Studio Technologies 374A Manuale utente
Copyright © 2021 by Studio Technologies, Inc., all rights reserved
studio-tech.com
50658-0321, Issue 5
User Guide
Issue 5, March 2021
This User Guide is applicable for serial numbers
M374A-04001 and later with application firmware 2.1 and later
Model 374A Intercom Beltpack
This page intentionally left blank.
Model 374A User Guide Issue 5, March 2021
Studio Technologies, Inc. Page 3
MODEL 374A
INTERCOM BELTPACK
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 8
Operation ...................................................................... 14
Technical Notes ............................................................. 20
Specifications ................................................................ 24
Appendix A .................................................................... 25
Issue 5, March 2021 Model 374A User Guide
Page 4 Studio Technologies, Inc.
MODEL 374A
INTERCOM BELTPACK
Revision History
Issue 5, March 2021:
1. Documents addition of remote control inputs.
Issue 4, February 2021:
1. Documents expansion of Call Indication function.
Issue 3, August 2019:
1. Documents revision to STcontroller (version 2.02.00 and later) which separates
microphone power and microphone gain configuration.
Issue 2, April 2019:
1. Documents new receive and send call function.
Issue 1, June 2018:
1. Initial release.
Model 374A User Guide Issue 5, March 2021
Studio Technologies, Inc. Page 5
MODEL 374A
INTERCOM BELTPACK
Introduction
The Model 374A Intercom Beltpack
begins with the features offered by tradi-
tional party-line intercom user devices and
adds a range of new capabilities along
with the advanced performance and flex-
ibility that Dante® audio-over-Ethernet
provides. With four independent talk and
listen channels the Model 374A bridges
the gap between typical single- and dual-
channel party-line devices and permanent-
ly installed multi-channel intercom panels.
Imagine the possibilities—four channels
of high-quality party-line intercom in a
compact, user-worn package.
Over a standard IP network, multiple
Model 374A units can be used in party-line
(PL) intercom applications with help from
an external Dante-enabled audio matrix
such as the Studio Technologies’ Model
5421 or Model 5422A Dante Intercom
Audio Engine units. Or, units can be used
“point-to-point” or interfaced with Dante-
compatible matrix intercom systems.
Only a single Power-over-Ethernet (PoE)
connection is required for operation. Key
user features can be easily configured us-
ing the STcontroller software application.
Configurable parameters include electret
microphone powering, microphone pre-
amplifier gain, talk button operation, call
receive indication, remote control inputs,
and headphone channel assignment. User
features include integrated sidetone, re-
mote mic kill (“talk off”), call receive and
send, and audio monitor-only modes. The
wide range of capabilities, along with the
excellent audio quality provided by the digi-
tal audio signal path, offers a unique and
powerful user experience.
Set up and configuration of the Model 374A
is simple. An etherCON® RJ45 receptacle
is used to interconnect with a standard
twisted-pair Ethernet port associated with
a local-area network (LAN). This connec-
tion provides both power and bidirectional
digital audio. A broadcast or intercom-style
stereo or monaural headset with a dynamic
or electret (DC-powered) microphone
interfaces with the unit using a 5-pin XLR
connector. A 3-conductor 3.5 mm jack al-
lows connection of two external switches
or contact closures to activate two selected
talk channels.
The STcontroller software application is
used to select the unit’s operating param-
eters. Four talk pushbutton switches can
be configured for optimal operation. Four
push-in/push-out (“pop out”) rotary con-
trols make it easy to set and maintain the
desired headphone output level. The Model
374A’s enclosure is made from an alumi-
num alloy which offers both light weight
Figure 1. Model 374A Intercom Beltpack top and bottom views
Issue 5, March 2021 Model 374A User Guide
Page 6 Studio Technologies, Inc.
MODEL 374A
INTERCOM BELTPACK
and ruggedness. A stainless steel “belt
clip,” located on the back of the unit,
allows direct attachment to a user’s
clothing.
