Studio Technologies 44D User manual

Copyright © 2017 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50032-1117, Issue 2
User Guide
Issue 2, November 2017
This User Guide is applicable for serial numbers
M44D-01151 and later with application firmware 2.1 and later
and Dante firmware 2.0.0 (Ultimo 3.10.1.12) and later
Also applicable to units with serial numbers
M44D-00151 to 00250; see Appendix A for details
Model 44D
Audio Interface
Dante® to and from Analog Audio

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Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 3
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 9
Configuration ................................................................ 14
Operation ...................................................................... 17
Technical Notes ............................................................. 21
Specifications ................................................................ 25
Appendix A: Original vs Updated Model 44D .............. 27

Issue 2, November 2017 Model 44D User Guide
Page 4 Studio Technologies, Inc.
Revision History
Issue 2, November 2017:
1. Documents addition of operating mode configuration (audio interface and tone
generator).
Issue 1, September 2016:
1. Initial release.

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 5
Introduction
The Model 44D Audio Interface provides
a simple yet high-performance means of
interfacing two channels of analog line-level
audio to and from applications that utilize
Dante® audio-over-Ethernet media net-
working technology. Two Model 44D units
can also provide one-to-one signal paths,
two in each direction, over a standard lo-
cal area network (LAN). In addition, the
unit supports transport of status signals or
contact closures between Model 44D units
and other compatible products. There are
two general-purpose inputs (GPI) and two
general-purpose output (GPO) on each
Model 44D.
A special operating mode allows the Model
44D to serve as a tone generator rather
than an audio interface. When configured
for the tone generator mode 1 kHz and 18
kHz sine-wave audio signals are available
in both the analog and digital domains.
The Model 44D is a fully professional prod-
uct that offers the audio quality, features,
and reliability required by 24-hour, on-air,
and commercial applications. The two
line-level audio inputs use standard 3-pin
female XLR connectors for easy interfac-
ing with balanced and unbalanced sourc-
es. The input audio signals are converted
to 24-bit digital and then transported via
the Dante interface. Two digital audio
signals arrive into the Model 44D via the
Dante interface and are then converted to
analog. Two 3-pin male XLR connectors
on the Model 44D’s back panel provide
balanced line-level outputs.
The Model 44D is designed as a bridge,
using Dante to link analog or other Dante
interfaces found on devices such as matrix
intercom systems, broadcast routers, and
audio consoles. An Ethernet connection
is all that’s required to make the Model
44D part of a sophisticated, networked
audio system. Dante audio-over-Ethernet
has found wide acceptance as an audio
“backbone” due to its ease of use, high
performance, strong interoperability, and
wide adoption by a large number of equip-
ment manufacturers. The Model 44D is a
Figure 1. Model 44D standard “throw-down” front view
Figure 2. Model 44D back view

Issue 2, November 2017 Model 44D User Guide
Page 6 Studio Technologies, Inc.
general-purpose “tool” that helps to ex-
pand Dante’s capabilities to facilities and
equipment that primarily supports signals
in the analog domain.
Careful attention to circuit design and
component selection ensures that excel-
lent audio quality is maintained. Extensive
filtering helps prevent damage or less-
than-optimal performance should DC
voltage, ESD (“static”), or strong RF sig-
nals be present on the associated analog
signals.
Configuration switches allow several
Model 44D operating parameters to be
selected. The nominal audio levels of the
line input and line output functions can
be independently selected. In this way
compatibility with SMPTE® and EBU
nominal signal levels is supported. Audio
level meters provide confirmation of sys-
tem performance during setup and opera-
tion. Two general purpose input and two
general purpose output functions allow
support for installer-selected applications,
including party-line intercom call-light
functions. Two LEDs provide a direct indi-
cation of the status of the GPO functions.
The Model 44D can be powered by Power-
over-Ethernet (PoE) or an external source
of 12 volts DC. Standard connectors
are used for the line inputs and outputs,
Ethernet, GPI/GPO, and DC power in-
terconnections. The Model 44D’s enclo-
sure has a “1/2-rack” 1U form factor and
weighs less than two pounds, making it
well suited for use in portable applications.
Alternately, using one of the optional rack-
mount front panels, one or two Model 44D
units can be mounted in a single space
(1U) of a standard 19-inch rack enclosure.
Dante Audio-over-Ethernet
Audio data is sent to the Model 44D us-
ing the Dante audio-over-Ethernet media
networking technology. Audio signals
with a sample rate of 44.1 or 48 kHz and
a bit depth of up to 24 are supported. The
two line input channels are converted to
digital and then routed to transmitter (out-
put) channels on the Dante interface. Two
transmitter (output) channels from an as-
sociated Dante-enabled source device can
be assigned to the Model 44D’s receiver
(input) channels using the Dante Controller
application. These are then converted into
analog outputs.
Applications
The most basic application for Model 44D
is for transporting analog audio signals to
and from one location to another using
the data transport resources of a local area
network — there’s really no simper means
to getting high-quality audio from “point A
to point B” and back. With standard con-
nectors and PoE power, setup can be com-
pleted in just a few minutes. This makes
Model 44D units effective in both fixed and
portable applications.
The Model 44D can also find use when an
application already supports Dante. For
example, ports on a matrix intercom system
that directly supports Dante, such as the
RTS ADAM® with OMNEO®, can be routed
to a Model 44D’s Dante output (transmitter)
and input (receiver) channels. The Model
44D will then provide two analog input and
two analog output interfaces for use in a
variety of applications. These can include
interfacing with audio inputs and outputs as-
sociated with audio consoles, providing tal-
ent cueing (IFB) feeds, and interfacing with
the audio outputs of aerial camera systems.

