Studio Technologies 76DA, 77 User's Guide
for Surround
Model 76DA Central Controller and
Model 77 Control Console
User Guide
Issue 2, April 2011
This User Guide is applicable for systems consisting of:
Model 76DA: serial number M76DA-00151 and later with software version
Model 77: serial number M77-00265 and later with software version 3.01 and higher
3.01 and higher;
© 2011 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50241-0411, Issue 2
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for Surround
Table of Contents
Introduction ................................................................... 5
Installation .................................................................... 8
Configuration ................................................................16
Operation ......................................................................34
Technical Notes ............................................................40
Specifications ...............................................................44
Appendix A—Connection Pin-Out Charts ....................46
Appendix B—Sync Input Sources ................................47
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Issue 2, April 2011 Model 76DA/77 User Guide
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Introduction
What This User Guide Covers
This User Guide is designed to assist you
when installing and using the Model 76DA
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 76DA
Central Controller and the Model 77 and
Model 71 Control Consoles. With digital
audio inputs, digital and analog 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 multiformat 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, allowing
fingertip selection of all monitoring functions. Numerous LED indicators provide
complete status information. A 4-digit
numeric display indicates the post-fader
monitor output level in real time. A major
strength of the Model 77 is its ability to
configure, under software control, many
important operating parameters. Intended
for secondary monitoring locations, the
Model 71 Control Console is a compact
user control surface. It provides three of
the most basic functions: a rotary level
control, dim on/off button, and reference
level on/off button.
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 76DA provides
power for all connected Model 77 or Model
71 units.
The core of this StudioComm for
Surround system is the Model 76DA
Central Controller. The one-rack-space
unit contains digital audio input, digital
and analog monitor output, processing,
and support circuitry. The Model 76DA
provides two surround (5.1) and three
stereo digital audio inputs. These unbalanced digital inputs are AES3id/SMPTE
276M-compliant; 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 76DA’s digital audio timing reference. For synchronization with a master
timing reference a dedicated source of
word clock, DARS (AES11), bi-level video,
or tri-level video can be connected. Alternately, the L/R connection of the actively
selected surround or stereo input source
can serve as the timing reference.
A range of digital and analog surround
(5.1) and stereo monitor outputs are provided. The post-fader surround and stereo
digital and analog monitor outputs are
intended for connection to monitor loudspeaker systems. The pre-fader surround
digital 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 digital monitor output allows an
installation to directly access the SRC
capabilities.
For installation flexibility the digital 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-topeak (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-program
-
mable gate array (FPGA) integrated circuit.
The Model 76DA occupies one space (1U)
in a standard 19-inch rack. Digital audio
sources are interfaced with the Model 76DA
using nine BNC connectors. A tenth BNC
connector is used by the sync source.
Digital and analog monitor output signal
connections are made using two 25-pin
D-subminiature connectors. One 9-pin
Figure 1. Model 76DA Central Controller Front Panel
Figure 2. Model 76DA Central Controller Back Panel
AC mains input
Remote control
inputs
To/from
Models 77 &
71 Control
Consoles
monitor outputs
Digital
monitor
outputs
Analog
Sync
Input
Stereo
Input C
Surround Input B
Control console
status LED
Surround Input A
Sync status
LED
Stereo Input A and
Stereo Input B
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Mute/solo
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Channel mute/solo
Downmix
Input source
select
Figure 3. Model 77 Control Console Front Panel
D-subminiature connector is used to connect the Model 76DA 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 76DA, 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 digital
and analog monitor output levels can be
controlled by way of a large, easy-to-use
rotary control. The control, actually a digital
encoder, allows level selection in precise
Monitor output
level display
Post-fader surround
monitor output
• Surround/stereo
• Reference level
• Mute all
• Dim
• Rotary level control
0.5-dB steps. The auto mute all function
causes the post-fader surround and stereo
digital and analog 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 digital and
analog 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 digital and analog 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 digital and analog monitor output levels to be reduced by a fixed
dB amount. The dim level is configured
from among four available values. A mute
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all function allows 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
digital and analog monitor outputs. A configuration setting allows the pre-fader surround digital monitor output to be selected
for pre- or post-downmix operation.
For flexibility, the StudioComm for Surround
system is designed to easily integrate with
equipment such as production intercom
systems, on-air or recording tally signals,
and audio consoles. Two remote-control
inputs provide access to the mute all and
dim functions. By providing access to these
functions, talkback or slate activity from
an audio console or other communications
system can control the level of the postfader surround and stereo digital and
analog monitor outputs.