The audio quality of the Model 374A’s
four audio channels is excellent, with low
distortion, low noise, and high headroom.
Careful circuit design and rugged com-
ponents ensure long, reliable operation.
A wide range of applications can be sup-
ported, including sports and entertain-
ment TV and radio events, streaming
broadcasts, corporate and government AV
installations, and post-production facilities.
Dante Audio-over-Ethernet
Audio data is sent to and received from
the Model 374A using the Dante audio-
over-Ethernet media networking technol-
ogy. As a Dante-compliant device, the
Model 374A’s four audio output (Dante
transmitter) and four audio input (Dante
receiver) channels can be interconnected
(routed) with other devices using the
Dante Controller software application. The
Dante transmitter and receiver channels
are limited to supporting four Dante flows,
two in each direction. The digital audio’s
bit depth is up to 24 with a sampling rate
of 48 kHz. The Model 374A is AES67
compatible and compliant with the Dante
Domain Manager™ software application.
Two bi-color LEDs provide an indication
of the Dante connection status. The Dante
Controller’s Identify command takes on a
unique role with the Model 374A. Not only
will it cause the talk button LEDs to light
in a unique highly visible sequence, it can
also be configured to turn off any active
talk channels.
Audio Quality
The Model 374A’s completely “pro”
performance is counter to the less-than-
stellar reputation of typical party-line
(PL) intercom audio. A low-noise, wide
dynamic-range microphone preamplifier
and associated voltage-controlled-am-
plifier (VCA) dynamics controller (com-
pressor) ensures that microphone audio
quality is preserved while minimizing the
chance of signal overload. DC power
to support electret microphones can be
enabled if necessary. The output of the
microphone preamp and compressor is
routed to an analog-to-digital converter
(ADC) section that supports a sampling
rate of 48 kHz with a bit depth of up to 24.
The audio signal, now in the digital do-
main, travels through the processor and
on to the Dante interface section where it
is packetized and prepared for transport
over Ethernet.
Audio input signals arrive via four Dante
receiver channels. The supported sam-
pling rate is 48 kHz with a bit depth of
up to 24. The audio signals pass into the
Model 374A’s processor where channel
routing, headphone level control, and
sidetone creation are performed within
the digital domain. This provides flexibility,
allowing for precise control of the audio
signals and eliminates the need for the
four rotary level controls from having to
directly handle analog audio signals. The
audio signals destined for the 2-channel
headphone output are sent to a high-per-
formance digital-to-analog converter and
then on to robust driver circuitry. High
signal levels can be provided to a variety
of headsets, headphones, and earpieces.
Model 374A User Guide Issue 5, March 2021
Studio Technologies, Inc. Page 7
MODEL 374A
INTERCOM BELTPACK
Call Function
A call function allows Model 374A users to
receive and send channel-specific visual
alert signals. Using 20 kHz tones, the call
signals are sent within the audio chan-
nels (“in band”) allowing interoperability
between multiple Model 374A units as well
as being compatible with legacy party-line
intercom systems. Call signals can be use-
ful to indicate to users that they are needed
“on headset” or should be actively listening
to an intercom channel. The call function
can also be used to provide realtime cues
to production personnel during the running
of live events. Call signals present on the
four audio input (Dante receiver) channels
can be detected and displayed. To opti-
mize for specific applications, a configura-
tion choice allows the way in which the
Model 374A will display Call when 20 kHz
has been detected. Pushbutton 4, on the
Model 374A’s top panel, can be configured
to serve as a call button. This allows a call
signal to be generated for talk channels 1,
2, and 3.
Configuration Flexibility
A highlight of the Model 374A is its abil-
ity to be easily configured to meet the
needs of specific users and applications.
All configuration choices are made using
the STcontroller software application that
communicates with the Model 374A by way
of an Ethernet network connection. Con-
figurable parameters include microphone
power and preamplifier gain, sidetone
audio operation, talk button operation, call
indication, remote control inputs, and head-
phone monitoring.