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 7
The Model 44D’s tone generator mode
enables the unit to create 1 kHz and 18 kHz
analog and digital sine-wave audio signals.
These are provided as a resource when
supporting remote-production (REMI) ap-
plications that use the Studio Technologies
Model 5422 Dante Intercom Audio Engine.
The tones, specifically 18 kHz, can be used
by a matrix intercom system to facilitate
creation of voice-with-tone interruptible
foldback (IFB) signals. When routed to the
Model 5422’s interrupt inputs these special-
ized IFB signals will allow excellent talent
cueing performance to occur.
Line Inputs
The Model 44D provides two analog line-
level input channels. A configuration choice
allows the nominal level of the input signals
to be +4 or 0 dBu. When configured for
+4 dBu the unit will be compatible with
SMPTE applications where the nominal
digital signal level is –20 dBFS. In the 0 dBu
configuration the line inputs are optimized
for EBU applications where the nominal
digital signal level is –18 dBFS.
The electronically balanced (differential)
input circuits are capacitor-coupled and
ESD (static) protected for reliable operation
in a variety of applications. They are also
protected from damage should a moder-
ate DC voltage be accidentally connected.
Sources can include analog I/O cards on
matrix intercom systems, audio consoles,
wireless microphone receivers, and broad-
cast routers.
Line Outputs
The Model 44D provides two analog line-
level output channels. As with the line
inputs, a configuration choice allows the
nominal level of the output signals to be
+4 or 0 dBu. This allows compatibility in
applications where SMPTE (+4 dBu =
–20 dBFS) or EBU (0 dBu = –18 dBFS)
standards may apply. The outputs are
electronically balanced, capacitor-coupled
and ESD (static) protected. The outputs
are compatible with virtually all balanced
and unbalanced inputs with an impedance
of 2 k ohms or greater.
General Purpose Inputs and
Outputs
The Model 44D allows the sending and
receiving of status signals using high-
frequency audio tones that are included
with within the Dante audio channels.
When two Model 44D units are intercon-
nected using an Ethernet network and
Dante, two status signals will be trans-
ported in each direction. Each general
purpose input (GPI) is compatible with
contact closures provided by equipment
such as matrix intercom systems or rout-
ers. A closure on a GPI on one Model 44D
unit will result in the closing (shorting) of
a solid-state relay contact on the other
Model 44D. To assist in implementing
specialized GPI and GPO applications a
source of low-current DC power is also
provided.
The GPI and GPO functions can be espe-
cially useful in party-line intercom applica-
tions where call-light signals are utilized.
Contact closures on matrix intercom
systems can be “repeated” by Model 44D
units that are located anywhere within the
associated local area network (LAN). The
Model 44D is also directly compatible with
the call-light signal support provided by
the Studio Technologies’ Model 45DC and
Model 45DR Intercom Interface units. With
a Model 44D appropriately interconnected

Issue 2, November 2017 Model 44D User Guide
Page 8 Studio Technologies, Inc.
with a matrix intercom system full call-light
support can be provided to and from RTS®
and Clear-Com® party-line intercom cir-
cuits.
Pro Audio Quality
The Model 44D’s audio circuitry was de-
signed in the spirit of professional audio
equipment rather than that found in typi-
cal broadcast or commercial audio gear.
High-performance components are used
throughout, providing low-distortion, low-
noise, and high headroom. Care was taken
so that signal integrity is maintained in both
the analog and digital domains.
Audio Meters and Status LEDs
The Model 44D provides four 5-segment
LED meters. The meters, located on the
front panel, display the level of the audio
signals associated with the two line inputs
and two line outputs. At the time of instal-
lation and setup the meters are invaluable
in helping to confirm correct operation.
During normal operation the meters offer
direct confirmation of the unit’s audio signal
levels, helping to ensure that optimal au-
dio quality is maintained. Additional LED
indicators are provided on the front panel,
offering status indications of the incoming
power and general purpose output (GPO)
functions.
Tone Generator Mode
For special applications the Model 44D can
be configured to serve as a tone generator.
Instead of functioning as an audio interface
device, the Model 44D will generate two
sine-wave audio signals, one 1 kHz and the
other 18 kHz. These signals are available
both as line-level analog and Dante digi-
tal audio (transmitter) outputs. The Model
44D’s generator mode is intended for use
with matrix intercom systems that are used
with the Studio Technologies’ Model 5422
Dante Intercom Audio Engine. The 18 kHz
signal will be connected to a matrix inter-
com system using either analog or Dante
inputs. The matrix intercom system will be
configured such that it will combine voice
audio with the 18 kHz tone to create spe-
cialized IFB signals. These voice-with-tone
signals will be routed, by way of an audio
transport system, to Model 5422 interrupt
inputs associated with tone operated (TOX)
IFB channels. The Model 5422 will detect
the 18 kHz tone and “trigger” the associ-
ated IFB function. In this way high-perfor-
mance IFB functions can be implemented
for REMI (remote-production) applications.
The 1 kHz tone that is generated by the
Model 44D is provided for general-purpose
use. It can also be used as a troubleshoot-
ing resource when configuring matrix
intercom systems for tone-operated (TOX)
IFB operation. Both the 1 kHz and 18 kHz
tones are precise in terms of frequency and
level accuracy, as well as being very low in
harmonic distortion.
Ethernet Data, PoE, and DC
Power Source
The Model 44D connects to a data network
using a standard 100 Mb/s twisted-pair
Ethernet interface. The physical intercon-
nection is made by way of a Neutrik®
etherCON RJ45 connector. While compat-
ible with standard RJ45 plugs, etherCON
allows a ruggedized and locking intercon-
nection for harsh or high-reliability environ-
ments. The Model 44D’s operating power
can be provided by way of the Ethernet
interface using the Power-over-Ethernet
(PoE) standard. This allows fast and

