Studio Technologies 230 User Manual
User Guide
Issue 7, October 2008
This User Guide is applicable for serial numbers:
M230-00183 and later
and units upgraded with software version 1.04 and higher
Copyright © 2008 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50321-1008, Issue 7
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Table of Contents
Introduction ................................................................... 5
System Features ...........................................................
Installation and Setup ................................................... 12
Configuration ................................................................
Operation ...................................................................... 29
Advanced Operation ..................................................... 36
Technical Notes .............................................................
Specifications ................................................................
Appendix A .................................................................... 53
Block Diagram
6
18
37
52
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Issue 7, October 2008 Model 230 User Guide
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Introduction
What This User Guide Covers
This User Guide is designed to assist you
when installing, configuring, and using
the Model 230 Announcer’s Console. Additional background technical information
is also provided. A product block diagram
is included at the end of this guide.
System Overview
The Model 230 Announcer’s Console is
designed to serve as the audio control
“hub” for announcers, commentators, and
production personnel. The tabletop unit is
suited for numerous applications including
on-air television and radio broadcasting.
The Model 230 is compatible with essentially all broadcast and production audio
system environments. Standard connectors are used to interface microphone,
headphone, on-air, talkback, IFB, and
intercom signals.
Whether it’s the mic preamplifier, audio
switching, talkback signals, intercom interfacing, or headphone cue feed, superior
audio quality is maintained throughout. A
microprocessor provides the Model 230’s
logic power, allowing precise control of
the unit’s operation. With extensive flexibility built in, creating the desired operating
configuration is a simple matter. While the
operating features of the unit can be carefully tailored, the user is presented with an
easy-to-use set of controls and indicators.
A wide range of resources, great performance, and simplicity during use—these
are the hallmarks of the Model 230.
A truly next-generation product, exhaustive
research into the needs and desires of field
production personnel was integral to the
Model 230’s creation. Providing a veritable
“tool kit” of features, the unit supports a
wide variety of applications that include
on-air television and radio broadcasting,
stadium announcement, and simultaneous
Figure 1. Model 230 front panel
Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 5
Figure 2. Model 230 back panel
interpretation. In addition, with the unit’s
broad range of capabilities many other
specialized “behind-the-scenes” applications can also be implemented.
System Features
Microphone Input
A high-performance microphone preamplifier circuit provides low-noise/lowdistortion amplification over a 20 to 60
dB gain range. The gain is adjustable in
10 dB steps. The input is compatible with
balanced dynamic and condenser microphones. The microphone power source
is 48 volts nominal and meets the worldwide P48 phantom power standard. An
LED indicator serves as an aid for optimizing the preamplifier’s gain setting. The output of the microphone preamplifier is used
by the main output as well as being routed
to the compressor circuit that supports the
talkback functions.
Main Output
The Model 230 provides a main output that
is designed to serve as the on-air, stadium
announcement, or other primary audio
feed. Nominally –2 dBu, it is designed as
a fully professional interface with high
output capability, low distortion, and low
noise. The output circuitry features a
high-performance output transformer
expressly designed for professional
audio applications.
Talkback Functions
The talkback functions are intended
to provide personnel associated with
production trucks, control rooms, liveperformance, and sports venues with
talent-originated cue signals. The Model
230 contains two pushbutton switches that
control the talkback functions. Each button can be configured to allow talkback
audio to be routed to one of three locations: intercom channel 1, intercom channel 2, or a line-level talkback output. The
line-level talk-back output is transformercoupled with a +4 dBu nominal signal
level. It contains resistors in series with
the output connector, allowing line-level
talkback outputs from multiple units to be
directly “summed.”
For non-on-air applications, special Model
230 features can be enabled by placing
the unit in one of two “production” modes.
These software-based modes allow the
main output to be used either as a “hot
Issue 7, October 2008 Model 230 User Guide
Page 6 Studio Technologies, Inc.
mic output” or as an additional talkback
output. These features make the unit even
more powerful when used in live-event
applications, such as serving as a master
console for an orchestra conductor or
production director.
With all the available talkback flexibility,
the exact needs of many specific applica
tions can easily be met. And, of course,
whatever configuration is implemented,
the audio quality will be excellent.