The microphone input can be selected for
compatibility with dynamic or electret (DC-
powered) microphones. The gain of the mi-
crophone preamplifier can be selected from
among four choices. These allow compat-
ibility with a variety of microphones that are
part of broadcast and intercom headsets.
A unique Model 374A feature is the ability
to individually configure the way in which
the four talk pushbutton switches function;
four choices are available. For standard
intercom beltpack operation either Push
to Talk or Push to Talk/Tap to Latch opera-
tion can be selected. For situations where
only monitoring of an intercom channel is
desired a Talk Disabled mode is available.
And for advanced monitoring-only situa-
tions the Talk Disabled/Phones Tap to Latch
mode can be selected such that a button
will serve in an audio on/off role.
Configuration choices allow the two remote
control inputs to be individually assigned
to activate any one of the four talk channel
functions.
Four audio channels arrive via Dante and
are destined for the 2-channel headphone
output. Each input source can be indepen-
dently routed to the left headphone chan-
nel, right headphone channel, or both the
left and right headphone channels. This
flexibility allows a variety of listening envi-
ronments to be created, including stereo,
single-channel monaural, and dual-channel
monaural.
Ethernet Data and PoE
The Model 374A connects to an Ethernet
data network using a standard 100 Mb/s
twisted-pair Ethernet interface. The physi-
cal interconnection is made by way of a
Neutrik® etherCON RJ45 receptacle. While
compatible with standard RJ45 plugs,
etherCON allows a ruggedized and locking
interconnection for harsh or high-reliability
environments. An LED displays the status
of the network connection.
Issue 5, March 2021 Model 374A User Guide
Page 8 Studio Technologies, Inc.
MODEL 374A
INTERCOM BELTPACK
The Model 374A’s operating power is pro-
vided by way of the Ethernet interface using
the 802.3af Power-over-Ethernet (PoE) stan-
dard. This allows fast and efficient intercon-
nection with the associated data network.
To support PoE power management, the
Model 374A’s PoE interface reports to the
power sourcing equipment (PSE) that it’s
a class 1 (very low power) device.
Future Capabilities and
Firmware Updating
The Model 374A was designed such that
its capabilities and performance can be
enhanced in the future. A USB connector,
located on the unit’s main circuit board
(underneath the unit’s cover), allows the
application firmware (embedded software)
to be updated using a USB flash drive.
The Model 374A uses Audinate’s Ultimo™
integrated circuit to implement the Dante
interface. The firmware in this integrated
circuit can be updated via the Ethernet
connection, helping to ensure that its
capabilities remain up to date.
Getting Started
What’s Included
Included in the shipping carton are a Model
374A Intercom Beltpack and instructions
on how to obtain an electronic copy of this
guide. As a device that is Power-over-
Ethernet (PoE) powered, no external
power source is provided. In most applica-
tions an Ethernet switch with the required
PoE capability will be utilized.
Connections
In this section signal interconnections will
be made using the two connectors located
on the bottom of the Model 374A’s enclo-
sure. An Ethernet data connection with
Power-over-Ethernet (PoE) capability will
be made using either a standard RJ45
patch cable or an etherCON protected
RJ45 plug. A dual-channel or single-
channel (dual- or single-ear) headset
will be connected using a cable-mounted
5-pin male XLR connector. Some applica-
tions will use the 3-conductor 3.5 mm jack
that provides access to the Model 374A’s
two remote control inputs.
Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that
supports Power-over-Ethernet (PoE) is
required for Model 374A operation. This
one connection will provide both the Ether-
net data interface and power for the Model
374A’s circuitry. A 10BASE-T connection
is not sufficient and a 1000BASE-T (GigE)
connection is not supported unless it can
automatically “fall back” to 100BASE-TX
operation. The Model 374A supports
Ethernet switch power management,
enumerating itself as a PoE class 1
device. Any source that is compliant with
the IEEE® 802.3af standard will function
correctly. Should the selected Ethernet
switch port support Energy-Efficient
Ethernet (EEE) it must be disabled to
help ensure reliable Dante operation.
