Studio Technologies 78 User manual

50093-0104, Issue 5
© 2004 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
Model 78 Central Controller and
Model 79 Control Console
User Guide
Issue 5, January 2004
This User Guide is applicable for systems consisting of:
Model 78: serial number M78-00151 and later;
Model 79: M79-00151 and later
for Surround
THX® pm3
approved

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Table of Contents
Introduction................................................................... 5
Installation .................................................................... 9
Configuration ................................................................13
Operation......................................................................27
Technical Notes ............................................................31
Specifications ...............................................................38
Appendix A ...................................................................39
MIDI Messages ........................................................40
Block Diagrams
Model 78 Central Controller
Model 79 Control Console

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Model 78/79 User Guide Issue 5, January 2004
Studio Technologies, Inc. Page 5
for Surround
Introduction
What This User Guide Covers
This User Guide is designed to assist you
when installing and using the Model 78
Central Controller and the Model 79
Control Console.
StudioComm for Surround
Once exclusively the domain of major mo-
tion picture studios and large production
facilities, the recording, mixing, editing,
and distribution of multichannel “surround”
audio material has become much more
prevalent. To handle these tasks, the ability
to effectively monitor multichannel sources
has become imperative for more and more
facilities. Studio Technologies has ad-
dressed this need with the StudioComm for
Surround Model 78 Central Controller and
Model 79 Control Console. The system is
perfect for 8-channel “7.1” applications,
including adding 7.1 monitoring capabil-
ity to disk-based recording systems. It’s
also ideal for upgrading a post-production,
mastering, or broadcast facility to support
multichannel monitoring. The StudioComm
for Surround Model 78 and Model 79
combination is THX® pm3 approved.
The system’s core design goals were
audio quality and ease of use. Designed
to support the most sophisticated audio
requirements, the signal path was opti-
mized for sonic quality. The operator fea-
tures and controls were carefully selected
to enhance usability and minimize the
learning curve. For the first time, advanced
multichannel monitoring features such as
source selection, level control, downmix,
and bass management are available in a
compact, sonically excellent, and cost-
effective system.
A StudioComm for Surround system starts
with the Model 79 Control Console, a
compact, comfortable “command center,”
that is designed to reside at the operator’s
location. Using a single 9-pin cable, the
Model 79 connects to the Model 78 Central
Controller. The Model 78 occupies just one
rack space and allows connection of two
8-channel inputs and an 8-channel monitor
output. With the StudioComm for Surround
system any audio console, disk-based
recording system, or broadcast facility can
have a complete 7.1 multichannel monitor
system.
Model 78 Central Controller
The Model 78 Central Controller is a
single rack-space unit that contains ana-
log, digital, and power supply electronics.
Two 8-channel analog sources can be
connected. In many applications the first
input, Surround A, will be connected to a
multichannel output on an audio console
or digital audio workstation. The second
input, Surround B, will be connected to a
playback device, such as a multitrack tape
recorder or disk storage system. For film or
video post applications Surround A would
be considered the direct source, while
Surround B would be considered the play-
back source. For flexibility, the inputs are
compatible with balanced or unbalanced
signals having a nominal level range of
–12 dBV to +6 dBu. Fifteen-turn trim po-
tentiometers are used to precisely calibrate
the input signals.
A sophisticated bass management func-
tion is integral to the Model 78’s design.
The overall goal of bass management is
very simple: ensure that the entire audio
bandwidth of all channels can be accurate-
ly monitored. Many loudspeaker systems
have inherent low-frequency limitations,