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 9
efficient interconnection with the associ-
ated data network. To support PoE power
management, the Model 44D’s PoE inter-
face reports to the power sourcing equip-
ment (PSE) that it is a class 1 (very low
power) device. The unit can also be pow-
ered using an external source of 12 volts
DC. Four LEDs on the back panel display
the status of the network connection,
Dante interface, and PoE power source.
Simple Installation
The Model 44D uses standard connectors
to allow fast and convenient interconnec-
tions. An Ethernet signal is connected
using a Neutrik etherCON RJ45. If Power-
over-Ethernet (PoE) is available operation
will commence immediately. An external
12 volt DC power source can also be con-
nected by way of a 4-pin XLR connector.
Line input and line output connections are
made using 3-pin XLR connectors. A 9-pin
female D-subminiature (DE-9F) connec-
tor provides access to the two GPI, two
GPO, and auxiliary DC output functions.
The Model 44D is housed in a rugged yet
lightweight aluminum enclosure that is de-
signed to be “field tough.” It can be used
as a standalone portable unit, supporting
what’s known in the broadcast world as
“throw-down” applications. Rack-mount
options are also available allowing one or
two units to be mounted in one space (1U)
of a standard 19-inch rack enclosure.
Future Capabilities and
Firmware Updating
The Model 44D was designed so that its
capabilities 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.
To implement the Dante interface the
Model 44D uses Audinate’s Ultimo™
integrated circuit. The firmware in this
integrated circuit can be updated via the
unit’s Ethernet connection, helping to en-
sure that its capabilities remain up to date.
Getting Started
In this section signal interconnections will
be made using the variety of connectors
located on the Model 44D’s back panel.
Connections to the two line inputs and two
line outputs will be made using 3-pin male
and female XLR connectors. An Ethernet
data connection will be made using either
a standard RJ45 patch cable or an ether-
CON protected RJ45 plug. A 4-pin XLR
connector allows the connection of an
external source of 12 volts DC. Interfacing
with the GPI, GPO, and auxiliary DC out-
put functions can be made using a 9-pin
female D-subminiature (DE-9F) connector.
System Components
Included in the shipping carton are the
Model 44D Interface and a printed copy
of this guide. If a rack-mount front panel
is going to be used as part of the installa-
tion it will typically be shipped in a sepa-
rate carton. If the installation or specific
application requires an external source of
12 volts DC it needs to be provided sepa-
rately. A compatible power supply, the
Studio Technologies’ PS-DC-02, is avail-
able as an option.
Locating the Model 44D
The location of the Model 44D will primar-
ily depend on being within the 100-meter

Issue 2, November 2017 Model 44D User Guide
Page 10 Studio Technologies, Inc.
(325-foot) twisted pair Ethernet cable limi-
tation. But that can be overcome by us-
ing a fiber-optic interconnect between the
Model 44D-related Ethernet switch and the
other Ethernet switches in the local-area-
network (LAN). The analog line input and
line output connections, typically being
wired as a differential (balanced) pair with
shield, can support lengthy cable runs
with negligible impact on audio quality.
Protecting the Enclosure
The Model 44D is shipped as a self-
contained unit suitable for portable use
or placement in a semi-permanent loca-
tion. Installed on the bottom of the chassis
are screw-on “bump on” protectors (also
known as “rubber feet”). These are useful
if the unit is going to be placed on sur-
faces where scratching of either the Model
44D or the surface material could take
place. The “feet” can be removed, without
the use of a tool, when rack- or custom-
mounting the unit.
Rack Mounting the Model 44D
For permanent or mobile applications it
might be desirable to mount one or two
Model 44D units into one space (1U)
of a 19-inch rack enclosure. A range of
rack-mount front panels, each purchased
separately, are available from Studio Tech-
nologies. The following provides details
on how to install Model 44D units to these
panels.
To attach a Model 44D unit to the single-
unit rack-mount panel, begin the process
by using a 5/64-inch hex wrench to re-
move the four 6-32 thread button-head
cap screws that hold the standard front
panel to the chassis. Note that the screws
might be quite tightly affixed. Ensure that
a good-quality hex wrench is used and
press and hold it firmly into each screw
head while turning counterclockwise. Un-
less this recommendation is followed the
hex wrench could “cam out” and the head
could be damaged (“stripped”).
Using the screws that were just removed,
attach the rack-adapter front panel to the
Model 44D’s chassis. To prevent damage
care is required when aligning the front
panel with the LEDs that protrude slightly
through both the Model 44D’s chassis
and front panel. Tighten the four screws
only after a careful inspection ensures
that all of the LEDs protrude through the
front panel without interference. To allow
vertical clearance in the associated rack,
remove the four “bump on” protectors
from the bottom of the chassis. They
are removed by using the fingers to
rotate them counterclockwise; no tool
is required. It’s probably a good idea to
carefully protect and store the standard
front panel, along with the “bump on”
protectors, for possible later use.
Mounting a Model 44D to a dual-unit rack-
mount panel follows the same procedure
but will apply to two units. Store both of
the removed standard front panels and
the eight “bump on” protectors for possi-
ble later use. Note that on the rack-panel’s
graphics the Model 44D unit that’s on the
left is designated as A while the unit on
the right is designated as B. This is pro-
vided so that each can be easily identified
during installation, troubleshooting, and
operation.
Once the desired one or two Model 44D
units have been installed in a rack-mount
front panel, the assembly can be mounted
into the designated equipment rack.
One space (“1U” or 1.75 vertical inches)

