Sonifex AVN-GMCS PTP Grandmaster Clock, GPS, IP, TXCO, Rackmount

Sonifex AVN-GMCS PTP Grandmaster Clock, GPS, IP, TXCO, Rackmount

A PTPv2 grandmaster clock for use with AoIP applications is called the AVN-GMCS. PTPv2, or precision time protocol, is defined in IEEE1588-2008 and is used to synchronize all nodes in a network. To accomplish this, one node needs to take on the role of master clock and send time packets to the other nodes. This task can be completed by the AVN-GMCS with ease and accuracy, allowing for sub-microsecond synchronization between every node. Audio can be distributed across a network using RAVENNA, of which AES67 is a subset. Every node must be in time sync with every other node for this to be feasible. To do this, RAVENNA makes use of PTP time stamping, which not only divides up the network time but also calculates the delivery latency and modifies the time at each node by it. Unit configuration, including PTP profile setup, can be accomplished with ease via the website or front panel controls.

The AVN-GMCS features a 'Custom' profile page where you can define your own in addition to supporting the Default (RAVENNA), Media (AES67), and AES-R16-2016 (SMPTE-ST 2059-2 & AES67 compatible) profiles. The device has an 8nsec PTPv2 time stamping resolution when operating normally. The exact, low-jitter clock signals needed to power the physical transceiver's time-stamping circuitry are produced by combining a GPS receiver, a PLL (phase lock loop), and a specialized onboard clock device. This allows for a holdover if the GPS signal is lost.

The expert on-board clock comes in two varieties, TCXO & OXCO, which differ in terms of accuracy and cost:

AVN-GMCS – TCXO Temperature Compensated Oscillator accurate to 1 part per million (worst case 1 sec gain/loss every 11.5 days). *
AVN-GMCOS – OCXO Oven Controlled Oscillator accurate to 0.1 parts per million (worst case 1 sec gain/loss every 115 days). *

GPS presence and the number of satellites received are shown on the front panel, together with status information on output sample rates, sync type, and profile type. The unit also has a screen-saver option that shows the current time.

Although designed as a grandmaster clock, a separate clock input can act as an alternative reference source to GPS which the unit can ‘slave’ to. Clock outputs, driven from the physical transceiver, can be used to provide media clocks for external equipment local to the AVN-GMC when it is in both ‘master’ and ‘slave’ states. The clock outputs are available as a single AES-3id output and two outputs which can be selected as either word clock or variable PPS. The word clock can operate at 32, 44.1, 48, 96, 176.4 and 192kHz. When set as a variable PPS output, the unit can act as a clock master to distribute a reference frequency to test and measurement equipment.

The unit shows UTC as standard, but can be set to show ‘local time’ on the front panel, by adding a time offset. Daylight saving time changes can be accommodated by entering Spring Forward and Fall Back dates. It has a real-time clock so that accurate data and time is available even after the unit is repowered without GPS access.

The built-in web server, or front panel OLED display, can be used to configure the unit. The webserver is a responsive design meaning that it can be used with small screens on smartphones and tablets.

Front panel LEDs show the synchronization status, GPS lock, and the status of the AC and DC power supply inputs.

The brightness of the OLED display and LED indicators can be adjusted for low or high-lighting conditions 4 general-purpose outputs indicate critical states for the unit using a 9-way D-type connector mounted on the rear panel. Pull down when active pins are supplied for GPS lock status, external sync present, AC power present, and DC power present.

The unit has a front panel power button and dual power connectors - an IEC mains input and a 12V DC input, which allows the AVN-GMCS to be used for both studio and mobile installations. Moreover, this allows for a secondary power source to reduce the effect of power-down events. In any case, the unit monitors the status of both power sources and displays this on the front panel.

The unit can be put into a low-power sleep mode when not in use, with an instant start when power is re-applied. In power-off situations, a supercapacitor is used to keep the GPS receiver powered in a low power mode for more than 20 hours, enabling the receiver to regain lock immediately rather than having to ‘cold’ start.

Key Features

• AES67/RAVENNA/AES-R16 compatible.
• GPS satellites received indicator.
• Master and slave sync modes.
• 8ns PTPv2 time stamping resolution.
• Holdover drift <1ppm, with an option for <0.1ppm.
• AES-3id, wordclock & variable PPS outputs.
• Analogue master input.
• Dual power supply inputs.
• Front panel display.
• GPS sync and power supply present LED indicators.
• Real time clock for accurate date/time.
• Responsive design Ethernet webserver and front panel control & configuration.