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preventing a true picture of the source
material from being presented. To overcome
this, the low-frequency energy from the
seven main channels can be separated and
then routed to the subwoofer loudspeaker.
From the factory a general-purpose bass
management configuration is implemented.
In most cases this will provide highly effec-
tive monitoring. To support specialized
applications a technician can revise many
of the bass management parameters, in-
cluding disabling bass management entirely.
The Model 78 provides an 8-channel moni-
tor output to connect to the loudspeaker
system. The outputs are electronically bal-
anced and designed for connection to audio
power amplifiers or amplified loudspeak-
ers. Protection circuitry provides power-up
and power-down protection. Note that while
each of the two surround inputs has an LFE
channel associated with it, the monitor out-
put designates a subwoofer, rather than an
LFE, output. This terminology was carefully
selected to highlight the fact that the output
channel designated for connection to the
subwoofer loudspeaker may have more
than just LFE content. The bass manage-
ment function redirects low-frequency en-
ergy from the main channels, combining it
with the LFE content before routing to the
subwoofer output.
Audio input and output connections are
made using three 25-pin D-subminiature
connectors. The Model 78’s audio path fea-
tures analog switches for input source se-
lection and digitally controlled analog gain
circuits for monitor level control. One 9-pin
D-subminiature connector is used to con-
nect the Model 78 to the Model 79 Control
Console. A second 9-pin “D-sub” connector
is used to interface remote control signals
with the Model 78. An 8-bit microcontroller
provides the logic “horsepower” for the
Model 78. AC mains power is connected
directly to the Model 78, which is factory
selected for 100, 120, or 220/240 V opera-
tion. The internal power supply utilizes two
toroidal mains transformers for quiet audio
operation.
Figure 1. Model 78 Central Controller Front Panel
Figure 2. Model 78 Central Controller Back Panel
Power
present LED
Data
active LED
Input Surround A
trim pots
To/from
Model 79
Control Console
AC mains
connection
Remote control
connections
Input Surround A
connections
Input Surround B
connections
Surround monitor
output connections
Input Surround B
trim pots

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Model 79 Control Console
The Model 79 Control Console is a compact
self-contained unit designed to be located
at the operator’s position. It allows fingertip
control of all monitoring parameters. Numer-
ous LED indicators provide complete status
information. A 4-digit numeric display indi-
cates the monitor output level in real time.
A major strength of the Model 79 is its ability
to configure, under software control, a num-
ber of operating parameters. For example,
during the installation and calibration pro-
cess, the relative levels of the monitor out-
put channels can be adjusted. This helps to
ensure that maximum performance from the
loudspeaker system can easily be obtained.
All configuration parameters are stored in
nonvolatile memory.
The Model 79 provides two buttons and as-
sociated LEDs for selection of the surround
source to be monitored. While in most cases
only one input source will be monitored at
a time, both inputs can be selected for
simultaneous monitoring. This feature can
be useful for creating a rough mix from
the two sources. It is also a fast, effective
means of making a “seat-of-the-pants”
check on the phase relationship between
synchronized signals. For compatibility with
some cinema formats, two buttons and
associated LEDs allow +10 dB of gain to
be added to each input’s LFE channel.
Four downmix modes allow the selected
source to be checked for compatibility
among different formats. The downmix
modes, 5.1, LCRS, Stereo, and Mono,
were implemented primarily for use in
sound-for-picture applications. As such,
from the factory the downmix coefficients
were selected to be effective in these envi-
ronments. However, a technician can easily
change each downmix mode to meet the
specific needs of a facility or audio format.
Figure 3. Model 79 Control Console Front Panel
Downmix
Input mute/solo
Mute/solo
mode select
Monitor Output
• LFE low-pass filter
• Reference level
• Mute all
• Dim
• Rotary level control
Monitor output
level display
Input sources Mains/sub output mute