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Dynamic Range Control
To enhance the Model 230’s talkback
functions, a studio-quality compressor
circuit is provided to control the dynamic
range of the signal coming from the microphone preamplifier. Far from a simple
“clipper,” the circuit utilizes a sophisticated
laser-trimmed voltage-controlled-amplifier
(VCA) integrated circuit for quiet, lowdistortion level control. The signal from
the compressor is used by the talkback
functions. This ensures that talkback
audio signals remain clear and intelligible
under all real-world conditions. In addition, dynamic range control is especially
important when talkback signals are being
routed to intercom channels.
User Controls and Status
Indicators
Three pushbutton switches, four LED
indicators, and two rotary controls provide
the user with a clear, easy-to-use interface.
One pushbutton switch controls the status
of the main output. This is the audio output intended for on-air, announcement,
or other primary uses. Two LEDs display
the on/off status of the main output. Two
additional pushbutton switches control the
status of the talkback functions. These are
the audio cue signals used to communicate with producers, directors, “spotters,”
or other behind-the-scenes production
personnel. A status LED is associated with
each talkback button. Two rotary controls
allow the user to adjust the level of the
headphone output.
Flexibility
A large part of the Model 230’s unique
power is the ability to configure the
operation of the main output and talkback
functions. To meet the needs of the many
specific broadcast and production applications, a variety of button operating
modes is available. The main output
button can be selected to operate from
among four modes. In the “push-to-mute”
mode the button performs a momentary mute of the main output. In this way
a “cough” button function is created,
something typically required for television
sports broadcasting. In the “push-to-talk”
mode the button provides a momentary
active function for the main output. This
mode would be appropriate for applications such as stadium announcement. An
alternate action “latching” configuration
allows the button to enable or disable the
main output as desired. This is useful in
radio broadcasting, announce-booth, or
voice-over applications. The fourth mode
provides a hybrid function, supporting
both push-to-talk and tap-to-enable/tap-todisable operation. This operation is similar
to that found in many broadcast intercom
system user stations.
The two buttons associated with the talkback functions can be configured to operate from either of two modes. One of the
modes supports a “push-to-talk” function.
This is typically used for on-air broadcast
applications. The other mode provides a
hybrid function, the operation of which is
discussed in the previous paragraph. The
hybrid mode is especially useful when the
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Model 230 is used in a production-support
application.
The main button mode configures how the
main output, when it is in the “latched” on
state, responds to talkback activity. One
choice momentarily turns off the main
output when talkback is active, returning
the main output to the on state when the
talkback function has ended. The other
choice “unlatches” the main output in
response to a talkback function.
For application flexibility, two line-level
audio sources can be connected to the
Model 230. Possible signal sources
include off-air receivers, wireless IFB
systems, and audio consoles. The connected signals can be from two independent sources, or could be from a stereo
audio feed such as would be associated
with a broadcast music event. Two level
trim potentiometers, located on the bottom
of the unit, allow signals with wide nominal
audio levels to be cleanly interfaced.
IFB Input
A broadcast-standard “wet” (DC with
audio) IFB circuit can be directly connected to the Model 230’s IFB input.
Originated by sources such as the RTS™
4000-series IFB system or IFB interface
devices from Studio Technologies, the
connected IFB circuit can provide DC
power to operate the Model 230 as well
as two channels of cue audio.
Cue Sources
The Model 230 supports the connection
of up to six audio sources, each of which
can be selected for routing to the stereo
headphone output. The sources are IFB
channel 1, IFB channel 2, line input 1, line
input 2, intercom channel 1, and intercom
channel 2. Each source can be individually assigned to the left channel, right
channel, or both left and right. This allows
a wide variety of stereo and mono headphone mixes to be created.
The two audio signals associated with
the Model 230’s IFB input can be assigned to the headphone output. Originating
in production trailers or control rooms,
the IFB circuits typically provide DC
power and program-with-interrupt audio
on one channel and program-only audio
on the other.
Audio signals associated with a single-
or dual-channel intercom system can
be routed to the headphone output. The
Model 230’s intercom interface is compatible with standard party-line intercom
systems from manufacturers such as RTS
and Clear-Com®.
Headphone Output
Two rotary controls are provided for user
adjustment of the headphone output
levels. For application flexibility the actual
function of the two “pots” is configurable.
