PTP time synchronised clock for use with AoIP audio networks.
PTP AoIP network, provide a GPS referenced signal via AES-3id, provide a
master wordclock studio output or distribute a PPS reference frequency
to T&M equipment.
- 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 <0.01ppm.
- 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.
The AVN-GMCS is a PTPv2 grandmaster clock for use
with AoIP applications. IEEE1588-2008 PTPv2 (precision time protocol) is
used to synchronise all the nodes within a network. To achieve this one
of the nodes must become the master clock and distribute time packets
to the others. The AVN-GMCS is designed to perform this role simply and
accurately, enabling sub micro second synchronisation between all nodes.
RAVENNA (of which AES67 is a subset) allows for the distribution
of audio across a network. For this to be possible, each of the nodes
needs to be time synchronised with one another. RAVENNA uses PTP time
stamping to achieve this, which distributes the network time but also
works out the latency involved in the delivery and adjusts the time at
each node accordingly.
Unit configuration is achieved easily either with the front panel
controls or the webserver, including the setup of the PTP profiles.
The AVN-GMCS supports the Default (RAVENNA), Media (AES67) and
AES-R16-2016 (SMPTE-ST 2059-2 & AES67 compatible) profiles and has a
‘Custom’ profile page for you to define your own.
In normal operation, the unit has PTPv2 time stamping resolution
to 8nsec. It uses a combination of a GPS receiver, a PLL (phase lock
loop) and a specialist on-board clock device to create the precise, low
jitter clock signals required to drive the physical transceiver’s time
stamping circuitry, also providing holdover if the GPS signal is lost.
The specialist on board clock is available in two different types: TCXO & OXCO, which vary in both price and accuracy:
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 is 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 which 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 wordclock 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 date and time is
available even after the unit is repowered without GPS access.
The built-in webserver, 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 synchronisation 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 super capacitor 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.
The AVN-GMC has a built-in webserver for setup and configuration.
The webserver is responsive, and resizes depending on the size of your
screen, meaning that it can be used on large monitors or small handheld
devices such as smart-phones. Help information is shown on the right
hand side of the screen so it’s a good place to go to find out how the