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An LFE low-pass filter function is provided
as a means of checking the audio content
in the selected input’s LFE channel. The
operator can enable and disable the func-
tion as required, helping to ensure that the
proper signals are being mixed to the LFE
channel. Having the correct mix content is
critical as the LFE channel is often band-
restricted during distribution.
The monitor output level can be controlled
by way of a large, easy-to-use rotary
control. The “curve” or “taper” of the level
control can be configured to match an op-
erator’s preference. The choices available
are true logarithmic and modified logarith-
mic. The level control auto mute-all func-
tion allows the monitor output channels to
automatically mute whenever the rotary
level control is in its fully counterclockwise
(minimum) position. This is useful in ap-
plications such as broadcast. By using the
reference level function, the monitor output
level can set to a preconfigured value. This
is provided for applications that require a
specific monitor level to be quickly select-
ed. The reference level is easily configured
by taking an electronic “snapshot” of the
position of the rotary level control. For op-
erator confirmation, the 4-digit LED read-
out displays the level of the monitor output.
For operator convenience, the dim function
allows the monitor output level to be
reduced by a fixed dB amount. The mute-
all function allows one button to simul-
taneously mute all eight monitor output
channels. The input mute/solo section
provides individual input channel control.
One push-button switch sets the operat-
ing mode for either mute or solo. In the
mute mode, individual input channels can
be muted as required. In the solo mode,
one channel can be monitored while the
others are automatically muted. Depend-
ing on the configuration, multiple channels
can be simultaneously selected for “solo-
ing.” The flexibility of having both input mute
and input solo available allows an operator
to quickly select the most comfortable and
productive operating mode.
Two output mute functions are also provid-
ed. One button allows the seven main out-
put channels to be directly muted. A second
button allows the subwoofer monitor output
channel to be muted. The output mute func-
tion, along with the input mute/solo func-
tion, allows an operator complete flexibility
when checking an input source and its path
to the loudspeaker system. These mute and
solo resources are crucial in a multichan-
nel environment, especially when signals
are passing through a bass management
system.
The Model 79 Control Console connects
to, and is powered by, the Model 78 Central
Controller. The Model 79 generates MIDI
system-exclusive messages to control the
Model 78. Remote-control signals con-
nected to the Model 78 Central Controller
are routed to the Model 79 via pins in the
interconnecting cable.
Remote Control Capability
For flexibility, the StudioComm for Surround
system is designed to easily integrate with
recording consoles, studio communications
systems, and film motion-control electron-
ics. Three remote-control input functions
are provided: mute all, dim, and input
source override. By providing access to the
StudioComm’s mute all and dim functions,
talkback or slate activity from an audio
console or other communications system
can control the monitor output level. The
input source override function is provided
expressly for film post applications, allowing
automatic switching of the StudioComm’s

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input source whenever the mode of a re-
cording system changes between playback
and record. This function, often referred to
as PEC/direct switching, allows accurate
monitoring during dialog replacement or
other overdub sessions.
Channel Assignment and Routing
The Model 78/Model 79 combination is
expressly designed to support 8-channel
7.1 monitoring, with the input channels des-
ignated as left, right, center, LFE, surround
left, surround right, back left, and back right.
While it is anticipated that this channel ar-
rangement will be quite common, the chan-
nels can obviously be used in alternative
arrangements. Using the system with 5.1
sources is perfectly acceptable.
While the StudioComm for Surround system
for multichannel monitoring will do many
wonderful things, it is not designed to selec-
tively route input signals to different output
channels. The input-channel-to-output-chan-
nel relationship is maintained. A signal that
arrives on the SL channel of the Surround
B input will, when selected, output only on
the SL channel of the monitor output. Any
rerouting of the input signals must be done
prior to their connection to the StudioComm
for Surround system. This should not be a
drawback in most facilities, but it is impor-
tant to highlight this fact.
Installation
In this section you will be installing the
Model 78 Central Controller in an equip-
ment rack. Audio input and monitor output
connections will be made. A location will be
selected for the Model 79 Control Console
and it will be connected to the Model 78. If
required, external equipment will be inter-
faced to the remote control inputs. AC mains
power will be connected to the Model 78.
System Components
The shipping carton contains one each of
the following: Model 78 Central Control-
ler, Model 79 Control Console, 20-foot
(6.1 m) 9-pin D-sub interconnecting cable,
and user guide. Units destined for North
America also include an AC mains cord.
Your dealer or distributor should provide
an AC mains cord for non-North American
destinations.
Mounting the Model 78
The Model 78 Central Controller requires
one space in a standard 19-inch (48.3 cm)
equipment rack. Select a location that is
convenient to both the analog audio sig-
nals and the Model 79 Control Console. A
20-foot (6.1 m) cable is supplied to con-
nect the Model 78 to the Model 79. You
can supply your own interconnecting cable,
however 50 feet (15.3 m) is the recom-
mended maximum length. Secure the
Model 78 into the equipment rack using
two mounting screws per side.
Audio Connections
Audio signal connections are made by way
of three 25-pin D-sub connectors, located
on the Model 78’s back panel. Three cable
harnesses, each with a 25-pin D-sub plug
(male) on one end and the desired con-
nectors on the other end, are necessary.
These cable harnesses are not normally
supplied by Studio Technologies. Note that
our friends in some locations may use the
term “loom” instead of harness.
The wiring scheme used by the D-subs
complies with the one made familiar by
TASCAM® with their DA-88® product. Wir-
ing harnesses prepared for connecting to
the surround inputs are identical to DA-88-
style input harnesses. A wiring harness

