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Studio Technologies Model 44D Dante Audio Interface

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 networking technology. Two Model 44D units can also provide one-to-one signal paths, two in each direction, over a standard local 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.

The Model 44D is a fully professional product 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 interfacing with balanced and unbalanced sources. 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.

Features:

  • Dante audio-over-Ethernet technology 
  • Input and output level metering 
  • Selectable input and output nominal levels 
  • Excellent audio quality 
  • GPI/GPO support 
  • PoE and 12 Vdc powering 
  • Standard connectors 
  • Table-top, portable, or optional rack-mount use


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 equipment manufacturers. The Model 44D is a general-purpose "tool" that helps to expand 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 excellent audio quality is maintained. Extensive filtering helps prevent damage or less-than-optimal performance should DC voltage, ESD ("static"), or strong RF signals 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 system performance during setup and operation. 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 indication 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 interconnections. The Model 44D's enclosure 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.

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 connectors and PoE power, setup can be completed 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 associated with audio consoles, providing talent cueing (IFB) feeds, and interfacing with the audio outputs of aerial camera systems.

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 moderate DC voltage be accidentally connected. Sources can include analog I/O cards on matrix intercom systems, audio consoles, wireless microphone receivers, and broadcast 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 interconnected using an Ethernet network and Dante, two status signals will be transported in each direction. Each general purpose input (GPI) is compatible with contact closures provided by equipment such as matrix intercom systems or routers. 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 especially useful in party-line intercom applications 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 with a matrix intercom system full call-light support can be provided to and from RTS® and Clear-Com® party-line intercom circuits.

Pro Audio Quality
The Model 44D's audio circuitry was designed in the spirit of professional audio equipment rather than that found in typical 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 installation 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 audio 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.

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 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. 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 efficient interconnection with the associated data network. To support PoE power management, the Model 44D's PoE interface reports to the power sourcing equipment (PSE) that it is a class 1 (very low power) device. The unit can also be powered 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 interconnections. 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 connected 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) connector 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 designed 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 ensure that its capabilities remain up to date.