Studio Technologies 76B User Manual
for Surround
Model 76B Central Controller and
Model 77B Control Console
User Guide
Issue 1, July 2008
This User Guide is applicable for systems consisting of:
Model 76B: serial number M76B-00151 and later with software version 1.03;
Model 77B: M77B-00151 and later with software version 1.02
© 2008 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50228-0708, Issue 1
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for Surround
Table of Contents
Introduction ................................................................... 5
Installation .................................................................... 8
Advanced Installation ...................................................14
Confi guration ................................................................15
Operation ...................................................................... 31
Technical Notes ............................................................37
Specifi cations ...............................................................40
Block Diagrams
Model 76B Central Controller
Model 77B Control Console
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Issue 1, July 2008 Model 76B/77B 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 76B
Central Controller and one or more associated Model 77B Control Consoles.
Overview
As creating and distributing multi-channel
surround (5.1) and stereo (2-channel) audio
material has become a day-to-day reality,
the ability to simply and effectively monitor
these sources is imperative for recording,
post-production, and broadcast facilities.
Studio Technologies has addressed these
needs with the StudioComm for Surround
Model 76B Central Controller and Model
77B Control Console. With its digital audio
inputs, analog outputs, Dolby® E dialnorm
support, and extensive set of user resources it’s a simple task to integrate the system
into virtually any facility. The carefully
selected group of features, including
fl exible input source selection, dialnorm
display, channel downmix, channel solo,
and reference level, 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.
With the StudioComm for Surround system
any audio console, disk-based recording
system, or broadcast facility can have a
complete multi-channel monitor system. Its
unique feature set makes it especially well
suited to meet the unique needs of broadcast master control applications.
A StudioComm for Surround system
starts with the Model 76B Central Controller. It occupies one space in a standard
19-inch rack. Two surround (5.1) and three
stereo (2-channel) audio inputs, along with
a surround (5.1) and an auxiliary stereo
(2-channel) monitor outputs, are provided.
The surround and stereo inputs are digital and compatible with AES3id sources.
These unbalanced digital signals utilize
BNC connectors and are ubiquitous in most
post-production and broadcast environments. Sample rates of up to 192 kHz and
bit depth of up to 24 are directly supported.
With the system’s dynamic range of greater
than 106 dB, there isn’t a problem ensuring
that a source’s audio quality is maintained.
The monitor outputs are analog, balanced
line-level, with a maximum signal level of
+26 dBu. They include power-up/powerdown protection circuitry to help maintain
the health of the connected loudspeaker
systems.
A source of Dolby E metadata can be
connected to the Model 76B Central Controller. This RS-485/RS-422 115.2 kbit/s
serial data signal carries numerous data
elements, including one that represents
the average dialog level of an associated
audio program. This dialog normalization
or “dialnorm” value is an integral part of
many broadcast distribution systems, ending up as part of consumer audio playback
systems. Hardware and software within the
Model 76B separates the dialnorm element
that relates to one of the connected surround audio sources. This dialnorm level
value can be displayed on the Model 77B
Control Console, as well as being used to
automatically adjust the surround monitor
output level. This provides a unique solution
to the broadcast and post-production world,
allowing a professional environment to accurately simulate an end user’s experience.
Digital audio signals are interfaced with the
Model 76B using nine BNC connectors.
Analog monitor output signal connections
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are made using one 25-pin D-subminiature
connector. An advanced flash-based
microcontroller integrated circuit provides
the logic “horsepower” for the unit. AC
mains power is connected directly to the
Model 76B, which is factory selected for
100, 120, or 220/240 V operation. The
internal power supply utilizes two toroidal
mains transformers for quiet audio operation. One 9-pin D-subminiature connector
is used to connect the Model 76B with up
to four Model 77B Control Consoles. A
second 9-pin “D-sub” connector is used to
interface the Dolby E dialnorm data and
remote control signals with the Model 76B.
The Model 77B Control Console is the
“command center” and is designed to
reside at an operator’s location. It allows
fi ngertip selection of all monitoring functions. Numerous LED indicators provide
complete status information. A 4-digit
numeric display indicates the monitor output or dialnorm level in real time. A major
strength of the Model 77B is its ability to
confi gure, under software control, many
important operating parameters.
