Studio Technologies Model 211 User manual

Copyright © 2015 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
User Guide
Issue 1, December 2015
This User Guide is applicable for serial numbers:
M211-00151 and later
50616-1215, Issue 1

This page intentionally left blank.

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 3
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
System Features .......................................................... 5
Installation and Setup ................................................... 9
Configuration ................................................................ 13
Operation ...................................................................... 21
Technical Notes ............................................................ 24
Specifications ............................................................... 29
Appendix A ................................................................... 30
Appendix B ................................................................... 31
Block Diagram

Issue 1, December 2015 Model 211 User Guide
Page 4 Studio Technologies, Inc.
Revision History
Issue 1, December 2015:
1. Initial release.

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 5
Introduction
What This User Guide Covers
This User Guide is designed to assist
you when installing, configuring, and us-
ing Model 211 Announcer’s Consoles with
serial numbers 00151 and later. Additional
background technical information is also
provided. A product block diagram is includ-
ed at the end of this guide.
System Overview
The Model 211 Announcer’s Console is
designed to serve as the audio control
center for announcers, commentators, and
production talent. The tabletop unit is suited
for numerous applications including on-air
television sports broadcasting. The Model
211 integrates all on-air, talkback, and cue
audio signal routing into one compact sys-
tem. Ease of use, configuration flexibility,
and sonic excellence are some of the unit’s
highlights.
The Model 211 is compatible with many
broadcast and audio system environments.
Standard connectors are used to interface
microphone, headphone, talkback, and
talent cue signals. Whether it’s microphone
switching, talkback output, or headphone
cue feed, superior audio quality is main-
tained. A microprocessor provides the
Model 211’s logic power, allowing exact-
ing control of the unit’s operation. A range
of configuration choices allow the desired
operating parameters to be easily selected.
While flexible, the user is presented with an
easy-to-use set of controls and indicators.
A truly next-generation product, extensive
research into the needs and desires of field
production personnel was integral to the
Model 211’s creation. Target applications
include on-air television, radio, streaming,
and production applications. Specialized
features are included to allow the Model 211
to be used in a variety of other audio appli-
cations. These include stadium announce-
ment and voice-over/narration booths.
System Features
Microphone Input
A high-performance microphone preampli-
fier circuit provides low-noise/low-distortion
amplification over a 20 to 60 dB gain range.
The gain is adjustable in 10 dB steps. The
input is compatible with balanced dynamic
Figure 1. Model 211 front and back views

Issue 1, December 2015 Model 211 User Guide
Page 6 Studio Technologies, Inc.
or condenser-type microphones. The
microphone power source meets the
worldwide P48 phantom power standard.
The preamplifier’s gain can also be set
for 0 dB, allowing a line-level audio signal
to be connected. This could prove useful
in special applications such as when an
external preamp or mic processor is being
used. An LED indicator serves as an aid
for optimizing the setting of the preampli-
fier’s gain. 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 function.
Main and Talkback Outputs
The Model 211 provides one main and
one talkback output. The main output is
designed to serve as the on-air, stadium
announcement, or other primary audio
feed. With a nominal level of –2 dBu, it is
designed as a fully professional interface
with high output capability, low distortion,
and low noise. It features a high-quality
transformer expressly designed for driving
long broadcast cable runs. The talkback
output is intended to provide production
trucks, control rooms, or support person-
nel with a talent-originated cue signal. The
talkback output is transformer-coupled
with a +4 dBu nominal signal level. It
contains resistors in series with its output
connections, allowing the talkback output
from multiple units to be directly summed
(combined).
For non-on-air applications, a specialMod-
el 211 feature can be enabled, placing the
unit in a “production” mode. This allows the
main output to be used as a second talk-
back output. In this configuration the unit
can be even more powerful when used in
a live-event application, such as serving as
a master console for a production director.
Dynamic Range Control
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, low-distortion
level control. The signal from the compres-
sor is always used by the talkback output.
In addition, the audio source for the main
output can be selected to be either the out-
put of the microphone preamplifier or the
output of the compressor. While possibly
inappropriate for major on-air situations,
having dynamic range control of the main
output can offer increased effectiveness
for many applications. These could include
stadium announcement positions, sports
events using non-professional on-air talent,
and situations where cable crosstalk is of
concern.
User Controls and Status
Indicators
Two pushbutton switches, three LED indi-
cators, 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 out-
put intended for on-air, announcement, or
other primary uses. Two LEDs display the
on/off status of the main output. A sec-
ond pushbutton switch controls the status
of the talkback output. This is the audio
output used to communicate with produc-
ers, directors, spotters, or other behind-
the-scenes production personnel. A status
LED is associated with the talkback button.
Two rotary controls allow the user to adjust
the level of the headphone output.

