common
4
Common
Notes: 1) All signals transformer-coupled digital audio;
selectable for AES3 or AES3id compatibility.
2) Connector type on Model 76D is 25-pin
D-subminiature female (DB-25F). Installer must
provide male (DB-25M). Connector uses 4-40
threaded inserts for locking with mating plug.
Note: Connector type on Model 76D is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Connections for Remote Control Inputs
3) Wiring scheme follows TASCAM D-88 convention.
Standard D-88-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Connections for Digital Monitor Outputs
Signal
Pin
Direction
Data + (RS-485)
1
To/From Models 77/71
Data – (RS-485)
6
To/From Models 77/71
Data Shield
2
To/From Models 77/71
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 76D is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Connections between Model 76D and
Model 77 and Model 71
Model 76D/77 User Guide
Studio Technologies, Inc.
Issue 4, April 2011
Page 45
for Surround
Appendix B—Sync Input Sources
The Model 76D’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.
DRS (AES11) or AES3id: 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
Issue 4, April 2011
Page 46
Model 76D/77 User Guide
Studio Technologies, Inc.
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