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prepared for the monitor outputs is identi-
cal to that of a DA-88-style output harness.
Please refer to Figures 4 and 5 for the
exact connection details. Note that unlike
a DA-88-style harness, the Model 78’s
D-sub connectors use 4-40 threads. This
complies with the original design standard
for D-subminiature connectors.
Unless there’s a special need, it may be
cost and time effective for you to purchase
commercially made cable harnesses. Let
the large market for DA-88-style cabling
help you painlessly install your system!
Surround Inputs
The connectors labeled Input Surround A
and Input Surround B are used to interface
with the 16 input circuits. Please refer to
Figure 4 for details on the exact “pin out”
of the D-sub connectors. Each input cir-
cuit is electronically balanced. They are
intended for connection to balanced or
unbalanced sources with nominal signal
levels of –12 dBV to +6 dBu. A 15-turn
trim potentiometer is associated with each
input, allowing the input sensitivity to be
adjusted to match the source’s level. The
configuration section of this guide provides
details on using the trim pots.
Balanced sources should be wired so that
signal high is connected to +, signal low to
–, and shield to the shield connection. With
an unbalanced source, connect signal high
to the + connection, and shield to both the
– and the shield connections. If connecting
to an unbalanced source in this manner re-
sults in hum or noise, try connecting signal
high to +, and shield to –; leave the shield
connection unterminated.
It is highly recommended that at least one
of the surround inputs be wired by way
Signal Signal
Connections High (+) Low (–) Shield
L 24 12 25
R 10 23 11
C 21 9 22
LFE 7 20 8
SL 18 6 19
SR 4 17 5
BL 15 3 16
BR 1 14 2
Notes: 1) Connector type on Model 78 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 Inputs Surround A
and Surround B
Signal Signal
Connections High (+) Low (–) Shield
L 24 12 25
R 10 23 11
C 21 9 22
LFE 7 20 8
SL 18 6 19
SR 4 17 5
BL 15 3 16
BR 1 14 2
Notes: 1) Connector type on Model 78 is 25-pin D-subminiature
female. Installer must provide plug (male). Connector
uses 4-40 threaded inserts for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-type wiring harnesses are directly
compatible, with the exception of 4-40 screw threads
being required.
Figure 5. Connections for Monitor Output

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of an audio patch bay. This will allow the
channels associated with that input source
to be easily rerouted. While signals gener-
ated within a facility will normally follow a
specific format, such as L, R, C, LFE, SL,
SR, BL, and BR, it is possible that media
provided by an outside facility will follow a
different one.
Monitor Output
The connector labeled output provides
access to the 8-channel monitor output.
Please refer to Figure 5 for details on the
exact “pin out” of the D-sub connector.
The monitor output channels are intended
for connection to audio amplifiers associ-
ated with monitor loudspeakers, or to the
inputs of loudspeakers that contain inte-
grated amplifiers. The monitor outputs are
electronically balanced and capable of
driving balanced or unbalanced loads of
600 ohms or greater. While balanced op-
eration 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 unbal-
anced 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 78’s electroni-
cally balanced output circuits are capable
of driving loads of 600 ohms or greater,
the output level will drop slightly as the
load impedance approaches 600 ohms.
A 0.5 dB difference in output level can be
expected as the load impedance changes
from 10 k ohms to 600 ohms.
Remote Control Inputs
Support is provided for three remote con-
trol input functions: mute all, dim, and input
select. The inputs use logic gates, “pulled
up” to +5 V by way of resistors, which are
active when brought to the 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 configured to
change state (“latch”) in response to a
logic pulse.
The connector labeled Remote Control
Inputs on the back panel of the Model 78
is used to interface with the remote control
inputs. Refer to Figure 6 for exact connec-
tion details. Note that pin 1 (Shield) and
pin 9 (Remote Control Common) are elec-
trically identical. In addition to connecting
to system common, they connect to the
Model 78’s chassis and mains earth con-
nection. For convenience, the shield of the
interconnecting cable should be connected
to pin 1 (Shield), while the return signals of
the remote control sources should connect
to pin 9 (Remote Control Common).
Note that although the remote control con-
nections are physically made to the D-sub
on the Model 78’s back panel, the remote
control input circuitry is actually located in
the Model 79 Control Console. Conduc-
tors in the cable linking the Model 78 to the
Model 79 route the remote control signals
to the actual input circuitry.