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Flexibility
A large part of the Model 211’s unique
power is the ability to configure the op-
eration of the main output and talkback
functions. To meet the needs of the many
specific broadcast and production applica-
tions, 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 broadcast-
ing. 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 sta-
dium announcement. An alternate action
“latching” configuration allows the button
to enable or disable the main output as
desired. This is useful in radio broadcast-
ing, announce-booth, or voice-over appli-
cations. The fourth mode provides a hybrid
function, supporting both push-to-talk and
tap-to-enable/tap-to-disable operation. This
operation is similar to that found in many
broadcast intercom system user stations.
The button associated with the talkback
function 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
Model 211 is used in a production-support
application.
Cue Sources
Two line-level audio sources can also be
connected to the Model 211. Possible sig-
nal sources include audio consoles, matrix
intercom systems, and off-air receivers.
The connected signals can be from two
independent sources or could be a stereo
audio feed such as would be associated
with a broadcast music event. Two trim
potentiometers, located on the bottom of
the unit, allow signals with wide nominal
audio levels to be cleanly interfaced. Each
source can be individually assigned to the
left channel, right channel, or both left and
right channels of the headphone output.
This allows a wide variety of stereo and
mono headphone mixes to be created.
Using the optional IFB Input Card Kit
broadcast-standard 2-channel powered
(“wet”) IFB circuits can also be connected
to the Model 211. In this way an IFB (“in-
terruptable foldback”) audio signal can
be used as a source of headphone cue
audio signals. (But note that the connected
IFB circuit will not be able to power the
Model 211; only the audio signals will be
interfaced!) The two audio signals associ-
ated with the IFB input can be assigned
to either or both of the headphone output
channels. Originating in production trailers,
control rooms, or remote locations, an IFB
source typically provides DC power and
program-with-interrupt audio on one chan-
nel and program-only audio on the other.
The IFB Input Card Kit also allows direct
connection to single- and dual-channel
party-line (PL) intercom circuits. This can
be useful when applications will benefit
from intercom audio channels being used
for headphone cue signals. But be aware
that no talkback into the PL circuits is pos-
sible, nor is it possible to power the Model
211 from the party-line circuit.

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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-channel
(“level/level”) mode which provides inde-
pendent control of the left- and right-
channel volume. For use with dual-channel
cue signals, or to support user preference,
the stereo (“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 adjust-
ment 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 mini-
mum headphone output level is main-
tained. Alternately, the headphone output
can be set to fully mute when the controls
are at their minimum position.
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 ad-
dition to creating a dual-channel mono
output it also allows the level controls to be
configured as a simple 2-channel mixer.
The headphone output was designed to
meet the needs of contemporary head-
phones 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 mini-
mal current consumption. The output cir-
cuits are configured to safely drive stereo
or mono loads. This ensures that all types
of headphones, headsets, and earpieces
can be directly connected.
Audio Quality and Protection
The Model 211’s circuitry is carefully
tailored to provide excellent audio perfor-
mance. Professional-quality components
are featured throughout. For reliability all
audio routing is performed using solid-
state devices. In all critical audio paths,
“clickless” electronic switches provide
noise-free control. All audio inputs and
outputs make extensive use of protec-
tion components. This limits the chance of
damage from ESD and other undesirable,
yet real-world, hazards.
Power Source
The Model 211 derives its operating pow-
er from an external nominal 24 volt DC
source. Internal switch-mode power supply
circuitry uses the incoming 24 volt source
to generate the various voltages required
by the Model 211’s circuitry, including
P48 phantom. A universal input/24 volt DC
external power supply is included
with each Model 211 unit.
Relay Contacts
The Model 211’s circuitry includes two
general-purpose relay contacts to allow
specialized configurations to be created.
Under software control, the form-A (nor-
mally open) solid-state relay contacts
follow the state of the main and talkback
output functions. Taking advantage of the
locations provided for additional XLR con-
nectors, a technician may easily implement
a variety of functions such as a mic active
indication, audio muting during talkback,
or audio insertion control.
Configuration
Model 211 configurations are made using
a number of DIP switches. One 8-position
switch assembly is used to set the gain of