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 11
in a standard 19-inch equipment rack
is required. Secure the front panel into
the equipment rack using two mounting
screws per side.
Ethernet Connection
An Ethernet connection that supports
100BASE-TX (100 Mb/s over twisted-pair)
is required for the Model 44D’s Dante
audio-over-Ethernet connectivity. A
10BASE-T connection is not sufficient
for Model 44D operation. A 1000BASE-T
(“GigE”) connection is not supported
unless it can automatically “fall back” to
100BASE-TX operation. An Ethernet con-
nection that supports Power-over-Ethernet
(PoE) is preferred as it will provide both
data and operating power for the Model
44D. To support power management
functionality on an associated PoE switch
(PSE) the Model 44D will enumerate itself
as a PoE class 1 (very low power) device. If
PoE is not available an external 12 volt DC
power source can be connected. This will
be discussed in a later sub-section of the
guide.
The 100BASE-TX Ethernet connection
is made by way of a Neutrik etherCON pro-
tected RJ45 connector that is located on
the back panel of the Model 44D. This al-
lows connection by way of a cable-mount-
ed etherCON plug or a standard RJ45
plug. The Model 44D’s Ethernet interface
supports auto MDI/MDI-X and, as such,
using a crossover or “reversing” cable will
not be required.
External 12 Volt DC Input
An external source of 12 volts DC can be
connected to the Model 44D by way of a
4-pin male XLR connector which is located
on the back panel. While the requirement
for the external source is nominally 12
volts, correct operation will take place
with any source that has a range of 10 to
18 volts DC. The Model 44D requires 300
milliamperes maximum at 12 volts DC for
correct operation. The DC source should
be terminated to a 4-pin female XLR con-
nector with pin 1 negative (–) and pin 4
positive (+). Purchased as an option, the
PS-DC-02 power supply is available from
Studio Technologies. Its AC mains input
allows connection to a 100-240 volts,
50/60 Hz source and its 12 volt DC, 1.5
amperes maximum output is terminated
on a 4-pin female connector.
As previously discussed in this guide, an
Ethernet connection that provides Power-
over-Ethernet (PoE) can serve as the
Model 44D’s power source. Alternately,
an external 12 volt DC source can be
connected. For redundancy, both PoE and
an external 12 volt DC source can be con-
nected at the same time. If both PoE and
an external 12 volt DC source are connect-
ed, power will be drawn only from the PoE
supply. If the PoE source becomes inoper-
ative the 12 volt DC source will provide the
Model 44D’s power with no interruption in
operation. (Of course, normal operation
will cease if both PoE and data transport
fails on the Ethernet connection.)
Line Inputs
The Model 44D provides two line inputs
that are intended for connection to line-
level analog audio signal sources associ-
ated with professional audio and video
equipment. It’s expected that the nominal
level of the analog sources will either
be +4 dBu for SMPTE applications or
0 dBu for EBU applications. (Refer to the
Configuration section of this guide for

Issue 2, November 2017 Model 44D User Guide
Page 12 Studio Technologies, Inc.
details.) Commonly-used sources could
include analog I/O ports on broadcast
matrix intercom systems, audio consoles,
video storage and playback systems,
wireless microphone receivers, and audio
testing equipment. The circuitry associat-
ed with the line inputs is analog, electroni-
cally balanced, capacitor coupled, with an
impedance of 20 k ohms.
Two 3-pin female XLR connectors, located
on the Model 44D’s back panel, are used
for interfacing with the source signals.
Prepare 3-pin male XLR mating connec-
tors such that pin 2 is signal high (+),
pin 3 is signal low (–), and pin 1 is com-
mon/shield. It’s also highly possible that
an unbalanced source will interface cor-
rectly. With an unbalanced source begin
by connecting signal high (+) to pin 2 and
signal low/shield (–) to both pins 1 and 3.
If this results in hum or noise, next try con-
necting signal high (+) to pin 2 and signal
low/shield (–) only to pin 3; leave pin 1
unconnected (“floating”).
If the Model 44D has been configured to
operate in the tone generator mode the
two analog line inputs will not be active.
As such, no connections should be made
to either line input channel 1 or line input
channel 2.
Line Outputs
The Model 44D provides two line outputs.
These analog outputs are designed for
general-purpose use which could include
connecting to analog inputs on devices
including matrix intercom systems, trans-
mitters associated with wireless in-ear
monitors, audio consoles, or amplified
speakers. The circuitry associated with the
line outputs is analog, capacitor-coupled,
and has a source impedance of 200
ohms. It will perform optimally when driv-
ing loads of 2 k (2000) ohms or greater.
The nominal level of the line outputs is
configurable to be either +4 dBu or 0 dBu,
corresponding to SMPTE or EBU applica-
tions. (Refer to the Configuration section
of this guide for details.)
Two 3-pin male XLR connectors, located
on the Model 44D’s back panel, are
provided for interfacing the line outputs
with associated equipment. Prepare
3-pin female XLR mating connectors
such that pin 3 is signal high (+), pin 2
is signal low (–), and pin 1 is common/
shield. To connect to an unbalanced load
use pin 2 as signal high (+) and pin 1 as
low/shield; do not connect anything to
pin 3. Do not short pins 3 to pin 1 on the
Model 44D’s line output connectors as it
will stress the output circuitry.
General Purpose Inputs (GPI)
The Model 44D provides two general-
purpose input functions that are referred
to as GPI 1 and GPI 2. These functions
allow transport of the status of relay con-
tacts or open-collector logic signals. The
Model 44D’s GPI inputs use logic circuitry,
“pulled up” to 3.3 volts DC by way of resis-
tors, which are active whenever they are
brought to their logic low state. While the
GPI input circuitry is protected from over-
current and static discharge (ESD), care
should be taken to minimize the chance
that “nasty” signals can reach them.
The GPI inputs are active only when held
in their low state; they can’t be configured
to change state (“latch”) in response to
a logic pulse or momentary closure. Pins
on a 9-pin female D-subminiature con-
nector (DE-9F) are used for interfacing
with the GPI inputs and system common