The Ethernet connection is made by way
of a Neutrik etherCON protected RJ45
receptacle that is located on the bottom
of the Model 374A’s enclosure. This allows
connection by way of a cable-mounted
etherCON connector or a standard RJ45
plug. The Model 374A’s Ethernet interface
supports auto MDI/MDI-X so that a cross-
over cable will never be required.
Model 374A User Guide Issue 5, March 2021
Studio Technologies, Inc. Page 9
MODEL 374A
INTERCOM BELTPACK
Headset Connection
The Model 374A provides a 5-pin female
XLR connector that interfaces with the
microphone and headphone connections
of an intercom or broadcast-style headset.
Refer to Figure 2 for connection details.
The microphone input connections are
compatible with most unbalanced dynamic
or electret (low-voltage DC-powered)
microphones. A balanced dynamic micro-
phone should, in most cases, also function
correctly if the signal – (low) is connected
to Model 374A’s mic in –/shield connec-
tion. No support is provided for micro-
phones that require P12 or P48 phantom
power.
To allow users of stereo (dual-earpiece or
“double muff”) headsets to hear a monau-
ral version of the two headphone output
channels does not require special wiring of
the 5-pin male XLR mating connector. The
headset’s left headphone channel should
always be wired to pin 4 and the right
headphone channel to pin 5. Configuration
choices, discussed later in this guide, can
then be used to create the desired mon-
aural output. It’s important not to connect
together (short) pins 4 and 5 of the Model
374A’s headset connector as damage to
the Model 374A’s output circuitry could
result.
Monaural (single-earpiece or “single muff”)
headsets should be wired such that its
headphone is wired only to pin 4; pin 5
should be remain unused. Configuration
choices, discussed later in this guide, can
be used to create a monaural output.
It’s possible that some Beyerdynamic
headset interconnecting cable assemblies
terminate the earpiece’s left and right con-
nections opposite from what the Model
374A and other broadcast equipment
require. These cables may terminate the
left earpiece to pin 5 of the XLR connec-
tor and the right earpiece to pin 4. If this
condition is present it will require reversing
or “flipping” the two wires in a headset’s
5-pin male XLR connector such that the left
earpiece connects to pin 4 and the right
earpiece to pin 5.
Remote Control Inputs
Provision has been made to allow exter-
nal switches or contact closures to mimic
the operation of one or two of the four talk
pushbutton switches. The exact functioning
of the two remote control inputs is deter-
mined by configuration settings, details of
which are discussed later in this guide. A
3-conductor 3.5 mm jack is located on the
Model 374A’s bottom panel and provides
access to the two remote control inputs.
The input circuitry is “active low,” which
means that they are enabled whenever
they are connected (shorted) to the com-
mon connection. Technically, each remote
control input is created with a 3.4 k ohm re-
sistor connected to +3.3 volts DC that acts
as an input “pull up.” Additional resistors
and capacitors provide ESD protection,
minimizing the chance of damage to an
input due to static discharge or other extra-
neous signals. A current flow of less than
one milliampere is required for a remote
control input to be recognized as active.
Figure 2. Headset connection pinout chart
Issue 5, March 2021 Model 374A User Guide
Page 10 Studio Technologies, Inc.
MODEL 374A
INTERCOM BELTPACK
Prepare an interconnecting cable and
associated 3-conductor 3.5 mm plug to
reflect that the tip lead is used by Remote
Control Input 1, the ring lead by Remote
Control Input 2, and the sleeve lead is the
connection to common. Refer to Figure 3
for connection details.
circuit is limited to two. These can either be
unicast, multicast, or a combination of the
two. If the Model 374A’s transmitter chan-
nels need to be routed using more than
two flows it’s possible that an intermediary
device, such as the Studio Technologies’
Model 5422 Dante Intercom Audio Engine,
can be used to “repeat” the signals.