For traditional on-air sports applications
they can be selected to the dual level
control mode which provides independent
control of the left and right channel volume. For use with stereo cue signals, or to
support user preference, the level/balance
mode can be selected. In this mode one
control adjusts the overall level of both
the left and right channels, while the other
allows adjustment of the left/right level
balance. To help minimize the chance of
broadcast cues being missed, both level
control modes can be configured so that a
minimum headphone output level is maintained. Alternately, the headphone output
can be set to fully mute when the controls
are at their minimum position.
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A headphone control reverse mode is
provided specifically for on-air television
applications where a headset with boom
microphone is used. The reverse mode
ensures that no matter which headset orientation is used by the talent, the controls
will always work intuitively. This results in
a comfortable work environment, allowing the left control to impact the level to
the talent’s left ear while the right control
impacts the right.
Provision has been made to support applications where a monaural cue feed
is desired. A configuration switch allows
the summing (combining) of the selected
left and right headphone sources. In addition to creating a dual-channel mono
output it also allows the level controls
to be configured as a simple 2-channel
mixer. For applications where a single
“muff” headset or IFB-type earpiece is
connected, another configuration switch
can be used to disable the headphone
output’s right channel.
The headphone output is optimized to
meet the needs of contemporary headphones and headsets. Specifically, the
output circuits act as voltage, rather than
power, drivers. In this configuration they
can provide high output levels with very
low distortion and noise, along with minimal current consumption. The output circuits are configured to safely drive stereo
or mono loads. This ensures that all types
of headphones, headsets, and earpieces
can be directly connected.
Intercom Interface
Of special note is the Model 230’s sophisticated intercom interface. It’s designed
to work correctly with industry-standard
single- and dual-channel party-line intercom systems, including those from RTS
and Clear-Com. An intercom line connected to the Model 230 can serve three
functions: providing cue audio signals to
the headphone output, allowing talkback
audio to be sent to intercom users, and as
a Model 230 power source. Audio signals
present on the single- or dual-channel
intercom line can be flexibly routed to the
headphone output. Talkback audio can
be sent to either or both intercom channels. Trim potentiometers, located on the
bottom of the unit, allow adjustment of the
talkback-to-intercom null (“sidetone”) level.
Other announcer console products can
exhibit talkback-to-intercom-related audio
oscillations (“squeals”) that end up in
the headphone output. A special Model
230 feature ensures that this will never
occur. This is accomplished by means
of a special “auto-terminate” circuit that
becomes active whenever an intercom
line is not connected to the Model 230.
Active Sidetone Function
The Model 230 includes a unique active
sidetone function that’s available whenever
the unit is configured for one of the two
production modes. By routing audio from
the microphone input to the headphone
output a user confidence (“sidetone”)
signal is provided. This allows a user to
always hear what they are saying, a critical
requirement for effective communications.
The word “active” is part of the function’s
name because it involves active circuitry,
under software control, to achieve excellent
audio performance. The sidetone level is
dynamically configurable, allowing the user
to adjust the level as required.
Audio Quality and Protection
The Model 230’s circuitry is carefully
tailored to provide excellent audio performance. Professional-quality components
Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 9
are featured throughout. For reliability all
audio routing is performed using solidstate devices under microcontroller direction. In all critical audio paths, “clickless”
electronic switches provide noise-free
control. All audio inputs and outputs make
extensive use of protection components.
This limits the chance of damage from
ESD and other undesirable, yet real-world,
hazards.
Power Sources
The Model 230 can derive its operating
power from an IFB circuit, an intercom
line, or an external 24 volt DC source. For
redundancy, all three power sources can
be connected simultaneously. An internal
switch-mode power supply ensures that
all Model 230 features are available, including phantom power, when the unit
is powered by any of the three sources.
The Model 230 is compatible with IFB
circuits provided by most standard broadcast systems. However, maximum performance can often be obtained by using the
IFB interface devices available from Studio
Technologies. Single-channel and fourchannel units are available, each providing
high-quality audio along with an excellent source of DC power. They’re directly
compatible with most matrix intercom systems, as well as standard line-level audio
signals. Refer to the Studio Technologies
website for details.