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 9
the microphone preamplifier, the on/off sta-
tus of phantom power, and the headphone
stereo/mono mode. A second 8-position
switch assembly configures which of the
line-input and optional auxiliary input audio
sources are routed to the headphone
output. A third 8-position switch assem-
bly communicates the desired operating
modes to the microprocessor. All switches
are accessible via the bottom of the Model
211’s enclosure; the unit does not have to
be disassembled. Changes made to any
of the configuration parameters become
active immediately. To prevent unwanted
access to the configuration switches a
security plate, included with each unit, is
attached to the bottom of the enclosure.
Connectors
The Model 211 uses standard connectors
throughout. The microphone and line-level
inputs use 3-pin female XLR connectors.
The main and talkback outputs use 3-pin
male XLRs. A ¼-inch 3-conductor jack is
used for the headphone output. The ex-
ternal source of 24 volt DC power is con-
nected by way of a 2.1 x 5.5 mm “locking”
coaxial power jack.
In the world of broadcast and production
audio it’s fair to say that applications vary
widely. To this end, one or two additional
XLR connectors can easily be mounted
into the Model 211’s back panel. Multiple
3-position headers located on the Model
211’s circuit board provide technician ac-
cess to all input and output connections.
Using a factory-available interface cable
kit allows a Model 211 to be optimized to
meet the exact needs of specific applica-
tions. For example, some applications may
prefer to use a multi-pin XLR connector to
interface with a headset. This can easily be
accomplished by adding the appropriate
5-, 6-, or 7-pin XLR connector and mak-
ing a few simple connections. Other ap-
plications may benefit from having “mult”
or “loop-through” connections, something
easily incorporated into a Model 211.
An optional IFB input card, as previously
discussed, can also be mounted in one
of the spare XLR connector positions.
200-Series Announcer
Console Products
The Model 211 is just one in a series of
announcer console products available from
Studio Technologies. For applications that
require an alternate set of features the
other products in the 200-Series should
be reviewed. Complete information is avail-
able on the Studio Technologies website.
Installation and
Setup
In this section interconnections will be
made using the input and output con-
nectors located on the Model 211’s back
panel. Microphone, cue audio, main output,
and talkback output signals are interfaced
by way of 3-pin XLR 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 211 Announcer’s Console,
user guide, button label sheet, and 24 volt
DC power supply.

Issue 1, December 2015 Model 211 User Guide
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Microphone Input
The Model 211 is compatible with bal-
anced dynamic and condenser micro-
phones. Depending on the application,
the microphone may be part of a headset,
or be an independent handheld or stand-
mounted model. The Model 211’s P48
power source will support essentially all
phantom-powered microphones. The qual-
ity of the Model 211’s microphone pream-
plifier and associated circuitry is such that
special applications may benefit from using
“high-end” microphones. If selected appro-
priately, models from manufacturers such
as AKG, Beyerdynamic, DPA, Neumann,
Sennheiser, and Shure will perform very
well in Model 211 applications.
Microphone interconnection is made by
way of a 3-pin female XLR connector
which is located on the Model 211’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 unbal-
anced 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.
As of the writing date of this user guide,
the Sennheiser HMD 26 headset is very
popular for on-air sports broadcasting
use. A fine product, it works very well with
the Model 211. Note that adding the suf-
fix “-XQ” to the headset’s full part number
(HMD 26-600-XQ) specifies a 3-pin male
XLR connector for the dynamic micro-
phone 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 211.
If the writer may digress for a moment to
recount a story… an audio dealer once
shared a secret with me concerning head-
sets. 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 premium-quality headsets,
their total cost of ownership would have
been much less. Enough said…
Headphone Output
The Model 211’s headphone output is com-
patible 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 meet this condition.
Devices are connected to the headphone
output by way of a ¼-inch 3-conductor
phone jack located on the Model 211’s
back panel. As is standard for stereo head-
phones, 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 “monaural”
plugs can also be used with the Model 211’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 since 100
ohm protection resistors are electrically in
series with the headphone output circuits.

