Studio Technologies 374 Manuel utilisateur
Copyright © 2016 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50627-0916, Issue 2
User Guide
Issue 2, September 2016
This User Guide is applicable for serial numbers
M374-00151 and later with application firmware 1.3 and later
and Dante firmware 2.0 (Ultimo 3.10.1.12) and later
Model 374 Intercom Beltpack
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Model 374 User Guide Issue 2, September 2016
Studio Technologies, Inc. Page 3
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 7
Operation ...................................................................... 15
Technical Notes ............................................................. 18
Specifications ................................................................ 21
Issue 2, September 2016 Model 374 User Guide
Page 4 Studio Technologies, Inc.
Revision History
Issue 2, September 2016:
1. Revised to show support for 44.1 and 48 kHz sampling rates.
Issue 1, August 2016:
1. Initial release.
Model 374 User Guide Issue 2, September 2016
Studio Technologies, Inc. Page 5
Introduction
The Model 374 Intercom Beltpack starts
with the features offered by traditional
broadcast party-line (PL) intercom user
devices and adds a range of new features
along with the advanced performance and
capabilities that Dante audio-over-Ethernet
provides. With four independent talk and
listen channels the Model 374 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 374 units can be used in PL inter-
com applications with help from an exter-
nal Dante-enabled audio matrix. Or, units
can be used “point-to-point” or directly
interfaced with ports on compatible matrix
intercom systems. Only a single Power-
over-Ethernet (PoE) connection is required
for operation. Key user features can be
easily configured including preamplifier
gain, independent talk button operation,
and individual-channel headphone signal
routing. User features include integrated
sidetone, remote talk channel turn off
(“mic kill”), and monitor only modes. This
capability, along with the great audio qual-
ity provided by the digital audio signal
path, offers a unique and powerful user
experience.
Set up and configuration of the Model
374 is simple. An etherCON® RJ45 jack
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 microphone interfaces with the
unit using a 5-pin XLR connector. DIP
switches and software-based configura-
tion are used to establish the unit’s operat-
ing parameters. Four “push-in/push-out”
rotary level controls make it easy to set
and maintain the desired headphone out-
put. The Model 374’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 374’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.
Figure 1. Model 374 Intercom Beltpack top and bottom views
Issue 2, September 2016 Model 374 User Guide
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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 374 using the Dante audio-over-
Ethernet media networking technology.
As a Dante-compliant device, the Model
374’s four output (Dante transmitter) and
four input (Dante receiver) audio channels
can be interconnected (routed) with other
devices using the Dante Controller soft-
ware 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 44.1 or 48 kHz.
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 374. Not only
will it cause the talk button LEDs to light
in a unique highly visible sequence, it will
also turn off any active talk channels.
Audio Quality
The Model 374’s completely “pro” perfor-
mance is counter to the less-than-stellar
reputation of typical intercom audio.
A low-noise, wide dynamic-range micro-
phone preamplifier and associated volt-
age-controller-amplifier (VCA) dynamics
controller (compressor) ensures that mic
input audio quality is preserved while
minimizing the chance of signal overload.
The output of the microphone preamp and
compressor is routed to an analog-to-digi-
tal converter (ADC) section that supports a
sampling rate of 44.1 and 48 kHz with a bit
depth of up to 24. The audio signal, now in
the digital domain, routes through the pro-
cessor and on to the Dante interface sec-
tion where it is packetized and prepared
for transport over Ethernet.
Audio input signals arrive via the four
Dante receiver channels and pass into
the Model 374’s processor. The sampling
rate will be 44.1 or 48 kHz with a bit depth
of up to 24. Channel routing, headphone
level control, and sidetone creation are
performed within the digital domain. This
provides flexibility, allows precise control,
and keeps the five level potentiometers
(channels 1-4 and sidetone) from having
to directly handle analog audio signals.
The audio signals destined for the 2-chan-
nel 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 374 is its ability
to be easily configured to the meet the
needs of specific users and applications.
Three DIP switches allow control of the
microphone preamplifier gain and a button
backlight mode. A software-based configu-
ration mode allows optimizing talk button
operation and the routing of the audio
inputs to the headphone output channels.
The gain of the microphone preamplifier
can be selected from among four choices.