While most installations will use only one
Model 77B Control Console, up to four
can be connected to a Model 76B Central
Controller. This provides multiple users
with full control over a facilities’ monitor
system. The Model 76B can provide power
for the fi rst two Model 77B units while an
external 12 volt DC source is required for
a third and fourth unit. The interconnecting
cables use 9-pin D-subminiature connectors to carry RS-485 data and DC power.
Additional Details
The Model 77B provides four buttons and
associated LEDs for selecting the input
source to be monitored. The buttons are
designed such that up to six unique input
choices are available. Using the Model
77B’s confi guration mode, each of the six
input choices can be confi gured from the
Figure 1. Model 76B Central Controller Front Panel
Control console
to/from data
active LED
Figure 2. Model 76B Central Controller Back Panel
AC mains
input connection
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To/from
Model 77B
Control
Console
RS-485 and
remote control
inputs
Analog monitor
output connections
Stereo Input C
connection
Surround Input B
connections
Surround Input A
connections
Metadata
active
LED
Stereo Input A and
Stereo Input B
connections
Powe r
present
LED
Director cue
output enable
for Surround
Channel solo
Downmix
Input select
Figure 3. Model 77B Control Console Front Panel
system’s two surround (5.1) and three
stereo (2-channel) inputs. The confi guration mode also allows stereo inputs A and
B to be used as either stereo or monaural sources. This is especially useful in
broadcast applications where a 2-channel
AES3id source may carry two independent
monaural signals. To highlight this powerful
feature: the Model 77B allows independent
monitoring of the two channels associated
with a single AES3id source. Broadcast
master control applications can greatly
benefi t from this confi guration fl exibility.
The surround monitor output level can be
controlled by way of a large, easy-to-use
rotary control. The control, actually a digital
encoder, allows level selection in precise
0.5-dB steps. The auto mute all function
causes the monitor output channels to
automatically mute whenever the output
level is set to its minimum position. Using
the reference level function, the monitor
output level can be set to a pre-confi gured
value. This is provided for audio-withpicture applications that require a specifi c
Display mode
Dialnorm and
monitor output
level display
Monitor Output
• Dialnorm enable
• Reference level
• Mute all
• Dim
• Rotary level control
monitor output level. The reference level
is easily confi gured by taking an electronic “snapshot” of the desired monitor
output level. For operator confi rmation a
4-digit LED readout can display the level
of the surround monitor output channels.
To match the needs of a facility, it can be
confi gured to display either the attenuation
level or the sound pressure level (SPL).
The dim function allows the surround
monitor output level to be reduced by a
fi xed dB amount. The dim level is confi gured from among four available values. A
mute all function allows all surround monitor output channels to be simultaneously
muted. The channel solo section provides
individual surround channel monitoring
control, allowing a single channel to be
monitored while the others are automatically muted. Multiple channels can also
be simultaneously selected for “soloing.”
A special solo mode is also provided,
called channel pop solo, which offers a
unique aid in monitoring audio material.
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Channel pop solo allows the level of a
single channel to be raised while the level
of the other channel is reduced. This helps
to emphasize the content on one channel
without fully muting the others. Broadcast
applications can benefi t from the channel
pop solo mode, 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 confi gured to meet the needs
of specifi c 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.
In addition to the surround (5.1) monitor
output, a stereo (2-channel) auxiliary monitor output is also provided. A stereo signal,
connected to stereo input C on the Model
76B Central Controller, can be routed to
the auxiliary output. A pushbutton on the
Model 77B Control Console allows on/off
control of the signal; no level control or
signal modifi cation takes place. The auxiliary output feature can be useful in special
applications, e.g., in a broadcast control
room setting where an audio signal, such
as site-event cue signals, needs to be
monitored by way of an independent set of
loudspeakers.
For fl exibility, the StudioComm for
Surround system is designed to easily
integrate with equipment such as production intercom systems, on-air or recording
tally signals, audio consoles, and fi lm
motion-control electronics. Three remotecontrol input functions are provided: mute
all, dim, and auxiliary output on/off. By providing access to these functions, talkback
or slate activity from an audio console or
other communications system can control
the level of the surround monitor output or
enable to the auxiliary output.
Installation
In this section you will be installing the
Model 76B Central Controller in an equipment rack. Connections to the digital audio
inputs and analog monitor outputs will
be made. If desired, a source of Dolby E
metadata will be connected and external
equipment will be interfaced to the remote
control inputs. A location will be selected
for the fi rst Model 77B Control Console
and it will be connected to the Model 76B.
