The Model 5401 Dante Master Clock provides precise timing signals for applications that utilize the Dante® audio-over-Ethernet media networking technology. The unit implements a high-performance IEEE 1588 precision time protocol (PTP) server, compatible with the requirements of Dante and capable of simultaneously supporting the timing needs of up to hundreds of Dante-compatible devices. As expected, the Model 5401 provides the PTP v1 (IEEE® 1588-2002) compatibility that's required by Dante. In addition, the unit supports PTP v2 (IEEE 1588-2008) for AES67 applications. A word clock output provides a timing reference for use by external devices. The Model 5401 also generates up to eight sine-wave audio tones on Dante transmit (output) channels, useful during audio network installation, maintenance, and operation. A sync input connection allows the Model 5401's internal oscillator to synchronize with a variety of timing reference signals.

The Model 5401 is suitable for use in fixed and mobile broadcast facilities, post-production studios, commercial and educational theater environments, and entertainment applications. Only power and one or two Ethernet network connections are required for full operation. Using Dante’s inherent capabilities two Model 5401 units can serve in primary and secondary master clock roles for redundant operation.

An integral web server allows fast and flexible monitoring and configuration of the Model 5401's master clock, tone generation, and networking performance. Front-panel indicators, an LCD display, and pushbutton switches provide personnel with direct access to key operating parameters. Updating of the Model 5401's operating software can be easily performed using the integrated FTP (file-transfer protocol) client. The unit's dual Gigabit Ethernet (GigE) network interfaces allow support for redundant Dante operation. All software files and configuration parameters are stored in non-volatile memory. The Model 5401 can be powered by 100-240 V, 50/60 Hz mains or a source of 12 volts DC. The lightweight enclosure mounts in one space (1U) of a standard 19-inch rack.

Applications

Applications for the Model 5401 include broadcast facilities, college and university audio networks, arenas, stadiums, and corporate installations — virtually any application where substantial numbers of Dante-compatible devices are utilized. The Model 5401 will serve as a stable and consistent master clock for the entire Dante "network." And, as expected, the Model 5401 is compatible with all Dante devices, no matter what their primary function or manufacturer. Applications that utilize devices compatible with AES67 will also benefit from the Model 5401's resources.

Why a Dedicated Dante Master Clock?

With Dante ubiquitous in fixed and mobile facilities of all sizes and types, the need arose for a cost-effective, purpose-designed, dedicated master clock. While an inherent strength of Dante networking is its carefully implemented use of IEEE 1588 to ensure that all connected devices maintain a common timing reference, the actual performance can vary widely depending on the specific Dante devices in use and the overall number of devices on a network. There are many Dante-
compatible devices that can provide adequate basic performance as a master clock, but with the Model 5401 networked audio systems get the benefits of a high-performance "grandmaster" PTP server, along with additional unique capabilities. The unit's feature set, along with the associated internal hardware and software, was designed to provide optimum performance, flexibility, and system integrity.

Timing Sources

The Model 5401 can provide excellent master clock performance using its accurate and stable internal oscillator, which is temperature-controlled and exceeds the performance of standard Dante devices by at least an order of magnitude. While its standalone performance is excellent, the Model 5401 can also be "locked" to a variety of external signals for integration into facilities that include a master timing reference. Compatible signals include word clock, video reference, and 10 MHz.

A word clock signal is often used as a timing reference in audio-only facilities. Several word clock rates, including 48 and 96 kHz, are compatible with the Model 5401's sync input. Video reference ("sync") signals are found in most broadcast and post-production facilities. The Model 5401 supports the most-common video format/rate combinations including "black burst," bi- and tri-level HD, and several that are specifically intended for 4K applications. Industrial and commercial facilities often utilize a GPS-disciplined source of 10 MHz as a timing reference. This sine-wave signal is directly compatible with the unit's sync input.

Word Clock Output

The Model 5401 generates a precise word clock output signal that can be used as a timing reference for related equipment. It's specifically intended for "locking" audio equipment in applications that have Dante equipment whose timing reference signals are provided by a Model 5401. In this way all devices will share a common timing reference.

The word clock output rate can be selected to be 44.1, 48, 88.2, or 96 kHz. The underlying timing source for the word clock output is derived from the Model 5401's main timing source. As previously reviewed, the internal oscillator, if desired, can be "locked" to an external source. The main timing source is divided and processed by the Model 5401's logic circuitry to create the highly stable word clock output. This ensures that the word clock output is synchronized with the unit's PTP server functionality.