Auxiliary Relay
Model 230 resources include a generalpurpose relay, allowing specialized configurations to be created. Under software
control, the relay can be configured to follow the state of the main output, talkback
1, or talkback 2 buttons. Taking advantage
of the back-panel locations provided for
additional XLR-type connectors, a technician may easily implement a variety of
functions such as an “on-air” indicator or
performing loudspeaker muting during
talkback. Special configuration modes are
even included to allow direct control of the
relay using the talkback 1 or talkback 2
buttons without impacting any of the unit’s
audio signals.
Configuration
Model 230 configurations are made using
a number of DIP-type switches and four
trim potentiometers. One 8-position switch
array is used to set the gain of the microphone preamplifier, the on/off status of
phantom power, and control of the headphone output modes. A 12-position switch
array configures which of the six cue
audio sources are routed to the headphone outputs. Two 8-position switch
arrays communicate the desired operating modes to the microprocessor. Two rotary trim pots are used to adjust the input
sensitivity of the line inputs. Two additional
rotary trim pots are provided to adjust the
“sidetone” level for the intercom interface’s talkback functions. All switches and
trim pots are accessible via the bottom of
the Model 230’s enclosure; the unit does
not have to be disassembled. Changes
made to any of the configuration parameters become active immediately. To prevent access to the configuration controls a
security panel, included with each unit, is
attached to the bottom of the enclosure.
Connectors
The Model 230 uses standard connectors
throughout. The microphone input, line
inputs, IFB input, and intercom interface
functions use 3-pin female XLR-type connectors. The main output and line-level
talkback output functions use 3-pin male
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XLRs. The headphone output utilizes a
¼-inch 3-conductor jack. The external
source of 24 volt DC power is connected
by way of a 2.1 x 5.5 mm “locking” coaxial
power jack.
Additional Connector Locations
In the world of broadcast and production audio it’s fair to say that applications
vary widely. To this end, up to three additional XLR-type connectors can be easily
mounted into the Model 230’s back panel.
Multiple 3-position “headers” located on
the Model 230’s circuit board provide
technician-access to literally every input
and output connection. Using a factoryavailable interface cable kit, these allow
a Model 230 to be optimized to meet the
exact needs of specific applications. For
example, some applications may prefer
to use a multi-pin XLR-type connector to
interface with a headset. This could be
easily accomplished by adding the appropriate 5-, 6-, or 7-pin XLR-type connector
and making a few simple connections.
Other applications may benefit from having “mult” or “loop-through” connections,
something easily incorporated into a
Model 230.
Options
The Model 230’s standard resources are
more than sufficient to directly support a
large number of applications. But in the “real
world” of audio and intercommunications
special needs always seem to arise. To that
end, Studio Technologies offers a number of
option cards. In addition to passive or active
components, each card contains an integral
connector, allowing simple installation into
a spare connector location on the Model
230’s back panel. For interest, the resources
provided by some of these option cards are
worth describing.
• The direct microphone output card pro
vides access to the dynamic or condenser
microphone that is connected to the
Model 230’s mic input. Passive components, along with the auxiliary relay contact, create a “click-free” microphone-level
audio signal.
• The line output card allows the Model 230
to provide a second line-level talkback
output.
• The remote switch input card uses a 4-pin
XLR connector to provide access to the
Model 230’s remote switch inputs.
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Multi-Pin Headset Connectors
As previously mentioned, some broadcast
applications use headsets that interface
using a multi-pin connector. In most cases
these connectors are 6- or 7-pin male
XLR-type wired to an industry-standard
pin out scheme. Studio Technologies
offers headset connector assemblies that
allow fast and painless installation into
a spare connector location in the Model
230’s back panel. Details about these
optional assemblies are available on the
Studio Technologies website.
• The tally/remote switch input card pro
vides a current-limited DC voltage that
serves as a main output status signal.
It also provides a remote switch input
connection.
Other general purpose option cards provide
3-pin XLR, 4-pin XLR, and 8-pin EtherCon®
connectors. With the range of option cards
available it’s hard to imagine an application
that can’t be served. But you’re welcome
to try to “stump the chumps” in the Studio
Technologies technical support department!
But first please check the complete list of
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the available option cards listed on the
Studio Technologies website.
Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 11
200-Series Announcer
Console Products
The Model 230 is just one in a series of
announcer console products available
from Studio Technologies. The Model 230
was designed to support a variety of applications where a wide range of features
and flexibility is required. For applications
whose requirements are more limited in
scope, other products in the 200-series
should be reviewed. Complete information
is available on the Studio Technologies
website.
Installation and
Microphone Input
The Model 230 is compatible with
balanced dynamic and condenser microphones. Depending on the application,
the microphone may be part of a headset,
or be an independent handheld or standmounted model. The Model 230’s 48 volt
nominal power source will support essentially all phantom-powered microphones.
The quality of the Model 230’s microphone
preamplifier and associated circuitry is
such that special applications may benefit
from using “high-end” microphones. If
selected appropriately, models from manufacturers such as AKG, Beyerdynamic,
Neumann, Sennheiser, and Shure will perform very well in Model 230 applications.
Setup
In this section interconnections will be
made using the input and output connectors located on the Model 230’s back
panel. Microphone, IFB, line-level audio
source, intercom, main output, and linelevel talkback output signals are interfaced
by way of 3-pin XLR-type connectors. A
¼-inch 3-conductor phone jack is provided for the headphone output. A 2.1 x 5.5
mm coaxial jack allows connection of an
external 24 volt DC power source.
System Components
Included in the shipping carton are the following: Model 230 Announcer’s Console,
user guide, button label sheet, and 24 volt
DC power supply. For units shipped to
destinations in Japan and North America
the power supply will have a nominal AC
mains input of 120 volts. For all other destinations a power supply compatible with
220/240 volt AC mains will be included.
Microphone interconnection is made by
way of a 3-pin female XLR-type connector which is located on the Model 230’s
back panel. The mating connector (male)
should be wired so that pin 2 is signal
high (+ or hot), pin 3 is signal low (– or
cold), and pin 1 is shield. It’s possible that
an unbalanced microphone will also work
correctly. In this case, the mating connector (male) should be wired so that pin 2
is signal high (+ or hot), and signal
common/shield is connected to both
pins 1 and 3.
The Model 230 is not compatible with
unbalanced “electret”-type microphones
that require a source of low-voltage DC
for operation. These microphones, sometimes found in low-cost headsets, are
not generally suitable for on-air or other
demanding applications.
As of the writing date of this user guide,
the Sennheiser HMD25 headset is very
popular for on-air sports broadcasting
use. A fine product, it works very well with
the Model 230. Note that adding the suffix
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Page 12 Studio Technologies, Inc.
“-XQ” to the headset’s part number
(HMD25-XQ) specifies a 3-pin male XLRtype connector for the dynamic microphone and a ¼-inch 3-conductor plug for
the stereo headphones. This configuration is very useful, allowing the headset
to work directly “out of the box” with the
Model 230.
If the writer may digress for a moment to
recount a story… an audio dealer once
shared a secret with me concerning headsets. He loved selling the “lower-end” (less
expensive) models of name-brand headsets, which he did by the veritable “boatload.” Why? Because these usually broke
soon after going into service! He knew
that on a regular basis he’d receive orders
for more of them. Had these users, from
the beginning, purchased only premiumquality headsets, their total cost of ownership would have been much less. Enough
said…
Headphone Output
The Model 230’s headphone output is
compatible with stereo or mono headphones, headsets, or earpieces. Connecting devices with a nominal impedance
of 100 ohms or greater is preferred. This
shouldn’t be an issue as essentially all
contemporary devices already meet this
condition.
Devices are connected to the headphone
output by way of a ¼-inch 3-conductor
phone jack located on the Model 230’s
back panel. As is standard for stereo
headphones, the left channel is connected
to the “tip” lead of the ¼-inch headphone
jack. The right channel is connected to
the “ring” lead of the jack. Common
for both channels is connected to the
“sleeve” lead.
Devices with ¼-inch 2-conductor “mono”
plugs can also be used with the Model
230’s headphone output. In this arrangement only the tip lead (left channel) will
be active. The 2-conductor plug will physically connect (“short”) the ring lead (right
channel) to the sleeve lead (common).