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 11
Main Output
The main output is intended to be the “on-
air” 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 preampli-
fier, sensitivity of the microphone, and how
loudly the talent speaks into the micro-
phone. The transformer used in the main
output is intended for professional broad-
cast applications. It has a low output im-
pedance 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 so that DC voltage is never present
on the interconnecting cable.
The main output is interfaced by means
of a 3-pin male XLR connector located on
the Model 211’s back panel. The intercon-
necting 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 con-
nected to pin 1, but it will have no function.
To limit the chance of grounding interaction
between the Model 211 and connected
equipment, pin 1 on the main output’s
connector is isolated from any point in the
Model 211. 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.
Talkback Output
The talkback output is intended for connec-
tion to control rooms, production trailers,
or other locations where talent- originated
voice cues are required. The talkback out-
put is transformer balanced with a nominal
level of +4 dBu. To enhance talkback audio
quality, the 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 talkback output is capacitor coupled.
Also in series with the talkback output con-
nections are 300 ohm resistors, making
the effective output impedance approxi-
mately 600 ohms. These resistors create
a passive summing network, allowing talk-
back outputs on multiple Model 211 units
to be connected together.
The talkback output is connected by way
of a 3-pin male XLR connector which is
located on the Model 211’s back panel.
A 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 cable’s
shield can be connected to pin 1. But, as
with the main output, in order to minimize
the chance that ground-interaction prob-
lems will arise, pin 1 of the talkback output
connector is isolated from the Model 211’s
chassis and circuitry. By making pin 1
“float,” the often-feared “ground loop”
problem shouldn’t arise.
The talkback output is intended to drive
lengthy cable runs that are frequently part
of a remote broadcast application. While
the talkback output circuitry is not intended
to be “on-air” quality, overall audio per-
formance should be very good. Devices
connected to the talkback output include
amplified loudspeakers, analog inputs on
intercom systems, and input channels as-
sociated with audio consoles. Connecting

Issue 1, December 2015 Model 211 User Guide
Page 12 Studio Technologies, Inc.
the talkback output to devices that allow
easy control of the signal level can be
helpful. For example, connecting to a spare
input channel on an audio console will pro-
vide the flexibility to add gain or attenuate
as required. A talkback-associated output
connection on the audio console can then
connect to the final destination(s).
As previously mentioned, the talkback
outputs on multiple Model 211 units can
be directly connected together. Using a
simple “Y” or “W” cable, this passive sum-
ming (adding together) of talkback signals
allows one audio cable to serve as a mas-
ter talkback path. A side effect when using
this passive summing technique is that sig-
nal attenuation will occur. The audio quality
won’t suffer appreciably, but an audio “pad”
is created. If two talkback outputs are
connected together, a signal attenuation
of 6 dB can be expected. Connecting three
talkback outputs together will result in
9.5 dB of attenuation. And four talkback
outputs “multed” together will lead to 12 dB
of attenuation. In most cases this attenua-
tion won’t pose a problem. Typically a de-
vice that receives the talkback signal, such
as an amplified loudspeaker, will have a
method of adjusting its input sensitivity.
Line Inputs
The Model 211 allows two line-level audio
sources to be connected. These sources
can be individually routed to the left chan-
nel, right channel, or both the left and right
channel of the headphone outputs. The
inputs are balanced, transformer-coupled
with a nominal impedance of 10 k ohms.
Capacitors, in series with the transformer’s
input leads, prevent a DC voltage pres-
ent on a connected source from impacting
performance. The line inputs are compat-
ible with signals that have a nominal level
of –12 dBV to +6 dBu. Two trim potentiom-
eters, located on the bottom of the Model
211’s enclosure, allow signals over this
wide nominal level range to be effectively
utilized. Audio sources are connected to
the line inputs by way of 3-pin female XLR
connectors which are located on the unit’s
back panel. Prepare the mating connec-
tors (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 pos-
sible 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 not terminated
DC Power Input
An external source of nominally 24 volt DC
power must be connected to the Model
211 by way of a 2.1 x 5.5 mm coaxial pow-
er jack which is located on the back panel
of the unit. The center pin of the jack is the
positive (+) connection. While the require-
ment for the external source is nominally
24 volts, correct operation will take place
over a 20 to 30 volt range. The Model 211
requires 70 milliamperes at 24 volts DC
for correct operation.
Included with each Model 211 is a 24 volt
DC external power supply. The power sup-
ply’s DC output cable has been terminated
with a Switchcraft® S760K coaxial power
plug. This “locking” type of plug correctly
mates with the Model 211’s 24 volt DC
input jack. The locking feature is important,
allowing the external power source to be
securely attached to the Model 211.