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 13
connections. This connector is located on
the Model 44D’s back panel. A GPI is only
active when its corresponding pin is con-
nected to system common. GPI 1 is acces-
sible on pin 3 and GPI 2 on pin 4. System
common is available on pins 8 and 9. Refer
to Figure 3 for connection details.
Connections made to the analog line out-
puts will be the same whether the Model
44D has been selected to operate in the
audio interface mode or in the tone genera-
tor mode. In the latter mode a continuous
1 kHz sine-wave tone will be present on
line output channel 1 and a continuous
18 kHz sine-wave tone will be present on
line output channel 2. The nominal level
of both signals will be +4 dBu.
General Purpose Outputs
(GPO)
The Model 44D provides two general-
purpose output functions that are referred
to as GPO 1 and GPO 2. These functions
provide contact closures that respond to
trigger signals transported over the Dante
input (receiver) audio paths. The trigger
signals are in the form of high-frequency
audio tones (typically 20 kHz) that travel
along with the normal audio signals. The
normally-open (not shorted) contact clo-
sures are isolated from system common.
They are provided by solid-state relay
contacts which are intended to control
low-voltage/low-current DC functions. The
contacts are rated for a maximum current
of 400 milliamperes and a maximum of
60 volts DC or AC. They are not intended
for direct connection to AC mains (high-
voltage AC signals.).
Pins on a 9-pin female D-subminiature con-
nector (DE-9F), located on the Model 44D’s
back panel, allow interfacing with the GPO
connections. Two connections are provided
for each GPO, pins 1 and 6 for GPO 1 and
pins 2 and 7 for GPO 2. Refer to Figure 3
for connection details.
Auxiliary DC Output
A source of low-voltage, low-current DC
is available for support of special applica-
tions that use the GPO functions. The auxil-
iary DC output has a nominal voltage of
12 and is referenced to system common.
During normal operation the output can
range from 10 to 18 volts DC if an external
power source is connected to the Model
44D and is providing operating power.
Circuitry associated with the auxiliary DC
output limits the maximum current to 25
milliamperes. The auxiliary DC output is ac-
cessible by way of pin 5 of the 9-pin female
D-subminiature (DE-9F) connector that’s
located on the Model 44D’s back panel.
System common is provided on pins 8 and
9. Refer to figure 3 for connection details.
Figure 3. GPI, GPO, and Auxiliary DC Output
connections
Pin Function
1 GPO 1-A
2 GPO 2-A
3 GPI 1
4 GPI 2
5 Aux DC Out
6 GPO 1-B
7 GPO 2-B
8 COM
9 COM
Note:
Connector type on Model 44D is a 9-pin
female D-subminiature (DE-9F). Installer
must provide a 9-pin male D-subminiature
(DE-9M). Connector uses 4-40 threaded
inserts for locking with mating plug.

Issue 2, November 2017 Model 44D User Guide
Page 14 Studio Technologies, Inc.
The exact use of the auxiliary DC output will
depend on the needs of the specific appli-
cations and the capabilities of the installer.
The auxiliary DC output can, for example,
be connected in series with a GPO’s relay
contact and used to directly light a status
LED, enable an optical coupler, or provide
a “GPO active” voltage output. Be careful
to limit the load placed on the auxiliary out-
put. Its circuitry will limit the current to 25
milliamperes but keeping it from reaching
that maximum value is a good idea.
Configuration
Back-Panel DIP Switches
A 4-position DIP switch assembly, labeled
Config, is located on the Model 44D’s
back panel. The switches are used to set
operating parameters, including line input
nominal level, line output nominal level,
low-pass filter on/off status, and operating
mode.
Line Input Nominal Level
Switch SW1 is used to configure the nomi-
nal level of the Model 44D’s two line input
channels. When SW1 is in its off (down)
position the line inputs are configured such
that connecting an analog signal at a level
of +4 dBu will result in a digital signal at
–20 dBFS being present on the corre-
sponding Dante output (transmitter) chan-
nel. This would allow compatibility with
SMPTE standards. When SW1 is in its up
(on) position connecting an analog signal
at a level of 0 dBu will result in a digital
signal at –18 dBFS being present on the
corresponding Dante output channel. This
is compliant with EBU standards.
The choices provided by SW1 are primar-
ily intended to allow the Model 44D’s line
input gain structure to be matched to the
needs of specific applications. Most North
American (SMPTE) applications will follow
+4 dBu in the analog domain being equal
to –20 dBFS in the digital domain. While in
Europe (EBU) it would be typical in mod-
ern installations for 0 dBu (analog) to be
equal to –18 dBFS (digital).
But SW1 can be used as a coarse level
adjustment function if necessary. In a
SMPTE-compliant installation (+4 dBu =
–20 dBFS) setting SW1 to its on (up) posi-
tion will provide a 6 dB increase in input
sensitivity. This could be useful if the aver-
age level of the signal connected to the
line inputs was a little low. And in an EBU
application setting SW1 to its off (down)
position would provide a 6 dB decrease
in input sensitivity. This could be useful if
the analog signals connected to the line
inputs were especially “hot.”
Line Output Nominal Level
Switch SW2 is used to configure the
nominal level of the Model 44D’s two line
output channels. When SW2 is in its off
(down) position the line outputs are con-
figured such that a Dante input (receiver)
channel with a signal level of –20 dBFS
will result in an analog signal at the cor-
responding line output channel having a
level of +4 dBu. This configuration would
Figure 4. Analog inputs nominal level
configuration switch