The four Dante receiver (Rx) channels
associated with the Model 374A’s audio in-
puts also need to be routed to the desired
Dante transmitter (Tx) channels. These four
audio signals can be sent to the Model
374A’s 2-channel headphone output.
The Model 374A supports an audio sample
rate of 48 kHz with no pull-up/pull-down
values available. The Model 374A can serve
as the Leader clock for a Dante network but
in most cases it will be configured to “sync”
to another device.
The Model 374A has a default Dante
device name of ST-M374A- followed by a
unique suffix. The suffix identifies the spe-
cific Model 374A that is being configured.
The suffix’s actual alpha and/or numeric
characters relate to the MAC address of
the unit’s Ultimo integrated circuit. The four
Dante transmitter (Tx) channels have de-
fault names of Ch1, Ch2, Ch3, and Ch4.
The four Dante receiver (Rx) channels have
default names of Ch1, Ch2, Ch3, and Ch4.
Using Dante Controller the default device
name and channel names can be revised
as appropriate for the specific application.
Model 374A Configuration
Many of the Model 374A’s operating
parameters can be configured to match
the needs of specific applications. The
STcontroller software application is used to
observe a unit’s current configuration and
perform any changes that are required. No
Figure 3. 3-conductor 3.5 mm (TRS) remote
control in pinout diagram
Dante Configuration
For audio to pass to and from the Model
374A requires that several Dante-related
parameters be configured. These configu-
ration settings will be stored in non-volatile
memory within the Model 374A’s circuitry.
Configuration will typically be done with
the Dante Controller software application
which is available for download free of
charge at audinate.com. Versions of Dante
Controller are available to support Win-
dows® and OS X® operating systems.
The Model 374A uses the Ultimo 4-input/
4-output integrated circuit to implement
the Dante architecture.
The four Dante transmitter (Tx) channels
associated with the Model 374A’s Dante
interface must be assigned to the desired
receiver (Rx) channels. This achieves rout-
ing the Model 374A’s four talk output audio
channels to the device (or devices) that will
be “listening” to them. Within Dante Con-
troller a “subscription” is the term used for
routing a transmitter flow (a group of out-
put channels) to a receiver flow (a group of
input channels). The number of transmitter
flows associated with an Ultimo integrated
Altri manuali per 374A
2
Questo manuale è adatto per i seguenti modelli
1
Indice
Altri manuali Studio Technologies Sistema di interfono
Studio Technologies
Studio Technologies 45DC Manuale utente
Studio Technologies
Studio Technologies 348 Manuale utente
Studio Technologies
Studio Technologies 374A Manuale utente
Studio Technologies
Studio Technologies 348 Manuale utente
Studio Technologies
Studio Technologies 373A Manuale utente
Studio Technologies
Studio Technologies 348 Manuale utente
Studio Technologies
Studio Technologies 371 Manuale utente
Studio Technologies
Studio Technologies 370A Manuale utente
Studio Technologies
Studio Technologies M45 Interface Manuale utente
Studio Technologies
Studio Technologies 370 Manuale utente
Studio Technologies
Studio Technologies 342 Manuale utente
Studio Technologies
Studio Technologies 354 Manuale utente
Studio Technologies
Studio Technologies Dante 5422A Manuale utente
Studio Technologies
Studio Technologies 45A Manuale utente
Studio Technologies
Studio Technologies 380 Manuale utente
Studio Technologies
Studio Technologies 372A Manuale utente
Studio Technologies
Studio Technologies 5421 Manuale utente
Studio Technologies
Studio Technologies 5304 Manuale utente
Studio Technologies
Studio Technologies 374A Manuale utente
Studio Technologies
Studio Technologies 348 Manuale utente