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 13
Pushbutton Labeling
The two pushbutton switches used in the
Model 211 were selected for several rea-
sons. Foremost was the fact that they are
highly reliable, using gold-plated contacts
for long life in less-than-ideal environ-
ments. 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 and the right button is labeled
TALKBACK. This was selected to be ap-
propriate for many on-air applications in
English-speaking locations. But it’s expect-
ed 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 English-language button designa-
tions printed on it is included in the ship-
ping carton. These were created at the
factory using a standard personal comput-
er graphics program and laser printed onto
3M CG3300 or equivalent transparency
film. The desired button labels can be cut
out with a pair of scissors or an X-ACTO®
knife 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 us-
ing 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
computer to create the desired text. The
finished label size should be 0.625-inches
(15.8 mm) square. The completed artwork
can then be printed on transparency film
sheets using a laser or inkjet printer. These
sheets are readily available from most of-
fice supply stores. A pair of scissors or an
X-ACTO knife will complete the task.
Configuration
For the Model 211 to support the needs
of specific applications a number of
operating parameters must be configured.
These include microphone preamplifier
gain, phantom power on/off, headphone
source selection, headphone stereo/mono
mode, and operating modes. Three
8-position DIP switch assemblies are
used to establish the desired configuration.
These switch assemblies are referred to
as SW1, SW2, and SW3, with individual
switches designated as SW1-1, SW1-2,
etc. The switch assemblies are accessed
through openings in the bottom of the
Model 211’s enclosure. The enclosure
does not have to be disassembled to gain
access to the switches.
To prevent unauthorized personnel from
changing the configuration settings, a
security plate is attached to the bottom
of the Model 211’s enclosure. For con-
venience, the security plate provides a
summary of the configurable parameters
and related information. Refer to Appendix
A for a representative view. The security
plate is held in place by means of four
rubber bumpers (“feet”) that have built-in
screws. Using your fingers, remove the four
bumpers so that the plate can be removed.
Refer to Figure 2 for a detailed view of the
configuration switch assemblies.

Issue 1, December 2015 Model 211 User Guide
Page 14 Studio Technologies, Inc.
as long as associated monitor loudspeakers
are temporarily attenuated or muted.
Selecting the correct amount of gain for an
application might take a little experimenta-
tion. The goal is to bring the mic’s signal
up to line level, nominally –2 dBu for the
Model 211’s main output. Operating at this
signal level will help to ensure the delivery
of “clean” audio to the connected device.
It’s also acceptable to connect a line-level
audio source to the microphone input. In
this case selecting 0 dB (no gain) would
be appropriate.
The output of the Model 211’s microphone
preamplifier is used by the main output and,
by way of the compressor circuit, the talk-
back output. So creating a nice “hot” signal
will help to maintain the audio quality, spe-
cifically a high signal-to-noise ratio, when
driving lengthy cable runs.
Unfortunately, there’s no “perfect” gain set-
ting that this guide can recommend. The
two issues that impact the setting are
output sensitivity of the connected micro-
phone and the acoustical output level of
Figure 2. Bottom view of Model 211 showing
configuration switches and trim pots
Microphone Preamplifier Gain
and Phantom Power
Five switches are used to set the gain of
the microphone preamplifier. One switch
is used to select the on/off status of the
phantom power supply.
Microphone Preamplifier Gain
Switches SW1-1 through SW1-5 are used
to select the gain of the microphone pre-
amplifier. The choices are 20, 30, 40, 50,
and 60 dB; 0 dB (no gain) is also available.
Only one switch should be enabled at a
time. There’s no problem changing the gain
setting while the unit is operating. Audio
clicks or pops might occur during gain tran-
sitions, but this shouldn’t be a major issue
Figure 3. Microphone preamplifier gain switch
settings

