Studio Technologies 55 User Manual

Model 55 Central Controller,

Model 56 Control Console ,

and Related Components

User Guide

Issue 3, December 1996

This User Guide is applicable for serial numbers:

Model 55 M55-00151 and later
Model 56 M56-00151 and later

© 1996 by Studio Technologies, Inc., all rights reserved

5520 West Touhy Avenue

Skokie, Illinois 60077 U.S.A.

Telephone [phone]

Fax [phone]

www.studio-tech.com

50063-1296, Issue 3

Issue 3, December 1996 Model 55/56 User Guide
Page 2 Studio Technologies, Inc.

Tab le of Contents

Foreword

Introduction ................................................................. 7

What This User Guide Covers ................................ 7

System Overview .................................................... 7

System Features ..................................................... 8

Installation ................................................................... 12

Configuration............................................................... 17

Model 56 Configuration Chart—Main Functions ..... 2 1

Model 56 Configuration Chart—

Alternate Functions ............................................ 22

Operation .................................................................... 23

Model 55 Central Controller .................................... 2 3

Model 56 Control Console....................................... 23

Talent Amplifiers ..................................................... 2 5

Troubleshooting .......................................................... 26

Technical Notes .......................................................... 28

Specifications .............................................................. 3 3

Appendix A.................................................................. 36

MIDI Messages ....................................................... 38

Block Diagrams

Model 55 Central Controller

Model 56 Control Console

Model 35/Model 38 Talent Amplifiers

Model 70 Interface

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Issue 3, December 1996 Model 55/56 User Guide
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Forew ord

I am pleased to present the StudioComm series of products. As both president and owner
of Studio Technologies, I take a very personal approach when designing products. Getting
older (40 as of this writing) has increased my appreciation of the more subtle things in
life—be they a part of nature or the nuances contained in a well-designed piece of elec­tronic equipment. Do the technical and operational aspects of a product work together
to “feel” right? A Studio Technologies’ design is ready to go only when I am completely
satisfied. My entire focus for the StudioComm series was to make a system that you’d
really enjoy using, and one that would perform reliably for years. I hope you share my
enthusiasm.

Many fine people worked toward making the StudioComm “happen.” Mitch Budniak (ace
consulting engineer) designed many of the circuits. Jim Cunningham contributed to the
analog design. Carrie Loving provided engineering support. Barbara Govednik coordinated
the marketing communications aspects. Ben Kamen designed the automatic testing rou­tines. Larry Leviton wrote the excellent micro-controller software. Al Lux designed
the printed circuit boards. Jim McGuire designed the graphics. Fred Roeck performed the
mechanical design. Joe Urbanczyk coordinated the safety testing and agency approvals.

Many thanks to Bob Tjarks, professional audio sales manager at Gand Music & Sound,
Northfield, Illinois. Bob brought to my attention the need for a product to serve digital audio
workstations. His product idea evolved into the StudioComm series. Additional thanks to
Timothy Powell of Metro Mobile Recording, Glenview, Illinois, who provided his excellent
ears when issues of sonic quality arose. His extensive field and studio experience was
extremely helpful in keeping me on the audio “straight and narrow.”

Please contact me with your questions, comments, and suggestions. I can be
reached by voice at [phone], fax at [phone], or via the Internet
@ www.studio-tech.com.

Sincerely,
Gordon K. Kapes

President

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Issue 3, December 1996 Model 55/56 User Guide
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Introduction

The Model 55 Central Controller, along
with the companion Model 56 Control
Console, are members of the StudioComm
family of products. The Models 55 and 56
are specifically designed to work in con­junction with digital audio workstations to
provide a full set of monitoring and com­munications functions. Features include
control room monitoring, meter output, an
integrated headphone system, dubbing,
and communications functions that include
talk to phones and slate. All StudioComm
functions perform to a level that rivals
even the largest recording consoles. Many
of the functions are user configurable,
allowing unmatched flexibility.