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 15
allow compatibility with SMPTE digital-to-
analog level-relationship standards. When
SW2 is in its up (on) position a Dante input
(receiver) with a signal level of –18 dBFS
will result in an analog signal at the cor-
responding line output channel having a
level of 0 dBu. This relationship will make
the line output compliant with EBU stan-
dards.
The choices provided by SW2 are primar-
ily intended to allow the Model 44D’s line
output gain structure to match the needs
of specific applications. Most North Ameri-
can (SMPTE) applications will follow
–20 dBFS in the digital domain being equal
to +4 dBu in the analog domain. While in
Europe (EBU) it would be typical in mod-
ern installations for –10 dBFS (digital) to
be equal to 0 dBu (analog).
SW2 can be used as a coarse level adjust-
ment function if necessary. In a SMPTE-
compliant installation (–20 dBFS =+4
dBu) setting SW2 to its on (up) position will
provide a 6 dB decrease in input sensitiv-
ity. This could be useful if it’s desirable for
the average level of the line output signals
to be less than typical. This can be use-
ful when a true “+4 dBu” output is simply
too “hot.” And in an EBU application set-
ting SW2 to its off (down) position would
provide a 6 dB increase in input sensitivity.
This could be useful if the average level
on the Dante input (receiver) channels is
lower than expected and a “hotter” analog
output is desirable.
Low-Pass Filters
Switch SW3 allows a low-pass filter func-
tion to be enabled or disabled as desired.
The function consists of four digital filters,
two applying to the audio signals from the
line inputs and two applying to the signals
destined for the line outputs. When active
the
filters will eliminate most of the audio con-
tent above 10 kHz that enters the Model
44D by way of the line inputs and exits the
Model 44D by way of the line outputs.
When SW3 is in its off (down) position the
low-pass filters are disabled. Full band-
width audio signals will past through the
Model 44D’s line inputs and line outputs.
When SW3 is in its on (up) position the
low-pass filters will be enabled. Enabling
the low-pass filters can improve the per-
formance and possibly the intelligibility of
audio signals that consist mainly of voice
content. In this case audio content in the
extend high-frequency range will typi-
cally provide little enhancement to system
performance and can often contain extra-
neous nose or other unwanted artifacts.
Also, in situations where a Model 44D’s
GPO functions are used, enabling the low-
pass filters will prevent the signaling tones
(typically
Enabled
Disabled
SW3 – 10 kHz Low-Pass Filter
1 2 3 4
ON
1 2 3 4
ON
Figure 6. 10 kHz low-pass filter configuration
switch
Figure 5. Analog outputs nominal level
configuration switch

Issue 2, November 2017 Model 44D User Guide
Page 16 Studio Technologies, Inc.
20 kHz) from being part of the signals that
are presented on the line outputs.
Operating Mode
Switch SW4 is used to configure the
Model 44D’s operating mode. When SW4
is in its off (down) position the Model 44D
functions as an audio interface. This would
be considered its normal mode of opera-
tion. When SW4 is in its on (up) position
the tone generator mode is selected. In
the tone generator mode the Model 44D
generates 1 kHz and 18 kHz sine-wave
tones. Analog output 1 and Dante trans-
mitter (output) channel 1 will have a con-
tinuous source of 1 kHz present. Analog
output 2 and Dante transmitter (output)
channel 2 will have a continue source of
18 kHz present.
The two Dante receiver channels will be
assigned to the desired Dante transmitter
channels on other devices. The two trans-
mitter channels associated with the Model
44D’s Dante interface must be assigned
to the desired destinations (Dante receiver
channels on associated devices). This will
typically be done with the Dante Controller
software application which is available for
download free of charge at www.audinate.
com. Versions are available to support
Windows® and OS X® operating systems.
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). Note that
as of the writing of this guide the Ultimo in-
tegrated circuit limits the number of Dante
flows to two. These can either be unicast,
multicast, or a combination of the two.
The Model 44D has a default Dante device
name of ST-M44D followed by a unique
suffix. The suffix identifies the specific Mod-
el 44D that is being configured. The suffix’s
actual alpha and numeric characters relate
to the MAC address of the Ultimo inte-
grated circuit that’s present in the specific
Model 44D. The two Dante receiver (input)
channels have the default names of Ch1
and Ch2. The two Dante transmitter (out-
put) channels also have the default names
of Ch1 and Ch2. Using Dante Controller
these names can be revised as appropriate
for the specific application.
The Model 44D supports audio sample
rates of 44.1 and 48 kHz along with several
pull-up/pull-down values. The desired
configuration can be made using the
Dante Controller software application.
The Model 44D can serve as the clock
master for a Dante network but in most
cases that would not be optimal.
SW4 – Operating Mode
1 2 3 4
ON
1 2 3 4
ON
Tone Generator
Audio Interface
Figure 7. Operating mode configuration switch
Dante Configuration
To integrate the Model 44D into an audio
interface application several Dante-
related parameters can be configured. At
a minimum, signals must be routed to the
two Dante input (receiver) channels and
from the two output (transmitter) channels.
The configuration settings will be stored
in non-volatile memory within the Model
44D’s circuitry. As such, power-down and
power-up activities will not impact the
unit’s settings. The Model 44D uses the
Ultimo 2-input/2-output integrated circuit
to implement the Dante architecture.