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 15
the microphone’s user. With some headset
microphones, such as the Sennheiser HMD
26, selecting an initial setting of 40 dB is
appropriate. Users who speak loudly might
need to have the gain reduced to 30 dB.
Quiet users might need 50 dB of gain.
An LED indicator is provided as an aid
in correctly setting the gain of the micro-
phone preamplifier. Red in color, this LED
is located on the back panel adjacent to the
mic input connector and is labeled COMP.
Technically, this red LED lights whenever
the compressor circuitry is controlling the
dynamic range of the signal coming from
the microphone preamplifier. The threshold
is set to be 2 dB above the Model 211’s
nominal internal operating level. So a good
“rule of thumb” is to adjust the gain of the
microphone preamplifier such that the com-
pressor active LED lights (“flashes”) when
the connected microphone is sending signal
peaks. During normal operation the LED
should not remain fully lit when audio
is present on the mic input.
It’s important to remember that the compres-
sor active LED is used to assist in setting
the gain to the optimal value. It doesn’t
necessarily indicate that the main output’s
signal is being compressed. Unless specifi-
cally configured to perform otherwise, the
output of the compressor is only used for
the talkback output.
It’s expected that the 20 and 60 dB gain
settings will not often be used. But there are
always exceptions and that’s why they were
included. It’s possible that with a very “hot”
microphone, such as a phantom-powered
condenser, 20 dB of gain could be correct.
It’s also possible that a microphone with a
very low-level output, such as a ribbon-type,
would need 60 dB of gain. But in general,
the 30, 40, and 50 dB gain settings will
serve most applications.
Note that if no gain switch is set to its ac-
tive (on) position the preamplifier will oper-
ate at unity (0 dB) gain. This is provided for
compatibility when line-level signals need
to be connected to the microphone input.
However with a microphone connected as
the input source the 0 dB setting should
never be used. The issue is that with no
gain added to the microphone input signal,
the relative noise floor on the main and
talkback outputs will be much too high.
Phantom Power On/Off
The Model 211 can provide P48 phan-
tom power to the connected microphone.
Switch SW1-8 controls whether or not
phantom power is active. By phantom
power’s very nature it could be left applied
to the microphone input at all times. But
generally people prefer to turn it off unless
required for a specific microphone.
Figure 4. Phantom power switch settings
Headphone Source Selection
Switch assembly SW2 is used to configure
the source or sources that are routed to the
stereo headphone output. The headphone
sources are line input 1, line input 2, auxil-
iary input 1, and auxiliary input 2. The line
inputs are provided by way of the XLR con-
nectors located on the Model 211’s back
panel. The auxiliary inputs are available on
the Model 211’s main circuit board and are
only accessible if an optional IFB input card
has been installed or a special Model 211
configuration has been implemented.

Issue 1, December 2015 Model 211 User Guide
Page 16 Studio Technologies, Inc.
Each of the available input sources can be
assigned to the headphone output’s left
channel, right channel, or both the left and
right channels. The Model 211’s circuitry al-
lows any combination of input assignments
to be made.
Note that in some cases a user may wish
to wear a headset or a pair of headphones
in a left/right orientation opposite of what is
usual. In this situation the transducer desig-
nated for the left ear would actually supply
audio to the user’s right ear, and vice versa.
A specific application when this occurs is
where on-air talent needs to have a head-
set’s boom microphone come across the
right side of their face, rather than the more-
typical left side. In this case it’s important to
select the left- and right-channel headphone
source assignment accordingly. With the
Model 211’s flexible source selection there’s
no reason why users, such as on-air talent,
shouldn’t have their cue sources assigned
correctly.
There may be cases where a monaural
“single-muff” headset or headphone will
be connected to the Model 211’s head-
phone output. In this case the desired
source(s) should be routed only to the left
channel. No sources should be assigned
to the right channel. This will eliminate the
short-circuit current that could occur when
a 2-conductor (monaural) plug is mated
with the Model 211’s 3-conductor (stereo)
headphone output jack.
Headphone Output Mode
Switch SW1-6 allows a monaural head-
phone output to be created. This is accom-
plished by summing (adding) the selected
left- and right-channel cue signals. The
combined signals are sent to both the left-
and right-channel headphone output driver
circuits. The outputs of these circuits con-
nect, by way of 100 ohm series protection
resistors, to the headphone output jack.
The headphone output monaural mode fea-
ture was specifically included so that a spe-
cial 2-channel headphone mix mode can be
created. By enabling the mono mode, the
two front-panel user level controls (“pots”)
can be used to create the desired “mix” of
signals being sent to the headphone output.
Many applications, especially in production
settings, can benefit from this capability.
The desired cue sources must be carefully
assigned to take advantage of the monau-
ral mode. The first cue source should be
assigned, using the appropriate configura-
tion switch, to the left channel. Its output
level will be adjusted by the left control. The
second cue source should be assigned to
the right channel. Its output level will be
adjusted by the right control.
Figure 5. Left and right channel headphone
source selection settings