What This User Guide Covers

This User Guide is designed to assist you
when installing, configuring, and using
the Model 55 Central Controller, Model 56
Control Console, Model 35 Talent Ampli­fier, Model 38 Talent Amplifier, and related
components. A limited amount of trouble­shooting and background technical infor­mation is also provided. Should you
require detailed technical information
please refer to the StudioComm Service
Guide covering the Models 55, 56, 35, and

38. The Service Guide contains detailed
service information, including schematic
diagrams. The Service Guide is not
shipped with each StudioComm system,
but is available from the factory upon
request. It is free of charge to purchasers
of StudioComm equipment. Give us a call
or send a fax if you need this highly excit­ing document!

System Overview

A complete StudioComm system consists
of a rack-mounted central controller, a
desktop control console, and one or more
portable talent amplifier units. The Model
55 Central Controller and the Model 56
Control Console work together, intercon­necting using a standard 5-pin MIDI-style
cable.

Circuitry in the Model 55 routes any of
four stereo inputs to the control room,
meter, headphone, and dub outputs, with
commands provided by the Model 56
Control Console. The Model 56 Control
Console’s built-in microphone lets you
talk to the headphone output. It also allows
you to talk to the dub output, or to the dub
and headphone outputs using the slate
function.

The Model 35 Talent Amplifier is a por­table amplifier unit capable of driving one
or two pairs of high-impedance stereo
headphones. A single microphone-type
cable links the Model 35 with the Model 55
Central Controller. The Central Controller
provides power and left and right audio
over just three wires.

The Model 38 Talent Amplifier takes the
basics from the Model 35 and adds a
unique stereo preamplifier section. This
allows each Model 38 user to create an
individual headphone mix, solving the
classic problem of wanting “more me” in
the phones! Like the Model 35, the Model
38 is linked to the Model 55 Central Con­troller by a single microphone-type cable.

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System Features

Stereo Line Inputs

The Model 55 contains four stereo line­level inputs which are compatible with both
balanced and unbalanced signals. Each
input is independently software config­urable for a nominal input level of –10dBV
or +4dBu. This allows direct connection
with virtually any audio source. Each input
can also be configured to operate as a
mono input. In this manner, a signal
connected to the left input is routed to both
the left and right outputs.

Control Room Monitoring

The control room section provides a ste­reo line-level output for driving a power
amplifier associated with monitor loud­speakers. Four buttons are used to select

the input source to be monitored. Nor­mally, only one of the four input sources is
selected for monitoring. For special appli­cations, the system can be configured to
allow two input sources to be simulta­neously monitored. The control room level
is adjusted using a smooth-feeling rotary
potentiometer. The Dim button allows the
control room level to be temporarily re­duced. The Mono button allows the sum
(L+R) of the selected source to be sent as
the control room output.

Meter Output

The meter output provides a stereo output
that “follows” the source(s) selected for the
control room. The signal is not affected by
the control room level circuitry, but is
“post-mono.” The meter output is intended
to be connected to VU- or PPM-type meter

Model 55 Front Panel

Power

present LED

Model 56 Control Console

and Talent Amplifier

over current LED

Model 55 Back Panel

AC mains

connection

Mains voltage

configuration chart

Input data

present LED

To/from Model 56

Control Console

Output to talent

amplifiers

Meter

output

Dub

output

Control room

output

Stereo line

inputs 1-4

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panels that contain series current-limiting
resistors or input buffer amplifiers.

Dub Output

A stereo line-level output is provided as a
dub (copy) output. Any of the four inputs
can be assigned to the dub output. The
slate function allows communications
(voice) audio to be sent out the dub output.

Communications Functions

The Model 56 Control Console contains
an internal microphone that is used in
conjunction with the two communications
functions. The talk to phones function
either interrupts the phones source or adds
(sums or mixes) to the phones source. The
slate function interrupts the dub source
and, if configured, the headphone source
and connects communications audio. The
audio level of each communications func­tion is individually adjustable.

• Each of the four stereo line inputs can

be independently set for –10dBV or
+4dBu operating levels.

• Each input can be set for either mono

or stereo operation. In the mono mode
a signal connected to the left input is
sent to the left and right outputs.