Installation
In this section you will be installing the
Model 76DA Central Controller in an equipment rack. Connections to the digital audio
inputs and digital and analog 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 76DA. AC mains power
will be connected to the Model 76DA. For
advanced applications up to three additional
Model 77 or Model 71 Control Console units
can be connected to the Model 76DA.
System Components
The main shipping carton contains one
each of the following: Model 76DA 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 76DA
The Model 76DA Central Controller
requires one space (1U) in a standard
19-inch (48.3 cm) equipment rack. Secure
the Model 76DA 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 76DA 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 two 25-pin D-subminiature connectors. All the connectors are
located on the Model 76DA’s back panel.
Refer to Figure 2 for a detailed view of
these jacks and the connector.
Digital 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
digital and analog 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 digital monitor
output.
The digital audio inputs support digital
audio signals with a sampling rate of up to
192 kHz and a word length (depth) of up
to 24 bits. It’s best if the connected signal
sources maintain a common sample rate
and timing reference. Having all signals
“locked” together helps to ensure proper
handling by the Model 76DA’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 76DA’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 76DA’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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Digital Monitor Outputs
The 25-pin D-subminiature connector
labeled Digital Monitor Outputs provides
access to the Model 76DA’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 digital monitor output
channels are intended for connection to
metering or monitoring equipment that
requires uninterrupted full-level signals.
The post-fader surround digital monitor
output channels are intended to connect to
a 5.1 loudspeaker system. The post-fader
stereo digital monitor output is provided to
support a separate set of stereo monitor
loudspeakers.
The stereo input C direct digital 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 76DA’s configuration settings.
For flexibility the digital monitor outputs
are transformer-coupled and can be configured to act as AES3 or AES3id digital
audio sources. The digital 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/post-fader 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 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 digital 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
76DA’s digital monitor outputs, when
configured for AES3 (110 ohms/5 Vpp),
would be identical to that of a DA-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
76DA’s digital 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.
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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 DA-88-style assembly, the two threaded
fasteners associated with the Model 76DA’s
D-sub connectors use 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
TASCAM® Signal Signal
Connections Channel High (+) Low (–) 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
Post-Fader L/R 5 18 6 19
Post-Fader C/LFE 6 4 17 5
Post-Fader LS/RS 7 15 3 16
Post-Fader
Notes: 1) All signals transformer-coupled digital audio;
selectable for AES3 or AES3id compatibility.
2) Connector type on Model 76DA 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 DA-88 convention.
Standard DA-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
Stereo 8 1 14 2
Pre-Fader Surround Digital Monitor
Output
The pre-fader surround digital 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 Digital Monitor
Output
The stereo input C direct digital 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 Digital Monitor
Output
The post-fader surround digital 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 Digital Monitor
Output
The post-fader stereo digital 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.
Analog Monitor Outputs
The connector labeled Analog Monitor
Outputs provides access to the Model
76DA’s 6-channel (5.1) surround and
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2-channel stereo analog monitor outputs.
The surround analog monitor output channels are intended to connect to analog
inputs associated with the surround loudspeaker system incorporated in a facility.
The stereo analog monitor output allows
support for a secondary set of stereo monitor loudspeakers.
The analog monitor output channels are
designed for connection to audio amplifiers
associated with monitor loudspeakers or
to the inputs of loudspeakers that contain
integrated amplifiers. The analog monitor
outputs are electronically balanced and will
perform optimally when driving loads of
2000 (2 k) ohms or greater. In most applications 3-pin XLR plugs (male) will be used
to interface with the inputs on the associated amplifiers or amplified speakers. 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.
Balanced operation of the analog monitor
outputs is the preferred connection method
but unbalanced operation does not pose a
problem. To connect to an unbalanced load
connect the + terminal as signal high, and
only the Model 76DA’s shield terminal as
the signal low/shield. Leave the – terminal
unconnected. For correct unbalanced
operation, it is important not to connect
– and shield together.
The wiring scheme used by the D-subminiature connector complies with that made
popular by TASCAM® with their DA-88®
product. A wiring assembly prepared for
the Model 76DA’s analog monitor outputs
is identical to that of a DA-88-style output
assembly. Please refer to Figure 5 for the
exact connection details. Again note that
unlike a DA-88-style assembly, the Model
76DA’s D-sub connectors use 4-40 threads.
Signal Signal
Connections High (+) Low (–) Shield
Surround L 24 12 25
Surround R 10 23 11
Surround C 21 9 22
Surround LFE 7 20 8
Surround LS 18 6 19
Surround RS 4 17 5
Stereo L 15 3 16
Stereo R 1 14 2
Notes: 1) Connector type on Model 76DA is 25-pin
D-subminiature female
male
for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-type wiring harnesses are directly
compatible, with the exception of 4-40 screw threads
being required.