Technically this won’t damage the circuitry associated with the right-channel
headphone output. (51 ohm protection
resistors are electrically in series with the
headphone output circuits.) However,
energy will be wasted if an audio signal
coming out of the right channel goes into
a “dead” short. There is a simple means
of eliminating this issue; a configuration
setting allows the right channel of the
headphone output to be disabled. Refer
to the Configuration section of this user
guide for details.
Main Output
The main output is intended to be the “onair” signal that connects to the input of an
audio console. The output is transformer
balanced with a nominal signal level of
–2 dBu. The actual level will depend on
the gain setting of the microphone preamplifier, sensitivity of the microphone,
and how loudly the talent speaks into
the microphone. The transformer used
in the main output is intended for professional broadcast applications. It has a low
source impedance and can drive lengthy
cable runs with no difficulty. It is capable
of driving 600 ohm loads but performs
best with loads of 2 k ohms or greater.
(This should not prove to be an issue as
virtually all contemporary audio equipment
has a relatively high input impedance.)
As the secondary winding of the output
transformer connects directly to the main
output connector, care should be taken
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Studio Technologies, Inc. Page 13
so that DC voltage is never present on the
interconnecting cable.
The main output is interfaced by means of
a 3-pin male XLR-type connector located
on the Model 230’s back panel. The interconnecting cable’s mating connector
(female) should be wired so that signal
high (+ or hot) is on pin 2 and signal low
(– or cold) is on pin 3. The cable’s shield
can be connected to pin 1, but it will have
no function. To limit the chance of grounding interaction between the Model 230 and
connected equipment, pin 1 on the main
output’s connector is isolated from any
point in the Model 230. The fact that pin 1
“floats” will minimize the chance of hums,
noises, or buzzes being present on the
equipment connected to the main output.
Line-Level Talkback Output
The line-level talkback output is intended to
be connected to control rooms, production
trailers, or other locations where talentoriginated voice cues are required. The output is transformer balanced with a nominal
level of +4 dBu. To enhance talkback audio
quality, a compressor circuit controls the
dynamic range of the signal coming from
the microphone preamplifier.
For protection against accidental connec
tion to cables that have DC power present,
the line-level talkback output is capacitor
coupled. In series with the talkback output
leads are 300 ohm resistors, making the
effective output impedance approximately
600 ohms. These resistors create a passive summing network, allowing talkback
outputs on multiple Model 230 units to be
connected together.
The line-level talkback output is connected
by way of a 3-pin male XLR-type connector which is located on the Model 230’s
back panel. The mating connector (female)
-
should be prepared so that signal high (+
or hot) is expected on pin 2. Signal low
(– or cold) should be expected on pin 3.
The cables’ shields can be connected to
pin 1. But, like the main output, in order
to minimize the chance that groundinteraction problems will arise, pin 1 on
the line-level talkback output connector is
isolated from the Model 230’s chassis and
circuitry. By making pin 1 “float,” an oftenfeared “ground loop” problem shouldn’t
arise.
The line-level talkback output is intended
to drive lengthy cable runs that are
frequently part of a remote broadcast
application. While the output circuitry is
not intended to be “on-air” quality, overall audio performance should be very
good. Devices connected to the line-level
talkback output can range from amplified loudspeakers to analog inputs on
intercom systems, and input channels
associated with audio consoles. Connecting the output to devices that allow easy
control of the signal level can be helpful.
For example, connecting to a spare input
module on an audio console provides
the flexibility to add gain or attenuate as
required. A dedicated talkback-associated
output on the audio console can then be
connected to the final destination(s).
As previously mentioned, the line-level
talkback output on multiple Model 230
units can be directly connected together.
Using a simple “Y” or “W” cable, this
passive summing (adding together) of
talkback signals allows one audio cable
to serve as a master talkback path. A side
effect from using this passive summing
technique is that signal attenuation will
occur. The audio quality won’t suffer, but
an audio “pad” is created. If two line-level
talkback outputs are connected together,
Issue 7, October 2008 Model 230 User Guide
Page 14 Studio Technologies, Inc.
a signal attenuation of 6 dB can be expected. Connecting three outputs together
will result in 9.5 dB of attenuation. And
four outputs “multed” together will lead to
12 dB of attenuation. In most cases this attenuation won’t pose a problem. Typically
a device that receives the talkback signal,
such as an amplified loudspeaker, will
have an adjustable input sensitivity.