This allows compatibility with the dynamic
microphones that are part of the many
industry-standard broadcast and intercom
headsets. A button backlight mode can
be enabled to ensure that an LED associ-
ated with each of the four talk buttons
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Studio Technologies, Inc. Page 7
will always be lit. This is provided for
applications where there is little or no ambi-
ent lighting available to assist in identifying
button locations.
A highly unique Model 374 feature is the
ability to individually configure the way in
which the four pushbutton switches func-
tion; four choices are available. For stan-
dard intercom beltpack operation either
push to talk or push to talk/tap to latch
operation can be selected. For situations
where only monitoring of an intercom
channel is desired a talk disable mode is
available. And for advanced monitoring-
only situations a 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 can be independently
routed to the left and right, left-only, or
right-only headphone channels. This flex-
ibility allows a variety of listening environ-
ments to be created, including stereo,
single-channel monaural, and dual-
channel monaural.
Ethernet Data and PoE
The Model 374 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 connector.
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 374’s operating power is pro-
vided by way of the Ethernet interface us-
ing the 802.3af Power-over-Ethernet (PoE)
standard. This allows fast and efficient
interconnection with the associated data
network. To support PoE power man-
agement, the Model 374’s PoE interface
reports to the power sourcing equipment
(PSE) that it’s a class 1 (very low power)
device. If a PoE-enabled Ethernet port
can’t be provided by the associated Ether-
net switch a low-cost PoE midspan power
injector can be utilized.
Future Capabilities and
Firmware Updating
The Model 374 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 374 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 374 Intercom Beltpack and a print-
ed copy of this guide. As a device that is
Power-over-Ethernet (PoE) powered, no
external power source is provided. Should
a PoE midspan power injector be required
it must be purchased separately.
Connections
In this section signal interconnections
will be made using the two connectors
located on the bottom of the Model 374’s
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enclosure. 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- or single-earpiece
headset (stereo or monaural) will be con-
nected using a cable-mounted 5-pin male
XLR connector.
Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that
supports Power-over-Ethernet (PoE) is
required for Model 374 operation. This one
connection will provide both the Ethernet
data interface and power for the Model
374’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 374 supports Ether-
net switch power management, enumerat-
ing itself as a PoE class 1 device.
The Ethernet connection is made by way
of a Neutrik etherCON protected RJ45
connector that is located on the bottom
of the Model 374’s enclosure. This allows
connection by way of a cable-mounted
etherCON connector or a standard RJ45
plug. The Model 374’s Ethernet interface
supports auto MDI/MDI-X so that a “cross-
over” or “reversing” cable will not be
required.
Ethernet Connection without PoE
As previously discussed in this guide, the
Model 374 was designed such that the
Ethernet connection will provide both data
and Power-over-Ethernet (PoE) power.
There may be situations where the asso-
ciated Ethernet switch does not provide
PoE power. In such cases an external PoE
midspan power injector can be used. If
the selected midspan power injector is
802.3af-compatible it should function cor-
rectly. Midspan units are available from a
variety of sources, including many on-line
retailers.
Headset Connection
The Model 374 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
intended for use with unbalanced dynamic
microphones. Balanced microphones
should, in most cases, also function cor-
rectly if the signal – (low) is connected to
Model 374’s mic in –/shield connection.
No support is provided for microphones
that require low-voltage “eletret,” P12
phantom, or P48 phantom powering.
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. Con-
figuration choices, discussed later in this
guide, can then be used to create the
Figure 2. Headset connection pinout chart
Model 374 User Guide Issue 2, September 2016
Studio Technologies, Inc. Page 9
desired monaural output. It’s important not
to connect together (short) pins 4 and 5
of the Model 374’s headset connector as
damage to the Model 374’s output circuit-
ry 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. The configura-
tion mode, discussed later in this guide,
can be used to create a monaural output.
It’s possible that some Beyerdynamic in-
terconnecting cable assemblies terminate
the earpiece’s left and right connections
opposite from what the Model 374 and
other broadcast equipment implements.
This may require “flipping” two wires in
a headset’s 5-pin male XLR connector
so that left and right from the Model 374
match correctly.
Dante Configuration
For audio to pass to and from the Model
374 requires that several Dante-related
parameters be configured. These configu-
ration settings will be stored in non-volatile
memory within the Model 374’s circuitry.
Configuration will typically be done with
the Dante Controller software application
which is available for download free of
charge at www.audinate.com. Versions
of Dante Controller are available to sup-
port Windows® and OS X® operating
systems. The Model 374 uses the Ultimo
4-input/4-output integrated circuit to imple-
ment the Dante architecture.