• The dub output level can be set for a

nominal –10dBV or +4dBu output level.

• Unique to the system is the ability to

configure the dim level to one of three
values, allowing a 15, 20, or 25dB
reduction when dim is active.

• Three functions can be set for push-to-

latch operation if desired: talk to
phones, slate, and control room mono.

• The auto dim off function, when config-

ured, allows any change in the control
room level potentiometer to automati­cally turn off an active dim state.

MIDI Control

All Model 55 Central Controller functions
are controlled using system-exclusive
MIDI messages. The Model 56 Control
Console “speaks” this language, and in
most applications a Model 56 will be uti­lized. In special applications the Model 55
Central Controller can be connected
directly to a MIDI bus, allowing the creation
of a fully automated recording or audio
routing system. For more information on
MIDI support, refer to Appendix A.

Configuration

The Model 56 Control Console can be
configured to make the system meet a
user’s exact operating environment. All
configuration parameters, along with
“power down” operation conditions, are
stored in nonvolatile memory.

• The slate function can be configured to

talk to the dub output, or talk to both the
dub and headphone outputs.

• The talk to phones function can be set

to interrupt the normal phones source or
add (sums) to the phones source.

• The system can be configured to allow

only one input source, or one or two
input sources to be selected as the
control room source(s).

Headphone Monitoring

The StudioComm system contains an
integrated, full-featured headphone (cue)
system. Up to four Model 35 or Model 38
Talent Amplifiers can be connected to
the Model 55’s talent amplifier output. A
single 3-conductor microphone-type cable
carries power and stereo audio.

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Model 56 Front Panel

Configure button switches
between normal operation

and configure mode

Built-in microphone for
communications functions
(talk to phones, slate)

Source selection

for control room (CR),

headphones, and dub;

three columns of LEDs

show the currently

selected sources

Model 56 Back Panel

Change the control room
level; listen in mono
(L+R); or reduce the level
by a preset amount

Talk to the headphones;
slate; set communications
levels

Connection

to the Model 55

Central Controller

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Using the Model 56 Control Console,
any of the four stereo inputs can be as­signed to the talent amplifier output. The
talk to phones and slate functions allow
communications (voice) audio to be sent
to the talent amps. The talent amplifier
output is short circuit protected. Error
conditions are displayed by the Over
Current LED on the Model 55’s front
panel.

Model 35 Front Panel

Each Model 35 and Model 38 Talent
Amplifier can drive two sets of high­impedance headphones (>150Ω). The
audio output is loud, and very “clean.”
The units feature a built-in level control,
a stereo/mono switch, and a power
present LED.

The Model 38 Talent Amplifier takes the
basics from the Model 35 and adds a
unique stereo preamplifier section. This

Power present

LED

Headphone output

level control

Switch between

stereo and mono

(L+R) output

Two headphone

outputs

Model 35 Back Panel

Connects to additional

talent amplifiers

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Connects to the Model 55 or another talent

amplifier’s loop thru connector

allows a musician’s microphone or line­level signal to be “looped” through the
Model 38, boosted by its preamp, and then
combined with the stereo cue mix supplied
by the Model 55. This provides each
Model 38 with an individual headphone
mix, solving the classic problem of wanting
“more me” in the phones! Like the Model
35, the Model 38 is linked with a Model 55
Central Controller by a single cable.

Model 38 Front Panel

Installation

In this section you will be installing the
Model 55 Central Controller in an equip­ment rack. Audio input and output connec­tions will be made using the Model 55’s
multitude of jacks. One or more Model 35
or Model 38 Talent Amplifiers may be
connected. A location will be selected for

Power present

LED

Mic/Line button switches

the talent input between

microphone and line level

Model 38 Back Panel

Connects to additional

talent amplifiers

Talent level

to phones

Connects to the Model

55 or another talent
amplifier’s loop thru

connector

Switch between

stereo and mono

(L only) for the

talent input

Loop thru connectors parallel the

talent inputs for routing to a digital

audio workstation, effects device,

microphone preamp, etc.