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 17
There is one limitation related to the
headphone mono output mode. It’s the
fact that the output will be 2-channel mon-
aural. Whatever signal is present on the
headphone output’s left channel will also
be present on the right channel. A stereo
headphone mix can’t be created. But in
most cases this limitation won’t overshad-
ow the benefit of being able to create the
mix. For signal-flow clarification please
review the block diagram located at the
end of this user guide.
Operating Modes
The eight switches associated with switch
assembly SW3 are used to configure the
Model 211’s operating modes. Technically,
these switches “talk” to the microcontroller
integrated circuit and associated software
that give the Model 211 its “smarts.” The
software has been carefully designed
to provide a number of different ways in
which the unit can function. It’s critical to
carefully review the available options and
choose the ones that best meet the needs
of a specific application. Note that switches
can be changed even while the Model 211
is powered up and operating. The unit’s op-
erating characteristics will change in “real-
time” in response to configuration changes.
Main Output Button Mode
Switches SW3-1 and SW3-2 configure
how the main output button functions.
Figure 6. Headphone output mode settings
Figure 7. Main output button mode settings
There are four available modes:
• Push to mute: In this mode the main out-
put is normally active. The main output
will mute whenever the button is pressed
and held. This is the “cough” mode typi-
cally used for on-air sports broadcasting
applications.
• Push to talk: In this mode the main out-
put is normally muted. The main output
will become active whenever the button
is pressed and held.
• Alternate action: In this mode the main
output will change between its active
and muted state whenever the button is
pressed. Upon power up the main output
will be in its muted state.
• Hybrid: This mode is a combination of
push to talk and alternate action. It’s
similar to the way talk buttons function
on user stations associated with broad-
cast and production intercom systems. If
the button is pressed and held, the main
output will become active until the button
is released. If the button is momentarily
“tapped” the main output will change
state. Upon power up the main output
will be in its muted state.

Issue 1, December 2015 Model 211 User Guide
Page 18 Studio Technologies, Inc.
Talkback Output Button Mode
Switch SW3-3 configures the way the talk-
back output button functions.
operation. In the level/level mode the two
controls operate independently, each con-
trolling the level of one of the headphone
output channels. This mode is generally
used for on-air broadcast applications
where independent cue signals are pro-
vided to the left- and right-headphone
channels. In the level/balance mode the
left rotary control sets the overall output
level for both headphone channels. The
right rotary control is used to adjust the
balance (the relative levels) of the left and
right channels. This mode is generally best
suited for applications where a stereo cue
source is being provided.
Reverse Left/Right Mode
Switch SW3-5 is used to select whether
the rotary controls are in the normal or
reverse left/right mode of operation. When
set to the normal mode, and level/level
mode is also selected, the left control
adjusts the level of headphone output’s left
channel. (This is the signal that appears
on the tip lead of the ¼-inch 3-conductor
jack.) The right control adjusts the level
of the right channel. When selected to
the normal mode, and the level/balance
mode is also selected, turning the balance
control in the counterclockwise direction
increases the perceived level of the left
channel, and vice versa.
As you may have already guessed, when
selecting the reverse left/right mode of op-
eration everything is reversed! To be more
specific, when selected for reverse mode,
Figure 8. Talkback output button mode settings
Two modes are available:
• Push to talk: In this mode the talkback
output is normally muted. The talkback
output will become active whenever the
button is pressed and held.
• Hybrid: This mode is a combination of
push to talk and alternate action. If the
button is pressed and held, the talkback
output will become active until the button
is released. If the button is momentarily
“tapped” the talkback output will change
state. Upon power up the talkback output
will be in its muted state.
Headphone Output Operating
Modes
The user is provided with two rotary level
controls (“pots”) that are associated with
the stereo headphone output. Switches
SW3-4, SW3-5, and SW3-6 are used to
configure the way the controls function.
With just these three switches a wide
range of operating modes can be config-
ured. Carefully reviewing the capabilities
of the available functions may prove
worthwhile.
Dual-Channel or Stereo Mode
Switch SW3-4 is used to select whether
the controls provide a dual-channel (“level/
level”) or stereo (“level/balance”) mode of
Figure 9. Headphone control mode settings