Audio Reference Signals

The Model 5401 generates eight sine-wave audio reference signals for general-purpose use. They are individually configurable in level and frequency. These audio "tones" are available on the Model 5401's Dante transmitter (output) channels and can be connected, using the Dante Controller application, to Dante receivers (inputs) on related equipment. The flexibility of the available routes (Dante "subscriptions") between all Dante devices on a network allows the reference signals to be used for a variety of purposes. Configuration choices allow the frequency and level of the sine-wave signals to be optimized for specific applications.

Master Clock Support for Dante Networks

A core part of the technology underlying Dante audio-over-Ethernet networking ensures that all connected devices follow a common timing reference. This is accomplished using the industry-standard IEEE 1588-2002 precision time protocol (PTP v1). Any connected Dante device can be used as a master clock; there is no requirement that a dedicated master clock device be utilized to realize adequate performance. However, the actual performance can range widely depending on the specific Dante devices available and the overall number of Dante devices on the network.

Many Dante devices utilize the 2- or 4-channel Ultimo™ integrated circuit to implement Dante connectivity. While Ultimo devices will fully support Dante audio transport they are not well suited to serve as a master clock. Ultimo's PTP performance is limited and does not have the ability to synchronize with an external timing reference. Other Dante devices use the Brooklyn II module to support Dante connectivity. In many cases these devices can provide good basic performance as a master clock including some that allow connection of an external source of word clock.

However, problems and limitations may arise when these devices are called upon to perform "double duty," serving both a primary function (such as analog-to-Dante interfacing or audio signal processing) as well as acting as a master clock. This is understandable as the main purpose of these devices is to serve a function other than as a master clock. Timing related features, such as allowing connection of a video bi- or tri-level sync signal is rarely, if ever, supported. And PTP performance can degrade when the computing power of a device is intended primarily for handling and manipulating digital audio signals. This can lead to the required PTP resources being in short supply when the number of Dante devices that need timing messages moves into the hundreds. Also, firmware updates, cabling changes, and other maintenance tasks typically associated with a general-purpose Dante audio device would impact the master clock functionality for an entire installation.

The Model 5401 was specifically designed to support a Dante-based audio system's master clock requirements. The unit's generation of audio tones and implementation of the word clock output utilize hardware that is separate from that associated with PTP functionality. As such, this secondary functionality will not interfere with PTP operation. Unlike a general-purpose audio device, once mounted in an equipment rack and the required interconnections are made, the Model 5401 will perform its tasks without risk of interruption due to conflicting resource demands.

Overall Networking Capability

Using the Dante Controller application program the Model 5401's two Gigabit Ethernet ports can be selected to operate in one of three modes: Switched, Redundant, and Pri Dante/Sec Mgmt. In the Switched mode a single Ethernet connection to either of the Model 5401's Ethernet ports will provide Dante master clock functionality as well as access to the Model 5401's management web pages. The remaining Model 5401 Ethernet port will provide network "loop-through" capability and can be used to interface with another piece of Ethernet-connected equipment. In the Redundant mode two independent Ethernet connections are made to the Model 5401's Ethernet ports, enabling Dante's redundant network capability. In this mode the Model 5401's primary Ethernet port will provide access to the management web pages. In the Pri Dante/Sec Mgmt mode, the Model 5401's primary Ethernet port will be used by the network associated with Dante while the secondary Ethernet port will be used to access the unit's management web pages. This allows separate networks to be maintained for Dante and maintenance and configuration purposes.

Operating Power

The Model 5401 allows an AC mains source of 100-240 V, 50/60 Hz to be directly connected. It can also be DC powered using a 10-18 volt source that is connected via a broadcast-standard 4-pin XLR connector. If both AC and DC power sources are connected the unit will be powered by the AC mains supply. Only if the AC mains source fails will a load be placed on the DC source. This allows a source of DC, typically an external power supply or broadcast-style battery, to serve in a backup capacity. With this arrangement normal operation can continue even if AC mains power is lost.

Future Capabilities

The Model 5401's main and logic (FPGA) embedded software (firmware) can to be updated by way of its Ethernet network connection and the internet. Multiple versions of firmware are used to support the Dante interface hardware, user management menus, and audio generation capabilities. Each can be independently updated as required.