Cue mix

level to
phones

Two headphone outputs

Switch between stereo

and mono (L+R) for

the cue mix

Connects to talent

sources such as key-

boards or microphones

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the Model 56 Control Console, and it will
be connected to the Model 55. AC mains
power will be connected to the Model 55.

System Components

The main StudioComm shipping carton
contains a Model 55 Central Controller,
Model 56 Control Console, 5-conductor
MIDI-style cable, User Guide, and war­ranty card. Units destined for North
America are shipped with an AC mains
cord. Your dealer or distributor will provide
an AC mains cord for non-North American
destinations. Model 35 and Model 38
Talent Amplifiers, along with accessories,
will be contained in separate cartons.
Please check to ensure you have every­thing you need.

Mounting the Model 55

The Model 55 requires one space in a
standard 19-inch (48.3cm) equipment
rack. Select a location near where the
Model 56 Control Console will be located.
A cable is provided to connect the Model
55 to the Model 56. You can supply a
longer cable, however 50 feet (15.3m) is
the recommended maximum length. It is
desirable to locate the Model 55 to allow
easy access to both the front and the back
panels. The back panel contains all of
the input and output connectors, while
the front panel contains several LED
indicators. The Model 55 is secured to
the equipment rack using two mounting
screws per side.

Audio Inputs and Outputs

The Model 55’s line-level audio input and
output connections are made using ¼-inch
3-conductor phone jacks. Don’t be con­cerned about our use of phone jacks as
part of a “professional” product. The jacks

Balanced Connection

(Input & Output)

Ring (–)

Tip ( + )

Sleeve

(Shield)

(Switchcraft No. 297, Neutrik NP3C, or equivalent)

used are manufactured by Neutrik, and
feature gold-plated contacts for high reli­ability.

Caution: For reliable audio intercon­nection, the plugs you use must comply
with industry standard RS-453.
Switchcraft No. 297, Neutrik NP3C, or
equivalent will work correctly. Refer to
the Technical Notes section for details.

Stereo Line Inputs

The Model 55 provides four stereo line­level inputs. Each input is electronically
balanced, and can be configured for com­patibility with –10dBV or +4dBu signal
levels. The Model 56 Control Console
gives you push-button control, so you can
easily change input sensitivities at any
time (refer to the Configuration section
under Input Sensitivity). Monaural sources
should be connected to the left (L) input
and configured for mono operation (refer
to the Configuration section under Stereo/
Mono Input).

Prepare the mating connectors (plugs)
so that tip is signal high (+ or hot), ring is
low (– or cold), and sleeve is shield. With
an unbalanced source connect the tip to

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Studio Technologies, Inc. Page 13

high (+ or hot), and both the ring and
sleeve to shield. If connecting to an
unbalanced source in this manner results
in hum or noise, connect tip to high (+ or
hot) and ring to shield; leave the sleeve
unterminated.

The meter output utilizes two ¼-inch
3-conductor phone jacks for interconnec­tion. Prepare the mating connectors
(plugs) so that tip is signal high (+ or hot),
sleeve is low (– or cold); ring is not con­nected.

Control Room Output

The Model 55 contains a stereo line-level
output for connection to an audio power
amplifier. This audio amplifier serves a
pair of loudspeakers that are located in the
control room. (Of course the control room
output can be connected to loudspeakers
that contain integral power amplifiers, such
as the products from Genelec.)

The output is electronically balanced and
capable of driving loads of 600 ohms
or greater. In most situations best perfor­mance will be obtained if the audio amp­lifier’s input sensitivity is set to near
maximum. Refer to the Technical Notes
section for details on setting amplifier
sensitivity.

The control room output utilizes two
¼-inch 3-conductor phone jacks for inter­connection. Prepare the mating connec­tors (plugs) so that tip is signal high (+ or
hot), ring is low (– or cold), and sleeve is
shield. To connect to an unbalanced load
connect the tip to high (+ or hot), and both
the ring and sleeve to shield.