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Connecting the Model 78 to
the Model 79
A cable with 9-pin D-sub plugs (males)
on each end is used to interconnect the
Model 78 Central Controller with the
Model 79 Control Console. A 20-foot (6.1-
meter) cable is provided with each system.
The connector labeled To/From Control
Console on the back panel of the Model 78
is used to connect to the Model 79.
Should a cable of different length be re-
quired, it should be wired in a one-to-one
fashion for all 9 pins. Pin 1 carries signal
common, and must be connected at both
ends. A shield connection for the cable
should be connected to pin 1 on the Model
78’s end. For best performance the cable
generally should not exceed 50 feet (15.3
meter) in length. The reality is that a cable
much longer in length should work correct-
ly, as long as an excellent-quality cable is
utilized. We define “excellent” as extensive
shielding along with very low capacitance.
The low cable capacitance is important
as it limits the amount of data-signal
waveform distortion. As far as an actual
maximum length, just test and see how far
away you can go—if it works, it works!
AC Mains Power
The Model 78 is internally configured to
operate from either nominal 100, 120,
or 220/240 V, 50/60 Hz. Units shipped to
North America are factory selected for
120 V operation. Units bound for Japan
are generally selected for 100 V, while
our friends “down under” and in Europe
receive units set for 220/240 V. Before
connecting the Model 78 to AC mains
power, check that it is configured to match
the local mains voltage. Look on the back
panel (adjacent to the power entry con-
nector) for the factory-configured voltage.
Note that an incorrect configuration could
prevent operation, or cause damage to the
unit. Should it be necessary to change the
unit’s operating voltage it must be per-
formed only at the factory, or by a factory-
authorized service technician.
The Model 78 uses an IEC-standard
connector to mate with the AC mains
cord. The wire colors in the AC mains
cord should conform to the internationally
recognized CEE color code and must
be wired accordingly:
Connection Wire Color
Neutral (N) Light Blue
Line (L) Brown
Protective Earth (E) Green/Yellow
Safety Warning: The Model 78 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.
Pin Signal
1 Shield
5 Remote Mute All
6 Remote Dim
7 Remote Input Select
9 Remote Control Common
Notes: 1) Connector type on Model 78 is 9-pin D-subminiature
female. Installer must provide plug (male). Connector
uses 4-40 threaded inserts for locking with mating plug.
Figure 6. Connector Pin Out for Remote Control
Inputs

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As soon as AC mains power is applied, the
Model 78’s power present LED will light.
The Model 79 will go through a power-up
sequence, lighting each LED in secession.
The Model 79’s software revision level will
also display momentarily. The data active
LED on the Model 78 will briefly light upon
completion of the Model 79’s power-up
sequence.
Configuration
After the physical installation has been
completed, several configuration issues
must be addressed. On the Model 78 the
surround inputs must be calibrated using
the trim potentiometers. The operating pa-
rameters of the system should be set using
the Model 79 Control Console’s configura-
tion mode. Using the Model 79’s calibration
mode, output channel level offsets can be
configured if desired.
Input Level Calibration
Sixteen 15-turn trim potentiometers are
located on the front panel of the Model
78 Central Controller. Taking time to care-
fully adjust the trim pots will ensure that
accurate monitoring can take place. Each
trim pot allows input signals with a nominal
level of –12 dBV to +6 dBu to be utilized.
With care, it’s easy to calibrate the sur-
round inputs to within one-quarter of a dB
of the desired value.
The monitor outputs are used as the mea-
suring point when adjusting the trim pots.
A laboratory-grade audio level meter,
or equivalent, is required for accurate
calibration. In addition, the audio sources
connected to the inputs must be able to
generate continuous audio signals at their
nominal operating level.
Procedure
This procedure will calibrate the surround
input channels. The trim pots will be ad-
justed in groups corresponding to their
associated input source.
1. Begin by turning the audio amplifiers
or amplified speakers to their off state.
This will protect the loudspeakers and
the operator’s ears from possible
damage.
2. Rotate the level control on the Model
79 to the fully clockwise (maximum)
position.
3. Using the Model 79 Control console,
select Surround A as the input source.
4. On the Model 78, connect the audio
level meter to the left channel of the
monitor output.
5. Confirm that the audio source’s left
channel is generating a steady signal
at precisely its reference level.
6. Observing the level meter, adjust trim L
for Surround A to give the desired level
at monitor output L. This level may be
+4 dBu, +14 dBu, or some other value
depending on the configuration of the
output level range.
7. Disconnect the level meter from the left
channel of the monitor output.
8. Repeat steps 4-7 for the other seven
channels of Surround A.
9. Repeat steps 3-8 for the channels as-
sociated with Surround B.
10. Rotate the level control on the Model
79 to the fully counterclockwise (mini-
mum) position.