AC mains power will be connected to the
Model 76B.
For advanced applications up to three
additional Model 77B Control Console
units can be connected to the Model 76B.
Please refer to the Advanced Installation
section of this guide for details.
System Components
The main shipping carton contains one
each of the following: Model 76B Central
Controller, Model 77B Control Console,
20-foot (6.1-meter) 9-pin D-sub interconnecting cable, and user guide. Units destined for North America also include an
AC mains cord. Your dealer or distributor
Issue 1, July 2008 Model 76B/77B User Guide
Page 8 Studio Technologies, Inc.
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should provide an AC mains cord for destinations outside of North America. Any
additional Model 77B Control Consoles
will be shipped in separate cartons.
Mounting the Model 76B
The Model 76B Central Controller requires
one space in a standard 19-inch (48.3 cm)
equipment rack. Select a location that is
convenient for making connections to the
digital and analog audio signals as well
as interfacing with the Model 77B Control
Console. A 20-foot (6.1-meter) cable is
supplied to connect the Model 76B to the
Model 77B. If the needs of a specifi c installation dictate, an alternate-length interconnecting cable can be fabricated and used.
Secure the Model 76B into the equipment
rack using two mounting screws per side.
Audio Connections
Audio signal connections are made by
way of nine BNC jacks and one 25-pin
D-subminiature connector which are located on the Model 76B’s back panel. Refer
to Figure 2 for a detailed view of the back
panel. The BNC jacks will be used for interconnecting with the digital audio signals. A
cable assembly with a 25-pin D-sub plug
(male) on one end and the desired connectors on the other end will be used for
connecting to the analog monitor outputs.
Digital Audio Inputs
Prior to sources being connected to the
fi ve inputs it’s worth reviewing how they
are used by the StudioComm system.
Surround inputs A and B each have six
channels (5.1) and can be confi gured
for monitoring over the surround monitor
output channels. The relationship between
input channels and output channels is
maintained, 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 special
case where the 5.1 to stereo downmix
function is enabled.)
Stereo inputs A and B can be confi gured
to be used as a stereo source or as two
independent monaural sources. When
confi gured as a stereo source the left
channel is routed to the left monitor output
and the right channel to the right monitor
output. Alternately, the left and right input
channels can be independently confi gured
to output by way of the monitor output’s
center channel. In this way a single digital
audio source can supply one or two monaural signals to the StudioComm system
and be correctly monitored.
Stereo input C is unique in that it can serve
as a source for both the surround and the
auxiliary monitor outputs. As with the other
inputs, stereo input C can be assigned,
using the confi guration function, to an input
select button. This will allow stereo input
C to be monitored using the left and right
channels of the surround monitor output. In
addition, the signal connected to stereo input C will be routed to the auxiliary output
whenever that function is active. To clarify:
if the auxiliary output is enabled (turned
on) a signal on the left channel of stereo
input C will be present on the left channel
of the auxiliary output; a signal on the right
channel of stereo input C will be present
on the auxiliary output’s right channel.
It’s important to note that there is one
limitation regarding stereo input C. Unlike
stereo inputs A and B, it can only be
used as a stereo (2-channel) source. Its
left and right channels can’t be independently monitored over the center channel
of the surround monitor output. (The
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confi guration function doesn’t allow this
anyway so there is no potential for a
problem to develop.) Also, the left and
right channels of stereo input C can’t be
independently monitored by way of the
auxiliary output. It follows a left-in-to-leftout, right-in-to-right-out scheme.
The nine female BNC connectors on the
Model 76B’s back panel are used to interface with digital audio signal sources. Each
of the digital audio inputs is intended for
connection to an unbalanced digital audio
source that is compatible with the AES3id2001 standard. In broadcast environments
these signals may also be referred to as
following the SMPTE 276BM standard.
As expected, these signal sources will
be provided in the form of coaxial cables
with BNC plugs attached. The Model 76B
supports sampling rates of up to 192 kHz
with a word length (depth) of up to 24 bits.
Note that no master external synchronization source is required as each input is
independently self-clocking.
Balanced AES3 digital audio signals
can also be used with the Model 76B’s
inputs if external coupling transformers
(“baluns”) are utilized. These impedancematching (110 ohms to 75 ohms) transformer assemblies typically provide a 3-pin
female XLR connector on their input and
a female BNC connector on their output.