Meter Output

The meter output is intended to be con­nected to a VU- or PPM-type meter panel
that contains input buffer circuitry or series
current-limiting resistors. Each output is
unbalanced, has a nominal level of +4dBu,
and is capable of driving loads of 2k ohms
and greater.

Dub Output

The Model 55 contains a stereo line-level
output which is intended for connection to
a variety of analog audio devices. The dub
output is electronically balanced and cap­able of driving 600 ohm loads or greater.
With the input impedance of most audio
devices at 10k ohms or greater, the dub
output can easily drive 10 or more devices
simultaneously.

The dub output can be configured for a
nominal level of –10dBV or +4dBu, so you
can connect to all line-level inputs with no
hassle (refer to the Configuration section
under Dub Output Level ) .

The dub output utilizes two ¼-inch
3-conductor phone jacks for interconnec­tion. Prepare the mating connectors
(plugs) so that tip is signal high (+ or hot),
ring is low (– or cold), and sleeve is shield.
To connect to an unbalanced load connect
the tip to high (+ or hot), and both the ring
and sleeve to shield.

Talent Amplifier Output

Up to four Model 35 or Model 38 Talent
Amplifiers can be connected in any combi­nation to the Model 55’s talent amplifier
output. The output connector is a 3-pin
male XLR-type. For best performance,
use low-capacitance shielded microphone­type cable to distribute the talent amplifier
signal. If you have a choice, select cables
with the heaviest wire gauge commonly
available. This will reduce voltage drop

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when using long cable runs. Refer to the
Technical Notes section for additional
information.

The simplest installation would use a
microphone cable to connect the Model 55
to the first talent amplifier; the loop through
connector on that talent amp sending the
signal on to the next talent amp.

For convenience, you may want to wire
your facility to allow easy access to the
talent amplifier signal at all locations
where talent amplifiers might be used. The
talent amplifiers connect to the Model 55
in parallel, so the connectors on the distri­bution panels or mult boxes must be wired
in parallel.

Warning: Do not connect the Model
55’s talent amplifier output to anything
but Studio Technologies’ talent amplifi­ers. Some audio equipment may be
damaged by the +23Vdc contained on
pin 2 of the talent amplifier output
connector.

Several mounting options are available for
the Model 35 and 38 Talent Amplifiers. For
details refer to Mounting Options in this
section.

In special cases you may need to obtain
a stereo, balanced line level output signal
from the Model 55 talent amplifier output.
The Model 70 Interface is available for this
purpose. For details refer to the end of this
section.

Locating the Model 56 Control Console

The Model 56 was designed for desktop
use, however provision has also been
made for microphone-stand mounting.
For details refer to Mounting Options in
this section.

Connecting the Model 55 to the
Model 56

A standard 5-conductor MIDI-style cable
is used to connect the Model 55 to the
Model 56; a cable is included with your
system. Just connect the cable between
the female 5-pin DIN-type connectors on
the back of the Model 55 and 56, and
you’re done.

Note: If you require a longer cable, be
certain to buy a MIDI cable that has all 5
pins wired. If they aren’t all connected, the
Model 56 will not operate. This is because
the Model 55 powers the Model 56 with
the pins that aren’t used for MIDI data.

For best performance, the cable that
connects the Model 55 with the Model 56
should be limited to 50 feet (15.3m).
Should you need to exceed this length,
refer to the Technical Notes section of
this guide for details on the cable
requirements.

For more information on MIDI, and using
controllers other than the Model 56, please
refer to Appendix A.

AC Mains Power

The Model 55 is internally configured to
operate from either 100, 120, or 220/240V,
50/60Hz. In most cases, units shipped to
North America are factory selected for
120V operation. Units bound for Japan are
selected for 100V, while our friends “down
under” and in Europe receive units set for
220/240V. Before connecting the Model 55
to mains power, check that it is configured
to match the local mains voltage. Look on
the back panel, adjacent to the power
entry connector, for the configured
voltage(s). Note than an incorrect configu­ration could seriously damage the unit.
Should it be necessary to change the

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