Model 211 User Guide Issue 1, December 2015
Studio Technologies, Inc. Page 19
and the level/level mode is also selected,
the left control adjusts the headphone out-
put’s right channel (output jack’s ring lead)
while the right control adjusts the left chan-
nel. When set to the reverse mode, and the
level/balance is also selected, turning the
balance control in the counterclockwise
direction increases the perceived level of
the right channel, and vice versa.
The reverse mode is provided specifically
for cases where a headset’s left and right
earpieces are placed on a user’s head
in a reverse orientation. This ensures that
the user is provided with a consistent
and easy-to-use set of headphone level
controls.
Minimum Level Mode
Switch SW3-6 is used to configure the
headphone output’s minimum level. In the
–40 dB mode the minimum headphone
output level is 40 dB below maximum. The
headphone output channels will never fully
mute. This ensures that any audio signal
present on the selected Model 211 inputs
will always be present on the headphone
output. In most on-air broadcast applica-
tions this is the appropriate setting.
When the full mute mode is selected,
and the level/level mode is also selected,
moving either control to its fully counter-
clockwise position will cause its associated
channel to fully mute.
When the full mute mode is selected,
and the level/balance mode is also se-
lected, turning the level control to its fully
counterclockwise position will cause both
headphone channels to mute. Turning the
balance control to either its fully clock-
wise or fully counterclockwise position will
cause the appropriate channel to mute.
Selecting the full mute mode may be ap-
propriate for applications where minimizing
the chance of audio “leakage” is impor-
tant. This could occur when the connected
headset or headphones are at times
placed on a desk or tabletop.
Main Output Source
Switch SW3-7 is used to select which
audio source is routed to the main output.
The choices are the output of the micro-
phone preamplifier or the output of the
compressor circuit. For most on-air ap-
plications the output of the microphone
preamplifier is the desired source. This will
provide the most natural audio quality with
the potential for a large amount of dynamic
range.
In some applications it may be desirable
for the output of the compressor circuit to
be routed to the main output. Appropriate
applications could include on-air broadcast
situations where non-professional talent
is present. Controlling the dynamic range
of the audio signals on the main output
can limit the chance of cable crosstalk and
Figure 10. Headphone control operation
settings Figure 11. Headphone output minimum level
settings

Issue 1, December 2015 Model 211 User Guide
Page 20 Studio Technologies, Inc.
equipment overload. Another typical applica-
tion where using the output of the compres-
sor would be when the Model 211’s system
mode is selected for production. In this case
the main output would be used as an ad-
ditional talkback output and dynamic range
control could be beneficial.
System Mode
Switch SW3-8 is used to configure the
overall operating mode of the Model 211.
Specifically, it determines how the main
output operates vis-à-vis the talkback out-
put. Understanding how the two modes
impact overall system operation will ensure
that correct operation and maximum usabil-
ity will occur. When selected to the on-air
mode, the main output will mute whenever
the talkback output is active. The on-air
mode should be selected for all on-air
broadcast applications. It’s imperative that
the main output be muted whenever on-air
talent uses the talkback output to communi-
cate with production personnel.
used, for example, as an additional talkback
output. In this way the main and talkback
outputs can be used independently, with
neither impacting the other. This also allows
both buttons to be used simultaneously.
When selected for the correct application,
the production mode can prove to be very
useful. But it’s not appropriate for on-air use!
Adjusting the Line Input
Trim Pots
As has been previously mentioned, associ-
ated with the two line inputs are trim pots
that allow the input levels to be adjusted.
The two trim pots are accessible by way
of round openings in the bottom of the
Model 211’s enclosure. By adjusting these
trim pots, signals with a nominal level of
–12 dBV to +6 dBu can be effectively used
as cue sources. Unfortunately, there are
no definitive rules regarding how best to
adjust the trim pots, but some suggestions
may prove to be valuable. Depending on
how the line inputs are utilized, the trim pots
can be used to either adjust the absolute
level of each line input signal or to adjust
the relative level of the signals when com-
pared to other sources. The following exam-
ples may provide some clarification.
Let’s begin with an application that has a
stereo cue source connected to the line in-
puts. The cue source selection switches are
configured to create a stereo headphone
output with line input 1 assigned to the left
channel and line input 2 assigned to the
right channel. Begin the trim pot adjustment
process by moving the user level controls
(located on the front panel) to their detent
(50% of rotation) positions. Then, with the
stereo cue source providing signal at its
normal level, adjust the trim pots to provide
a comfortable level to the connected head-
phones. The user can now, in response to
Figure 12. Main output source settings
Figure 13. System mode settings
When the system mode is set for produc-
tion, the main output is never muted in re-
sponse to the talkback output being active.
This mode allows the main output to be