Analog Monitor Outputs
The connector labeled Analog Monitor
Outputs provides access to the Model
76B’s surround (5.1) and stereo (2-channel) auxiliary monitor outputs. The surround output channels are intended to
connect to the main loudspeaker system
incorporated in a facility. The auxiliary
output channels are provided to support a
separate set of loudspeakers, the primary
application intended to allow monitoring of
inter- or intra-facility communications.
The monitor output channels are designed
for connection to audio amplifi ers associated with monitor loudspeakers, or to the
inputs of loudspeakers that contain integrated amplifi ers. The monitor outputs are
electronically balanced and capable of
driving balanced or unbalanced loads
of 600 ohms or greater. While balanced
operation is preferred, unbalanced operation does not pose a problem. To connect
to an unbalanced load connect the
+ terminal as signal high, and both the
– and shield as the signal low/shield. For
optimal unbalanced operation, it is important to connect both – and shield together
directly on the D-sub plug, not at the other
end of the harness.
Note that while the Model 76B’s electronically balanced output circuits are capable
of driving loads of 600 ohms or greater
their output level will drop slightly as the
load impedance approaches 600 ohms.
A 0.5 dB difference in output level can be
expected as the load impedance changes
from 10 k ohms to 600 ohms.
The wiring scheme used by the D-subminiature connector complies with that
made popular by TASCAM® with their
DA-88® product. A wiring assembly prepared for the Model 76B’s monitor outputs
is identical to that of a DA-88-style output
assembly. Please refer to Figure 4 for the
exact connection details. Note that unlike
a DA-88-style assembly, the two threaded
fasteners associated with the Model 76B’s
D-sub connector uses 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
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Signal Signal
Connections High (+) Low (–) Shield
L 24 12 25
R 10 23 11
C 21 9 22
LFE 7 20 8
LS 18 6 19
RS 4 17 5
Auxiliary L 15 3 16
Auxiliary R 1 14 2
Notes: 1) Connector type on Model 76B is 25-pin D-subminiature
female. Installer must provide plug (male). Connector uses
4-40 threaded inserts for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-type wiring harnesses are directly
compatible, with the exception of 4-40 screw threads
being required.
Figure 4. Connections for Surround and
Auxiliary Monitor Outputs
Metadata Input
The Model 76B allows a source of Dolby E
metadata to be directly connected. Hardware and software inside the Model 76B
extracts (“parses”) one of the dialnorm
data elements from the connected metadata signal. This dialnorm value can be
viewed on the Model 77B’s LED display
and, if desired, used to control the monitor
output levels. Refer to the Technical Notes
section of this guide for details.
The metadata signal is connected by
way of a 9-pin D-subminiature connector,
labeled RS-485/Remote Control Inputs,
which is located on the back panel of the
Model 76B. Refer to Figure 5 for exact
connection details. While only the data+
and data– connections are absolutely
necessary, a shield connection can also
be made. Note that the connections for
the metadata signal are reminiscent of
the SMPTE 207M standard.
Signal Pin Direction
RS-485 Data+ 7 Input
RS-485 Data– 2 Input
Data Shield 1 Shield
Remote Mute All 5 Input
Remote Dim 6 Input
Remote Auxiliary Output On/Off 8 Input
Remote Spare 9 Input
Remote Input Common 4 Common
Note: Connector type on Model 76B is 9-pin D-subminiature
female. Connector uses 4-40 threaded inserts for
locking with mating plug.
Figure 5. Connector Pin Outs for Metadata and
Remote Control Inputs
The metadata signal must be in the form
of RS-485 or RS-422 asynchronous serial
data. This differential signal must have a
data rate of 115.2 kbit/s and a data format
of 8 data bits, no parity, and 1 stop bit
(8-N-1). A metadata signal of this type
is commonly available on metadatagenerating or de-embedding equipment
from broadcast equipment manufacturers
such as Dolby Laboratories®, Evertz®,
and NVISION®.
While in hardware the Model 76B’s RS-485
input connection is bi-directional, in software it’s confi gured only to receive data.
This means that there’s no reason why
a signal already connected between two
other pieces of equipment can’t also be
connected in parallel (“bridged”) with the
Model 76B’s metadata input.