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 17
Switch SW4, located on the back panel, is
used to configure Model 44D’s operating
mode. When selected for the tone gen-
erator mode (SW4 on (up)) normal audio
interface operation will not take place.
The unit’s internal processor will generate
two sine-wave audio signals (tones). The
two Dante transmitter (output) channels
should be assigned to the desired destina-
tions. The two Dante transmitter (output)
channels will have the default names of
1kHz and 18kHz. Signals routed to the
two Dante input (receiver) channels will
not cause any Model 44D activity to take
place. The two Dante receiver (input)
channels will have the defaults names of
Ch1–Inactive and Ch2–Inactive.
Operation
At this point the Model 44D should have
its Ethernet, line input, line output, and
GPI/GPO connections implemented as
desired for the application. Depending on
the capabilities of the Ethernet connection
an external 12 volt DC power connection
may have also been made. The two Dante
transmitter (output) channels and two
Dante receiver (input) channels should
have been routed using the Dante Control-
ler software application. Normal operation
of the Model 44D can now begin.
The Model 44D is designed for continuous
operation with no adjustments required.
Maintaining the correct signal levels com-
ing into the line inputs and Dante receiver
channels is important. This will ensure
that proper signal levels are presented
to the Model 44D’s circuitry and associ-
ated equipment, leading to optimal audio
performance. The audio level meters and
GPO status LEDs will provide assistance
in confirming that correct operation is
taking place.
Initial Operation
The Model 44D will begin its initial func-
tioning a few seconds after its power
source is connected. As previously dis-
cussed, the unit’s power source can be
provided by Power-over-Ethernet (PoE)
or an external source of 12 volts DC. If
both are connected the PoE source will
power the unit. Should PoE power sub-
sequently no longer be available, uninter-
rupted operation will continue using the
external 12 volt DC source. (This will prob-
ably prove to be a “hollow” victory since a
loss of PoE will probably also mean a loss
of the required Ethernet data connection!)
Upon Model 44D power up the status
LEDs will light in various manners. The
PoE, Dante, and Ethernet status LEDs,
located on the back panel, will light in
various ways. On the front panel the input
power, GPO status, and audio level meter
LEDs will light in a sequence. Once the
test sequence has completed the two
columns of level meter LEDs associated
with the line outputs will momentarily dis-
play the version number of the unit’s ap-
plication firmware (embedded software).
Details on how to “read” the version num-
ber are provided in the Technical Notes
section of this guide.
The Model 44D will now begin normal op-
eration. The way in which the back-panel
LINK/ACT, SYS, SYNC, and PoE LEDs
light will depend on the characteristics
of the connected Ethernet signal and the
configuration of the unit’s Dante interface.
Details will be covered in the next para-
graph. The user is presented on the front

Issue 2, November 2017 Model 44D User Guide
Page 18 Studio Technologies, Inc.
panel with two input power status LEDs,
two GPO status LEDs, and four 5-segment
LED audio level meters. These resources
are simple to understand and should prove
to be useful as will be highlighted in the
following paragraphs.
Ethernet, PoE, and Dante
Status LEDs
Four status LEDs are located below the
etherCON connector on the Model 44D’s
back panel. The LINK/ACT LED will light
green whenever an active data connec-
tion to a 100 Mb/s Ethernet network has
been established. It will flash on and off
in response to data packet activity. The
PoE LED will light green whenever Power-
over-Ethernet (PoE) associated with the
connected Ethernet signal is providing
operating power for the Model 44D. The
SYS and SYNC LEDs display the operating
status of the Dante interface and associ-
ated audio-over-Ethernet network. The SYS
LED will light red upon Model 44D power
up to indicate that the Dante interface is not
ready. After a short interval it will light green
to indicate that it is ready to pass audio
data with another Dante device. The SYNC
LED will light red when the Model 44D is
not synchronized with a Dante network. It
will light solid green when the Model 44D
is fully synchronized with a Dante network
and an external clock source (timing refer-
ence) is being received. It will slowly flash
green if this specific Model 44D is serving
as the clock master for the Dante network.
How to Identify a Specific
Model 44D
The Dante Controller software application
offers an identify command that can be
used to help locate a specific Model 44D.
When identify is selected for a specific unit
its audio level meter LEDs will light in a
unique pattern. In addition, the SYS and
SYNC LEDs, located directly below the
etherCON connector on the back panel,
will slowly flash green. After a few seconds
the LED identification patterns will cease
and normal Model 44D level meter and
Dante status LED operation will again take
place. Audio performance will not be im-
pacted by the use of the identify command.
As such it’s perfectly acceptable to use
the identify command any time it would be
useful.
Line Inputs
The Model 44D’s two line inputs are elec-
tronically balanced (differential), capacitor
coupled, with a nominal impedance of 20 k
ohms. The nominal analog level of signals
presented to the line inputs should match
the Model 44D’s configuration. If the nomi-
nal input level is configured for –20 dBFS
this will equate to a nominal analog input
level of +4 dBu. If the nominal input level
is configured for –18 dBFS this will equate
to a nominal input level of 0 dBu. As such,
if the nominal level of the Dante output
(transmitter) channels is 6 dB different than
expected, either high or low, a user should
confirm that the Model 44D’s input configu-
ration has been set correctly.
The line input circuitry is protected from
damage should a moderate DC voltage
be accidentally connected. For example,
no damage will occur if a powered analog
party-line intercom circuit (typically 28 to
32 volts DC from 3-pin XLR pin 2 to pin 1)
be accidentally connected. This protection
would also be effective should P48 phan-
tom power associated with a microphone
signal be accidentally connected.