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11. After ensuring that the Model 79’s level
control is set to minimum, return AC
mains power to the power amps or
amplified speakers.
Model 79 Operating
Parameters
Many StudioComm functions can be
configured to meet the exact needs of your
installation. Here’s an overview of what you
can configure:
• Input channels active
• Solo mode
• Power-up mute all
• Level control response
• Level control auto mute all
• Output level offset
• Output level range
• Reference level
• Dim level
• Downmix modes
• Remote control inputs
The Model 79 configuration diagrams,
located at the end of this section, give
details on how each parameter is set. An
overview of each configurable parameter
is provided in the following paragraphs.
Entering and Exiting the Configuration
Mode
A small button is located on the back of the
Model 79 Control Console, adjacent to the
9-pin D-sub connector. Pressing and hold-
ing this button for two seconds places the
Model 79 into the configuration mode. In
the configuration mode the Model 79’s ar-
ray of buttons and LEDs no longer perform
their normal functions, but instead allow
you to observe and change many of the
operating parameters. The mute/solo mode
LEDs light alternately to indicate that the
configuration mode is active.
To leave the configuration mode and return
the Model 79 to normal operation, once
again press and hold the configure button
for two seconds. Note that configuration
changes are stored only after the configu-
ration 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 to acciden-
tally activate. We didn’t want normal opera-
tion to cease because someone pushed
the Model 79 into a “rats nest” of music
scores or track sheets!
There is no problem frequently “tweak-
ing” the Model 79’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.
Input Channels Active
The configuration parameter for the num-
ber of channels active for each input is pro-
vided for those cases where a source has
less than eight channels. Let’s look at an
example. Surround A is connected to an
8-channel source, so its default configura-
tion is fine. But the source for Surround B
is different, having only six channels: left,
right, center, LFE, surround left, and sur-
round right. This makes it not so “cool”
for the operator to select Surround B for
monitoring, as the unconnected back
left and back right input channels will get

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routed to their respective monitor outputs.
Will the unused input channels pick up
significant noise or hum? Unlikely, but why
take a chance at having a problem. Simply
use the input channels active configuration
to disable the two unused channels. Now
when Surround B is selected, only the rel-
evant channels are selected for monitoring.
Note that when a channel associated
with an input is disabled, the input routing
circuitry, under software control, no longer
selects it, but the corresponding monitor
output channel does not mute. With our
example, when selecting Surround B, our
mythical 5.1 source, all monitor output
channels will remain active, but the input
routing circuitry won’t select the BL and
BR inputs. While to some people this might
seem confusing and possibly a design
fault, it was implemented this way because
the StudioComm system allows both
inputs to be simultaneously selected for
monitoring; a 7.1 source might be selected
at the same time as a 5.1 source. Muting
the outputs simply would not do!
A special mode has been included to
allow an input to be disabled from being
accessed by the operator. This might be
useful, for example, when Surround B is
not connected to a source, and has no
valid reason to be selected. This might
also be useful when connecting a special
source, such as a house “tie line” or router
output, that shouldn’t normally be acces-
sible. To disable an input is simple, just
disable all eight channels associated with
it. To confirm that an input has been dis-
abled, all LEDs associated with that input
will flash on and off. Once the Model 79 is
returned to the normal operating mode, the
disabled input cannot be selected.
Solo Mode
Solo operation can be configured to sat-
isfy operator preference. The additive solo
mode matches the functionality found in
many recording consoles. In this mode,
multiple channels can be simultaneously
“soloed,” allowing those channels to be
monitored at the same time. Other opera-
tors may prefer the exclusive solo mode.
When this mode is selected, only one
channel can be selected for solo at a
time. The additive solo mode is the default
setting.
Power-up Mute All
By default, upon application of AC mains
power the monitor outputs remain muted
after the system’s power-up sequence
has been performed. Then an operator
must manually press the mute all button
to enable the monitor outputs. There may
be cases where it’s desirable to have the
monitor output channels return to their
respective states as left at the time of the
previous loss of AC mains power. This
would allow normal operation to automati-
cally resume.
Level Control Response
As expected, the level control on the Model
79 Control Console is used to adjust the
output level of the monitor output channels.
The amount of rotation required to reach a
specific level can be selected. This can be
described as allowing the “curve” or “taper”
of the level control to be configured. Two
choices are available: true logarithmic and
modified logarithmic. In the true logarithmic
mode the level control provides a precise
logarithmic performance over its entire
rotation, e.g., the output level is half of its
maximum when the control is set at its
midpoint, i.e., 50% of its “travel.” In the