IFB Input
The Model 230’s IFB input is designed
to directly connect with “wet” (DC-biased)
IFB circuits. These circuits provide DC
power and one or two channels of audio
over a standard 3-conductor microphonestyle cable. Typically, the IFB circuit’s
interface connector is a 3-pin male XLRtype wired so that common is on pin 1,
DC with channel 1 audio is on pin 2, and
channel 2 audio is on pin 3. Some IFB
circuits may only have one audio channel.
In this case, audio will generally be on pin
3 with pin 2 providing only DC power.
The power supplied by an IFB circuit,
normally in the range of 28 to 32 volts DC,
is usually sufficient to operate the Model
230’s circuitry. The acceptable input range
is 24 to 32 volts, with a required current
of 125 milliamperes. Note that the specified input voltage is given when measured
directly at the Model 230’s IFB input connector, not at the source of the IFB circuit.
The one or two audio signals provided
by the IFB circuit can serve as the audio
sources for the headphone outputs.
In North American field and in-studio
broadcast applications it is common to
find RTS 4000-series IFB equipment being used to provide the IFB circuits. The
Model 230 can be directly connected to,
and function correctly with, one of these
circuits. For reliable operation, especially
when using lengthy cable runs, it’s strongly recommended that no other device be
connected to a 4000-series IFB circuit that
is specified for connection to a Model 230.
This requirement is due to the currentlimited DC source that is supplied by the
4010 IFB Controller.
With 4000-series IFB circuits channel 1
(XLR pin 2) provides program audio
that is “interrupted” with cue signals.
This channel is sometimes referred to
as “program-with-interrupt.” It’s important
to note that the program audio source
fully mutes whenever directors or producers are communicating with on-air talent.
Channel 2 (XLR pin 3) of the IFB circuit
provides a “program-only” audio feed. It
is never interrupted with cue signals.
While the Model 230’s IFB input was
designed for connection to a “wet” IFB
circuit, it’s also possible to connect linelevel audio sources. Please refer to the
Technical Notes section of this user guide
for details.
Line Inputs
The Model 230 allows two line-level audio
sources to be connected. These sources
can be individually routed to the leftchannel, right-channel, or both the leftand right-channel headphone outputs.
The inputs are balanced, transformercoupled with a nominal impedance of 10 k
ohms. Capacitors, in series with the transformer’s input leads, prevent a DC voltage
present on a connected source from
impacting performance. The line inputs
are compatible with signals that have a
nominal level of –12 dBV to +6 dBu. Two
trim potentiometers, located on the bottom of the Model 230’s enclosure, allow
signals over this wide nominal level range
to be effectively utilized. Audio sources are
Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 15
connected to the line inputs by way of
3-pin female XLR-type connectors which
are located on the unit’s back panel.
Prepare the mating connectors (males) so
that pin 2 is signal high (+ or hot), pin 3
is low (– or cold), and pin 1 is shield. If
connecting a source in this manner results
in hum or noise, it’s possible that removing the shield connection from pin 1 can
eliminate the issue. With an unbalanced
source connect pin 2 to signal high (+
or hot) and both pins 1 and 3 to shield. If
connecting an unbalanced source in this
manner results in hum or noise, connect
pin 2 to high (+ or hot) and pin 3 to shield;
leave pin 1 unterminated.
Intercom Interface
The Model 230’s intercom interface is
designed to directly connect with standard
single- and dual-channel party-line intercom lines. The one or two audio signals
provided by the intercom line can serve
as audio sources for the headphone
outputs. Each signal can be individually
assigned to the left channel, the right
channel, or both the left and right channels. The Model 230 can be configured
to send talkback audio to either or both
of the intercom channels. In addition, the
intercom line can also provide the DC
power required to operate the Model 230’s
circuitry.
The intercom line is connected to the
Model 230 by way of a 3-pin female XLRtype connector which is located on the
back panel. The mating connector (male)
should be wired so that common is on
pin 1, DC with channel 1 audio is on pin
2, and channel 2 audio is on pin 3. With
single-channel intercom lines common is
on pin 1, DC power is on pin 2, and audio
is connected to pin 3.