The four Dante transmitter (Tx) channels
associated with the Model 374’s Dante
interface must be assigned to the desired
receiver channels. This achieves routing
the Model 374’s four talk output audio
channels to the device (or devices) that
will be “listening” to them. Within Dante
Controller a “subscription” is the term
used for routing a transmitter flow (a
group of output channels) to a receiver
flow (a group of input channels). The num-
ber of transmitter flows associated with an
Ultimo integrated circuit is limited to two.
These can either be unicast, multicast,
or a combination of the two. If the Model
374’s transmitter channels need to be
routed to more than two flows it’s possible
that an intermediary device, such as a
rack-mounted digital signal processor unit
with more available flows, can be used to
“repeat” the signals.
The four Dante receiver (Rx) channels
associated with the Model 374’s audio
inputs also need to be routed to the de-
sired Dante transmitter channels. These
four audio signals will be sent to the Model
374’s 2-channel headphone output.
The Model 374 supports audio sample
rates of 44.1 and 48 kHz with a limited
selection of pull-up/pull-down values
available. In most cases the default will be
used and a pull-up or pull-down rate will
not be selected. The Model 374 can serve
as the clock master for a Dante network
but in most cases it will be configured to
“sync” to another device.
The Model 374 has a default Dante device
name of ST-M374 and a unique suffix. The
suffix identifies the specific Model 374 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 transmit-
ter (Tx) channels have default names of
Ch1, Ch2, Ch3, and Ch4. The four Dante
receiver (Rx) channels have default names
of Ch1, Ch2, Ch3, and Ch4. Using Dante
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Controller the default device name and
channel names can be revised as appropri-
ate for the specific application.
Model 374 Configuration
Many of the Model 374’s operating pa-
rameters can be configured to match the
needs of specific applications. The Model
374 provides four DIP switches of which
three are used to configure operating func-
tions. Two switches allow the gain of the
microphone preamplifier to be adjusted.
One switch selects if a special button back-
light mode is enabled. The fourth switch is
not utilized at this time. A software-based
configuration method is used to select the
talk button modes as well as setting the
way in which incoming audio is routed to
the headphone output channels. The DIP
switches and pushbutton switch that en-
ables configuration are accessible from
the back of the unit’s enclosure through
a rectangular opening that is located
under the top of the belt clip.
The DIP switches are connected to the
Model 374’s logic circuitry which responds
to changes by way of the application firm-
ware; no audio passes directly through the
switches. Changes made to a DIP switch
will immediately be reflected in the unit’s
operation. Changes made to the talk button
modes or headphone audio routing will be
incorporated once the configuration pro-
cess has been completed. A power cycle
is not required for configuration changes
to be recognized and implemented
Accessing the DIP Switches and
Configure Button
To access the switches and configure
button requires that the belt clip be
rotated. Normally the belt clip is secured
to the back of the enclosure using one
rivet (non-removable) and one machine
screw that has a thread pitch of 6-32. To
allow the belt clip to rotate, remove the
machine screw using a #1 Phillips head
screw driver. The belt clip should now be
able to rotate in either direction. Save the
screw so that it can be re-installed once
the desired configuration choices have
been made. Note that the threaded fas-
tener within the back of the Model 374’s
chassis has an internal locking mecha-
nism (a plastic bushing) that prevents
the belt clip’s 6-32 machine screw from
vibrating loose. So no additional method
of thread locking, such as a lock washer
or chemical compound, is necessary.
Microphone Preamp Gain
Switches SW1 and SW2 allow the gain of
the microphone preamplifier to be select-
ed. When SW1 and SW2 are in their down
(off) position 40 dB of gain is selected.
This will be appropriate for most applica-
tions. (Technically this gain is approxi-
mately equal to the gain provided within
an RTS® BP-325 analog party-line belt-
pack.) Placing SW1 to its up (on) position
while leaving SW2 in its down (off) posi-
tion selects the 43 dB gain setting. Leav-
ing SW1 to its down (off) position while
placing SW2 in its up (on) position selects
the 46 dB gain setting. This additional 3 or
6 dB of gain may be helpful in some ap-
plications, such as with headsets that have
a low microphone output level. The higher
gain settings may also be useful when
the Model 374 is going to be deployed at
events where users are not able to speak
at normal levels, e.g., sporting events
such as golf tournaments.
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