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true log mode, normal listening may
require the level control to be set to ap-
proximately the 2-o’clock position. Other
users may be more comfortable with the
response given by the modified logarithmic
mode. This provides a much greater out-
put level during the first 50% of the level
control’s travel. When configured for the
modified log mode, normal listening may
require the level control to be set to the
11- or 12-o’clock position. The modified log
mode more closely matches the monitor
level control performance found in many
audio consoles. As such it is selected as
the default mode.
It’s important to note that changing the
level control response configuration will
impact the reference level. Changing from
modified log to true log, or vice-versa, will
change the reference level. Technically, the
mathematical value stored as the refer-
ence level does not change, but the result-
ing loudness that is heard by the operator
will change. Be warned! Changing the level
control response may require the reference
level to be re-calibrated.
Level Control Auto Mute All
The level control auto mute all function
automatically mutes the monitor output
channels whenever the rotary level control
is in its fully counterclockwise position. In
some applications it may be desirable to
disable this function. When disabled, the
rotary level control adjusts the monitor out-
put level over the configured level range;
no automatic muting takes place.
Output Level Offset
To provide assistance during room calibra-
tion, the relative output levels on seven
of the eight output channels can be adjust-
ed. The exact calibration procedure
is covered later in this document. A con-
figuration parameter selects whether the
output level offset function is set for view
only, or view and change. The view only
mode allows users to view the level offset
settings, but serves as a “lock out,” prevent-
ing a calibrated system from accidentally
being changed. Unless the level offsets are
actively being adjusted to their desired val-
ues, it is recommended that the view
only mode be selected.
Output Level Range
To meet the needs of different applications
the output level range can be selected. In
mode 1 the input-to-output level has a min-
imum gain of –70 dB and a maximum gain
of unity (0 dB). When the rotary control is
set to its fully counterclockwise position,
–70.0 will display on the readout. Set to
its fully clockwise position, 0.0 will display.
In mode 2 the input-to-output level has a
minimum gain of –80 dB and a maximum
gain of –10 dB. The display will read over a
range of –80.0 to –10.0.
Reference Level
For audio-with-picture applications it’s criti-
cal that mixing be done in reference to
a known monitor loudspeaker level. This
is often referred to as mixing to “85 dB” on
the monitors. The Model 79 Control Con-
sole allows a precise monitor output level
to be stored, and then enabled by pressing
the button labeled REF. Setting the refer-
ence level is very simple:
1. Set up a precision sound pressure level
(SPL) measuring device at the desired
listening location.
2. Place the StudioComm system in the
normal operating mode, not the config-
uration mode. Be certain that the refer-
ence and dim functions are not active.