The Model 230’s intercom interface is
directly compatible with broadcast and
production party-line intercom lines associated with systems from manufactures
such as RTS and Clear-Com. Intercom
lines associated with other systems
should be equally compatible. RTS TW
series systems are normally interfaced
using 3-pin XLR-type connectors. These
connectors are wired with common on
pin 1, DC power and channel 1 audio on
pin 2, and channel 2 audio on pin 3. With
many Clear-Com systems, common is on
pin 1, DC power is provided on pin 2, and
audio is provided on pin 3.
The DC power supplied by the connected
intercom line is generally sufficient to
operate the Model 230’s circuitry. The
acceptable input range is 24 to 32 volts,
with a required current of 125 milliamperes. Note that the specified input voltage is given when measured directly at
the Model 230’s intercom connector, not
at the source of the intercom line.
External Power Input
An external source of 24 volt DC power
can be connected to the Model 230 by
way of a 2.1 x 5.5 mm coaxial power jack
which is located on the back panel of
the unit. The center pin of the jack is the
positive (+) connection. While the requirement for the external source is nominally
24 volts, correct operation will take place
over a 20 to 30 volt range. The Model 230
requires 90 milliamperes at 24 volts DC
for correct operation. Included with each
Model 230 is a 24 volt DC external power
supply. The power supply’s DC output
cable has been terminated with a Switchcraft® S760K coaxial power plug. This
“locking” type of plug correctly mates
with the Model 230’s 24 Vdc input jack.
The locking feature is important, allowing
Issue 7, October 2008 Model 230 User Guide
Page 16 Studio Technologies, Inc.
the external power source to be securely
attached to the Model 230.
As previously discussed in this user guide,
an IFB circuit or intercom line connected
to the Model 230 can serve as the unit’s
power source. Alternately, an external 24
volt DC source can be connected. For
redundancy, the IFB circuit, the intercom
line, and the external source can be connected at the same time. If one of them
becomes inoperative, one of the remaining sources can provide all Model 230
power.
The Model 230’s circuitry establishes the
priority in which the unit draws its operating power. If an external source of 24
volt DC power is connected, it will always
serve as the primary source. This minimizes the impact that the unit’s power
draw could have on a connected IFB circuit or intercom line. If no external source
of 24 volt DC is connected and both an
IFB circuit and an intercom line is connected, power will be drawn only from the
intercom line. This is because intercom
lines, by design, are better able to supply
power to devices such as the Model 230.
Multiple devices, such as intercom belt
packs, are expected to be connected to,
and powered by, a single intercom line.
IFB circuits are quite different, typically designed to only supply a limited amount of
energy. This limitation can be compounded by the fact that IFB circuits are often
distributed using very long cable “runs.”
So in conclusion, the Model 230’s power
draw priority was established so as to
minimize the chance that IFB circuit
performance would be impaired. And,
of course, no matter which source is providing power, audio signals from the IFB
circuit and intercom line can still serve
as headphone output audio sources.
Pushbutton Labeling
The three pushbutton switches used in
the Model 230 were selected for several
reasons. Foremost was the fact that they
are highly reliable, using gold-plated contacts for long life in less-than-ideal environments. A second reason was that applying
customized labels to the button caps
would be very simple. The labels, text
printed on clear material, are placed under
the clear caps on the top of the buttons.
From the factory the left button is labeled
COUGH, the center button is labeled
TALKBACK 1, and the right button is
labeled TALKBACK 2. This was selected
to be appropriate for many on-air applications in English-speaking locations. But
it’s expected that these may need to be
changed to meet the needs of specific
applications.
As a “head start” for some applications,
a clear sheet with a number of commonly
used button designations printed on it
is included in the shipping carton. These
were created at the factory using a standard personal computer graphics program
and laser printed onto 3M CG3300 transparency film. The desired button labels
can be cut out with a pair of scissors, following the printed guide lines that indicate
the required size.
The clear lens on top of each button cap
can be removed with a fingernail or small
screwdriver. Be certain not to scratch the
button if a screwdriver or other small tool
is used. The clear label can be removed
and replaced. The button cap is then
snapped back into the top of the button
housing using finger-pressure only. No
tool is required to replace the button cap.
If you need to make your own labels the
process is quite simple. Use a personal
Model 230 User Guide Issue 7, October 2008
Studio Technologies, Inc. Page 17
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