Studio Technologies 374A Datasheet

Model 374A Intercom Beltpack

Four Channels, Dante® Technology

Key Features

• Dante audio-over-Ethernet technology

• Four independent talk and listen channels

• Supports dynamic and electret microphones

• 5-pin female XLR headset connector

• Configurable operating modes

• Excellent audio quality

• Uses STcontroller for configuration

• AES67 and Dante Domain Manager™ support

• Power-over-Ethernet (PoE) powered

Introduction

The Model 374A Intercom Beltpack begins with the

features offered by traditional party-line intercom user

devices and adds a range of new capabilities along with

the advanced performance and flexibility 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 permanently 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 5422 Dante Intercom Audio

Engine. 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 using the STcontroller software application.

Configurable parameters include electret microphone

powering, microphone preamplifier gain, talk button opera

tion, and headphone channel assignment. User features

include integrated sidetone, remote mic kill (“talk off”),

and monitor-only modes. The wide range of capabilities,

along with the excellent audio quality provided by the

digital 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 connection 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.

The STcontroller software application is used to select

the unit’s operating parameters. Four talk pushbutton

switches can be configured for optimal operation. Four

push-in/push-out (“pop out”) rotary controls make it easy

to set and maintain the desired headphone output level.

The Model 374A’s enclosure is made from an aluminum

alloy which offers both light weight 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 chan

nels is excellent, with low distortion, low noise, and high

headroom. Careful circuit design and rugged components

ensure long, reliable operation. A wide range of applica

tions can be supported, including sports and entertainment

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50657-0618, Issue 1

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

technology. 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 com

patible and compliant with the Dante Domain Manager™

software application.

Two bi-color LEDs provide an indication of the Dante con

nection 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 coun-

ter to the less-than-stellar reputation of typical party-line

(PL) intercom audio. A low-noise, wide dynamic-range

microphone preamplifier and associated voltage-con

trolled-amplifier (VCA) dynamics controller (compressor)

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 domain,

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 sampling 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-performance 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.

Configuration Flexibility

A highlight of the Model 374A is its ability to be easily

configured to meet the needs of specific users and ap

plications. All configuration choices are made using the

STcontroller software application that communicates with

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the Model 374A by way of an Ethernet network connection.

Configurable parameters include microphone power and

preamplifier gain, sidetone audio operationl, talk button

­operation, and headphone monitoring.

The microphone input can be selected for compatibility with

dynamic or electret (DC-powered) microphones. The gain

of the microphone preamplifier can be selected from among

four choices, two for supporting dynamic microphones and

two for supporting electret microphones. These choices

allow compatibility with a variety of microphones that are

part of broadcast and intercom headsets.

A unique Model 374A feature is the ability to individu

ally configure the way in which the four talk pushbutton

­switches function; four choices are available. For standard

intercom beltpack operation either

Talk/Tap to Latch

operation can be selected. For situations

Push to Talk

where only monitoring of an intercom channel is desired a

Talk Disabled

ing-only situations the

mode is available. And for advanced monitor-

Talk Disabled/Phones Tap to Latch

mode can be selected such that a button will serve in an

audio on/off role.

Four audio channels arrive via Dante and are destined

for the 2-channel headphone output. Each input source

can be independently 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 environments to be created, including stereo,

single-channel monaural, and dual-channel monaural.

or

Push to

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Studio Technologies, Inc. Model 374A Intercom Beltpack, Issue 1, Page 2

Ethernet Data and PoE

The Model 374A connects to an Ethernet data network

using a standard 100 Mb/s twisted-pair Ethernet inter

face. The physical 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.

The Model 374A’s operating power is provided by way

of the Ethernet interface using the 802.3af Power-over-

Ethernet (PoE) standard. This allows fast and efficient

interconnection 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.

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Future Capabilities and Firmware
Updating

The Model 374A was designed such that its capabilities and

performance can be enhanced in the future. A USB connec

tor, 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.

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Model 374A Specifications

Power Source:

Power-over-Ethernet (PoE): class 1 (very low power, ≤3.84 watts)
per IEEE® 802.3af

Network Audio Technology:

Type: Dante audio-over-Ethernet
AES67-2013 Support: yes
Dante Domain Manager (DDM) Support: yes
Bit Depth: up to 24
Sample Rate: 48 kHz
Number of Transmitter (Output) Channels: 4
Number of Receiver (Input) Channels: 4
Dante Audio Flows: 4; 2 transmitter, 2 receiver

Network Interface:

Type: 100BASE-TX, twisted-pair Ethernet, Power-over-Ethernet (PoE)
supported
Data Rate: 100 Mb/s (10 Mb/s and 1000 Mb/s “GigE” Ethernet not
supported)

Audio Channels: 4 talk, 4 listen

Microphone Input:

Compatibility: dynamic or electret (low-voltage DC-powered) micro
phones
Type: unbalanced
Electret Microphone Power: 5 volts DC via 2.21 k resistor, selectable
on/off
Gain, configured for dynamic microphones: 42 or 48 dB, selectable,
ref. –60 dBu input to Dante output (–20 dBFS nominal)
Gain, configured for electret microphones: 22 or 30 dB, selectable,
ref. –60 dBu input to Dante output (–20 dBFS nominal)
Frequency Response: 50 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.02%
Dynamic Range: 75 dB

Compressor:

Threshold: 1 dB above nominal level (–19 dBFS)
Slope: 2:1
Status LED: compressor active

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Headphone Output:

Type: 2-channel
Compatibility: intended for connection to stereo (dual-channel)
or monaural (single-channel) headsets with nominal impedance of
50 ohms or greater
Maximum Output Voltage: 3.8 Vrms, 1 kHz, 150 ohm load
Frequency Response: 20 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.002%
Dynamic Range: >100 dB

Connectors:

Headset: 5-pin female XLR
Ethernet: Neutrik NE8FBH etherCON RJ45 receptacle
USB: type A receptacle (located inside Model 374A’s enclosure and
used only for application firmware updates)

Configuration: requires Studio Technologies STcontroller software
application, version 1.06.00 and later (STcontroller is compatible with
Windows version 7 and later)

Environmental:

Operating Temperature: 0 to 50 degrees C (32 to 122 degrees F)
Storage Temperature: –40 to 70 degrees C (–40 to 158 degrees F)
Humidity: 0 to 95%, non-condensing
Altitude: not characterized

Dimensions (Overall):

3.6 inches wide (9.2 cm)

1.6 inches high (4.0 cm)

4.8 inches deep (12.6 cm)

Mounting: intended for portable applications; contains integral belt
clip; optional MBK-01 Mounting Bracket Kit allows Model 374A to be
permanently mounted

Weight:

Specifications subject to change without notice.

0.6 pounds (0.3 kg)

Studio Technologies, Inc.

Skokie, Illinois USA
© by Studio Technolog

ies, Inc., June 2018

studio-tech.com

Studio Technologies, Inc. Model 374A Intercom Beltpack, Issue 1, Page 3