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3. Use the Model 79 Control Console to
select the input source that contains
the desired reference signal source,
e.g., pink noise.
4. Observing the SPL meter, adjust the
Model 79’s rotary level control until
the desired reference output level has
been reached.
5. Being careful not to touch the position
of the rotary level control, enter the
configuration mode by pressing and
holding the configuration button locat-
ed on the Model 79’s back panel.
6. Once the configuration mode has been
entered, the monitor outputs will mute.
Press and hold the reference button
until its associated LED lights. This will
take approximately 5 seconds. The
LED will light to indicate that a “snap-
shot” of the new reference level has
been taken. The level display will show
the exact reference level that is being
stored.
7. To store the new reference level in
memory, exit the configuration mode
by again pressing and holding the
configure button.
This level is now permanently stored as
the reference level. Only by repeating the
procedure can the value be changed.
Once the configuration mode has been
exited, the monitor output channels will
again become active. Confirm that the cor-
rect level has been stored by pressing the
reference button. The SPL meter should
again display the desired level. If not,
repeat the calibration procedure.
You might wonder why you have to press
and hold the reference button for 5 sec-
onds before the selected value is stored.
This is provided specifically so that some
turkey won’t accidentally change the refer-
ence level while they are playing around in
the configuration mode! Only if you know
the “secret” will you be able to store a new
value.
Dim Level
The dim function is used to reduce the
monitor output level by a preset amount.
The reduction is in dB relative to the monitor
output’s current level. There are four dim
level values available: 10, 15, 20, and 25 dB.
Downmix Stereo Mode
There are two modes available for the
downmix stereo mode. The difference
between the two modes relates to how
the sum of the SL, SR, BL, and BR chan-
nels are routed to the L output channel. In
mode 1 the sum of the signals are inverted
and then routed to the L output. In mode 2
the sum of the signals are directly routed
to the L output. Mode 1 is default and is
recommended for THX® monitoring appli-
cations. Mode 2 may be more appropriate
for general audio monitoring applications.
For details on the downmix stereo modes
please refer to the Technical Notes section
of this guide.
Downmix Mono Mode
There are two modes available for the
downmix mono mode. In mode 1 the L, R,
and C channels are summed and routed to
the C output channel. In mode 2 in addition
to the L, R, and C channels, the sum of the
SL, SR, BL, and BR channels are routed
to the C output. Mode 1 is default and is
recommended for THX® monitoring applica-
tions. It may also be appropriate for some
audio-with-picture applications. Mode 2 may
be useful for general audio monitoring appli-
cations. Refer to the Technical Notes section

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Page 18 Studio Technologies, Inc.
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of this guide for details on the downmix
mono modes.
Remote Mute All
Two configuration choices are associated
with the remote mute all function: disabled
and enabled. To utilize the function simply
configure it for enabled.
Remote Dim
Two configuration choices are associated
with the remote dim function: disabled and
enabled. To utilize the function simply con-
figure it for enabled.
Remote Input Select
The remote input select function requires
configuring two parameters: mode and
input to be selected. The mode can be
selected from three choices: disabled,
exclusive, and non-exclusive. As expected,
when configured for disabled, the function
can’t be activated. When configured for
exclusive, whenever the function is acti-
vated only the specified input will be active.
When configured for non-exclusive, when-
ever the function is activated the specified
input will be added (summed) with the
other input, if it is already active.
Restore Factory Defaults
The restore factory defaults function is pro-
vided 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. Spe-
cifically, 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!
Output Channel Level Offset
To provide assistance during room calibra-
tion, the relative output levels of seven of
the eight output channels can be adjusted
over a limited range. The L, R, Sub, SL,
SR, BL, and BR channels can be adjusted
in 0.5 dB steps over a ±6 dB range. The
center (C) output channel is used as a
reference and cannot be adjusted.
Begin the level offset calibration proce-
dure by entering the offset level calibration
mode. Starting from the normal operating
mode, press and hold both the mains mute
and sub mute buttons. After five seconds
the system will enter the level offset cali-
bration mode. This is indicated by the solo
mode LED flashing on and off. In this
mode the input mute/solo channel buttons
are used to display the current level offset
values and, if the system is configured for
view and change, will allow the displayed
value to be changed. The displayed value
represents the dB level difference as
compared to the center output channel.
The range is –6.0 to 6.0 in 0.5 dB steps. All
other system functions will operate normal-
ly. The monitor output will be active, allow-
ing real-time adjustment of the level offset.
Changing an offset level will directly impact
the monitor output level for that channel.
If the Model 79’s configuration has been
selected for view only, pressing a channel
button during the calibration mode will only
display the level offset value. No changes
can be made. If the configuration is set for
view and change, the mains mute and sub
mute buttons can be used to adjust the lev-
el offset. The buttons are active only when
a channel button is pressed. The mains
mute button will reduce the output level
in 0.5 dB steps. The sub mute button will
increase the output level in 0.5 dB steps.

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Studio Technologies, Inc. Page 19
for Surround
Note that pressing the button associated
with the center channel will always display
a level offset value of 0.0. This value is
fixed and cannot be changed. This is due
to the fact that the center channel serves
as the system reference.
Once the level offset calibration process
has been completed, exit the calibration
mode by pressing and holding the mains
mute and sub mute buttons for five sec-
onds. To prevent the level offset values
from being accidentally changed, the main
Model 79 configuration mode should be
entered and the view only mode selected.

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Model 79 Configuration—Entering and Exiting
Configuration Mode
Press and hold the configuration
button for 2 seconds to enter or
exit the configuration mode.

These LEDs will light alternately
when configuration mode is active.