A word of advice—Studio Technologies
has found documentation supplied with
some metadata-generating equipment has
incorrect (or at least confusing) pin-out
information. This has resulted in much
head scratching and hair pulling. As such,
it may be valuable to use a logic analyzer
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or oscilloscope to confi rm that the metadata source is actually on the expected pins
of the source connector prior to connecting
it to the Model 76B.
Remote Control Inputs
Support is provided for three remote
control input functions: remote mute all,
remote dim, and remote auxiliary output on/off. The 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 (ESD) discharge, care should be taken to prevent
nasty signals from reaching them. The
inputs are active only when held in the low
state; they can’t be confi gured to change
state (“latch”) in response to a logic pulse.
The same 9-pin D-subminiature connector
used for the metadata input is also used
for the remote control inputs. Refer to
Figure 5 for the exact connection details.
Note that pin 4 (remote input common)
connects to the Model 76B’s internal circuit
common connection as well as the Model
76B’s chassis and mains earth connections. Figure 5 also shows one spare
remote control input (pin 9). This is provided for future applications and should
remain unconnected.
Connecting the Model 76B
to the Model 77B
A 9-pin female D-subminiature connector,
labeled To/From Control Console, is provided on the back panel of the Model 76B
Central Controller. This is used to interface
the unit with Model 77B Control Consoles.
A 9-pin female D-sub connector, labeled
To/From Central Controller, is provided
on the back panel of each Model 77B
Control Console. A cable with 9-pin male
D-sub connectors on each end is used to
interconnect the Model 76B with the Model
77B units. A 20-foot (6.1-meter) 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 covering all nine pins, a minimum of only four
connections are required: pin 1 (data+),
pin 6 (data–), pin 4 (DC+), and pin 9
(DC–). The Model 76B’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,
fl exible, 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. Refer to Figure 6 for details.
A few simple calculations are required to
determine the maximum cable length when
connecting a Model 77B to a Model 76B.
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
76B to the Model 77B. The Model 76B supplies 12 volt DC nominal with a maximum
current of 200 milliamperes.
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Signal Pin Direction
Data+ 1 To/From Model 77B
Data– 6 To/From Model 77B
Data Shield 2 To/From Model 77B
DC+ 4 To Model 77B
DC– 9 To Model 77B
DC Power Shield 5 To/From Model 77B
Note: Connector type on Model 76B is 9-pin D-subminiature
female. Connector uses 4-40 threaded inserts for
locking with mating plug.
Figure 6. Connections between Model 76B and
Model 77B
The Model 77B requires a minimum of
9 volts DC, 100 milliamperes maximum
for correct operation. (The voltage must be
measured directly at the Model 77B’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 76B supplies 12 volts and the Model
77B 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 0.01
(the square of the Model 77B’s maximum
required current). Remember to include
the resistance in both the DC+ and DC–
wires in the fi gure for the total resistance.
our friends “down under” and in Europe
receive units set for 220/240 volts. Before
connecting the Model 76B to AC mains
power, check to be certain that it is confi gured to match the local mains voltage.
Look on the back panel (adjacent to the
power entry connector) for an indication
of the factory-confi gured voltage. Note
that an incorrect confi guration could prevent operation or cause damage to the
unit. Should it be necessary to change
the unit’s operating voltage it must be
performed only at the factory, or by a
factory-authorized service technician.
The Model 76B uses an IEC-standard C14
inlet connector to mate with the AC mains
cord. The AC mains cord should have a
C13 socket affi xed with the wire colors
conforming to the internationally recognized CEE color code:
Connection Wire Color
Neutral (N) Light Blue
Line (L) Brown
Protective Earth (E) Green/Yellow
Safety Warning: The Model 76B does
not contain an AC mains disconnect
switch. As such, 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.
AC Mains Power
The Model 76B is internally confi gured
to operate from nominal 100, 120, or
220/240 volts, 50/60 Hz. Units shipped
to North America are factory selected for
120 volt operation. Units bound for Japan
are generally selected for 100 volts while
Model 76B/77B User Guide Issue 1, July 2008
Studio Technologies, Inc. Page 13
As soon as AC mains power is applied,
the Model 76B Central Controller’s power
LED will light steadily. The two data activity
LEDs, control console and metadata, may
also light. Each of the connected Model
77B Control Consoles will go through a
power-up sequence, lighting each LED in
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