Figure 5. Connections for Analog Monitor
Outputs
(DB-25M). Connector uses 4-40 threaded inserts
(DB-25F). Installer must provide
Sync Input
The Model 76DA requires a timing reference (sync) signal so that the digital audio
input and monitor output signals will be
handled correctly. A configuration setting
allows the source of sync to be the L/R
input of the currently selected surround
or stereo digital audio input. While this is
acceptable, audio artifacts (clicks or noise)
can occur when switching between inputs.
A better method is to connect a dedicated timing reference signal to the Model
76DA’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,
DARS (AES11), bi-level video, or tri-level
video.
An overview of the various compatible
timing reference signals might prove
worthwhile. Word clock is a digital signal
that is locked in phase and frequency to
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the sample rate of the associated digital
audio sources. DARS (digital audio reference source) is a timing signal compliant
with the AES11 standard. It’s sometimes
referred to as “AES3-black.” Technically it
is similar to an AES3 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 76DA 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 76DA’s back panel.
For flexibility this input can be configured
to be high-impedance (“floating”) or terminated with an impedance of 75 ohms.
A sync source that is dedicated for use by
the Model 76DA’s sync input will typically
have input termination enabled. If the sync
signal connected to the Model 76DA 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 digital
and analog monitor outputs. The Model
76DA’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 overcurrent and static discharge (ESD), care
should be taken to prevent nasty signals
from reaching them. The inputs are active
only when held in the low state; they can’t
be configured to change state (“latch”) in
response to a logic pulse.
A 9-pin D-subminiature connector is used
for the remote control inputs. Refer to
Figure 6 or Appendix A for the exact connection details. Note that pin 4 (remote
common) connects to the Model 76DA’s
internal circuit common connection as well
as to the Model 76DA’s chassis and mains
earth connections. Figure 6 also shows
two spare remote control inputs (pins 8
Signal Pin Direction
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 In
Remote Spare 2 9 Input
Remote Common 4 Common
Note: Connector type on Model 76DA is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Figure 6. Connections for Remote Control
Inputs
put
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and 9). These are provided for future applications and should remain unconnected.
This connector also allows access to an
RS-485 data interface. This interface is
not supported in the Model 76DA and,
as such, pins 7 and 2 should remain
unterminated.
Connecting the Model 76DA
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 76DA
Central Controller. This is used to interface
the unit with Model 77 Control Consoles.
Refer to Figure 7 or Appendix A for details.
A 9-pin female D-sub connector, labeled
To/From Central Controller, is provided on
the back panel of each Model 77 Control
Console. A cable with 9-pin male D-sub
(DE-9M) connectors on each end is used
to interconnect the Model 76DA 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 can be wired in a one-to-one fashion
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 76DA is 9-pin D-subminiature
female (DE-9F). Connector uses 4-40 threaded inserts
for locking with mating plug.
Figure 7. Connections between Model 76DA and
Model 77 and Model 71
supporting all nine pins, only four
connections are required: pin 1 (data +),
pin 6 (data –), pin 4 (DC +), and pin 9
(DC –). The Model 76DA’s connector pinout 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.
A few simple calculations are required to
determine the maximum cable length when
connecting a Model 76DA 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
76DA to a Model 77. The Model 76DA supplies 12 volt DC with a maximum current of
500 milliamperes.
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
76DA 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
Issue 2, April 2011 Model 76DA/77 User Guide
Page 14 Studio Technologies, Inc.
for Surround
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 76DA’s ability to be controlled by additional control consoles. At least one Model
77 Control Console must be connected to
the Model 76DA 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 76DA.
When connecting multiple control consoles
to a Model 76DA 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 –).
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.
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 76DA operates directly from
AC mains power of 100 to 230 V, 50/60 Hz.
Being a “universal input” device, there are
no switches to set or jumpers to install to
match a location’s mains voltage. The unit
uses a 3-pin IEC 320 C14-type inlet connector to mate with a detachable mains
cord. All units are supplied with a mains
cord that has a North-American standard
plug (NEMA 5-15L) on one end and an
IEC 320 C13 socket on the other. Units
bound for other destinations require that
the appropriate cord be used. The wire
colors in the mains cord must conform to
the internationally recognized color code
and should be terminated accordingly:
Connection Wire Color
Neutral (N) Light Blue
Line (L) Brown
Protective Earth (E) Green/Yellow
Safety Warning: The Model 76DA
does not contain an AC mains dis
connect 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.
-
Refer to the previous paragraphs of this
user guide where the issues involving
Model 76DA to Model 77 cable length are
Model 76DA/77 User Guide Issue 2, April 2011
Studio Technologies, Inc. Page 15
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