Model 44D User Guide Issue 2, November 2017
Studio Technologies, Inc. Page 19
The frequency response of the line inputs
will depend on the configuration of the
low-pass filter function. If the filter is en-
abled most energy above 10 kHz will be
removed. This will be effective for voice-
applications such as intercom or talent
cueing (IFB). If support for high-quality,
full-bandwidth audio is necessary ensure
that the low-pass filter function has been
disabled. This will also apply if 20 kHz
nominal “call light” or signaling tones
need to pass through the Model 44D’s
line input to the Dante output (transmitter)
channels.
Line Outputs
The line outputs are electronically bal-
anced (differential) and intended to be
connected to various analog inputs with
nominal impedances of 2 k (2000) ohms
or greater. The nominal analog level of
signals present on the line outputs will
depend on the Model 44D’s configuration.
If the nominal output level is configured
for –20 dBFS this will equate to a nominal
analog output level of +4 dBu. If the nomi-
nal output level is configured for –18 dBFS
this will equate to a nominal output level of
0 dBu. As such, if the nominal analog out-
put level is 6 dB different than expected,
either high or low, a user should confirm
the Model 44D’s configuration.
No special precautions are necessary
when using the line outputs in settings
where a variety of signals are present. As
with the line inputs, the line output circuitry
is protected from damage. For example,
no damage will occur if a powered analog
party-line intercom circuit or a microphone
signal with P48 phantom power present
be accidentally connected.
Similar to the line inputs, the frequency
response of the line output will depend
on the configuration of the low-pass filter
function. If the filter is enabled most en-
ergy above 10 kHz will be removed. This
will be effective for voice-applications such
as intercom or talent cueing (IFB). If sup-
port for high-quality, full-bandwidth audio
is necessary ensure that the low-pass
filter function has been disabled. This will
also apply if 20 kHz nominal “call light”
or signaling tones need to pass from the
Model 44D’s Dante receiver inputs to the
line outputs.
Level Meters
The Model 44D contains four 5-segment
LED level meters, two associated with the
line inputs and two associated with the
line outputs. The meters are provided as
a support aid during installation, configu-
ration, operation, and troubleshooting.
General
The meters are organized into two groups
with one group representing the two line
inputs and the second group represent-
ing the two line outputs. The two meters
associated with the line inputs are cali-
brated in reference to the configuration of
the nominal level of the line inputs. When
configured for +4 dBu nominal a meter’s
0 LED lighting will indicate that an analog
signal with a level of +4 dBu is present on
the associated line input. This would trans-
late to an output (transmitter) level of
–20 dBFS being sent to the Dante net-
work. When the line inputs are configured
for 0 dBu nominal a meter’s 0 LED lighting
will indicate that a signal with a 0 dBu is
present on the line input and the corre-
sponding Dante output (transmit) level
will be –18 dBFS.

Issue 2, November 2017 Model 44D User Guide
Page 20 Studio Technologies, Inc.
Similar to the line inputs, the two meters
associated with the line outputs are cali-
brated in reference to the configuration
of nominal level of the line outputs. When
configured for +4 dBu nominal a meter’s
0 LED lighting will indicate that a Dante in-
put (receiver) level of –20 dBFS is present
along with a corresponding signal on the
line output with a level of +4 dBu. When
the line outputs are configured for a 0 dBu
nominal level a meter’s 0 LED lighting will
indicate that a Dante input (receiver) level
of –18 dBFS is present. And the corre-
sponding analog output signal present on
the line output will have a level of 0 dBu.
Each level meter contains four green LEDs
and one yellow LED. The four green LEDs
indicate audio signal levels at or below
the selected nominal level (+4 dBu or 0
dBu). The top LED is yellow and indicates
a signal that is 6 dB or greater than the
selected nominal level. An audio signal
that causes the yellow LED to light doesn’t
necessarily indicate an excessive level
condition, but it does provide a warning
that at some stage reducing the signal
level of the source may be prudent. Typi-
cal operation with normal signal levels
should find the meters lighting near their
“0” point. Signal peaks may cause the
yellow LEDs to flash. But a yellow LED
that lights fully during normal operation
will typically indicate excessive signal level
and/or a configuration problem with asso-
ciated Dante-enabled equipment.
Non-Optimal Signal Levels
If the meters consistently display levels
that are lower or higher than 0 it’s pos-
sible that a configuration issue exists. This
would typically be related to an incorrect
Model 44D line input or line output con-
figuration or an incorrect setting on the
equipment associated with the Model 44D.
With a digital matrix intercom system pro-
viding the Dante input signal this problem
could be due to an incorrect configuration
having been made to its specific channel
or port. For example, the RTS® ADAM
system has a published nominal level of
+8 dBu, but it’s not clear how this trans-
lates into a digital audio level on an asso-
ciated OMNEO® (Dante-compatible) port.
Using its configuration software it’s most
likely possible to set the nominal level of
intercom key panels or ports to something
different than +8 dBu. The best solution in
this case would be to adjust the associat-
ed OMNEO (Dante-compatible) port such
that it results in a nominal level that match-
es the Model 44D’s configuration. So, for
example, if the Model 44D is configured
for +4 dBu nominal input levels then the
associated OMNEO (Dante) transmitter
channels should be set up to be the same.
This should lead to the optimal perfor-
mance of the Model 44D and the associ-
ated intercom system.
GPI/GPO
Whether or not the general-purpose inputs
(GPI) and general-purpose outputs (GPO)
functions are implemented will depend on
the needs of the specific application. If the
appropriate connections are made using
the 9-pin D-subminiature connector either
or both functions can be utilized. No user-
action is required for the functions to be
active. There is no user indication when a
GPI input has been activated. Two front-
panel LEDs will indicate when a signal on
the Dante receiver input has been recog-
nized as a GPO.
A typical application might find two Model
44D units communicating with each other.