Clocking and the Dante Network
A Dante network offers several unique clocking features that differ from traditional concepts of digital audio system clocking.
For example, rather than requiring the user to select a static clock master, the Dante network dynamically elects the clock master based on a variety of considerations. This is a great advantage when devices may be added or removed from the network - if the elected clock master isn't connected, the network elects a new clock master seamlessly with no interruption to the system.
The user does have an opportunity to influence the master selection by designating one or more devices as Preferred Master in the Dante Controller application. This permits a specific device to be assigned the role of clock master while preserving the system's capacity to elect another device as master if necessary.
Also, the Dante network master is able to sync devices at all sample rates, meaning that they can be in sync and co-exist on the network. Note that device sample rates must match to route audio between them.
The Symphony I/O Dante interface offers two audio interface modes (AIM) - Dante and Dante + PTHD. Configuration of clock source & sample rate differs between the two AIMs, as described below.
The Simple Answer: Choose Dante Network Clock Source
Given the special clocking features offered by a Dante network, the simple answer to choosing a clock source, regardless of AIM, is the Dante Network clock source. See the instructions below to set the clock source in Dante and Dante + PTHD AIMs.
Carefully consider the consequences of choosing other clock sources, as this could complicate system sync and the network's ability to dynamically elect a master device. If it's necessary to clock Symphony I/O to the Internal, word clock, or digital input clock sources, it's crucial to make two settings in Dante Controller - choose Symphony as Preferred Master and check the Enable Sync to Externalbox (even when choosing Internal clock source). These settings are made in the Dante Controller > Network View > Clock Status tab.
Configure Clock Source & Sample Rate - Dante AIM
When Symphony I/O is set to Dante audio interface mode (AIM), the following displays and controls appear on the front panel OLED:
1. Clock Source - Set Symphony I/O clock source from the front panel OLED Home View. Tap the Clock Source button, choose the desired clock source in the displayed dropdown menu, then tap OK.
2. Symphony I/O Sample Rate - The rate of the Symphony I/O chassis, i.e. the Main board and I/O modules. The Symphony I/O sample rate is set in Dante Controller > Device View > Device Config tab.
- If Clock Source is set to an external source such as word clock, the external source sample rate must match the rate selected in Dante Controller.
- A flashing sample rate indicates a mismatch between these rates.
3. Ethernet Port Status Icons - These icons display the configuration and status of the Option card Ethernet connectors.
- 1 icon displayed - the Ethernet ports are configured in Switched mode - connect either port to the Dante network, then use the remaining port to daisy-chain additional devices.
- 2 icons displayed - the Ethernet ports are configured in Redundant mode - connect the Primary port (displayed on the OLED to the left) to the Primary network, connect the Secondary port to the Secondary network.
- Icon color - when the icon is blue, the port is connected to a network; when the icon is orange, the port is not connected.
- Set the Ethernet port configuration in Dante Controller > Device View > Network Config tab. Be sure to power-cycle Symphony I/O after a port configuration change.
Configure Clock Source & Sample Rate - Dante + Pro Tools HD AIM
When Symphony I/O is set to Dante + Pro Tools audio interface mode (AIM), the following displays and controls appear on the front panel OLED. Note that sample rate and clock source selection operate differently than in Dante AIM.
1. Clock Source, Loop Master - Set Symphony I/O clock source from the Pro Tools application. Unlike Dante AIM, it's not possible to set the clock source from the front panel OLED. In Pro Tools, choose Setup menu > Hardware. The diagram below shows the correspondence between Pro Tools Clock Source dropdown menu items and Symphony I/O clock sources. For example, to choose Dante Network, select the Optical [Encl] menu item.
- Clock Source, Loop - when multiple interfaces are connected Pro Tools HD, one interface is designated the Loop Master. All other units switch to Loop clock source automatically.
- If Clock Source is set to an external source such as word clock, the external source sample rate must match the Pro Tools sample rate and the Dante sample rate.
- A flashing sample rate indicates a mismatch between these rates.
2. Symphony I/O Sample Rate - The rate of the Symphony I/O chassis, i.e. the Main board and I/O modules. The Symphony I/O sample rate is set by the Pro Tools system.
- If the Pro Tools application has been launched but no session is open, the sample rate may be set in Pro Tools > Setup menu > Hardware.
- If a Pro Tools session is open, the sample rate is determined by the session and cannot be modified.
4. Pro Tools Sample Rate - The current rate of the Pro Tools system. If Symphony I/O clock source is set to an external source, the external rate and the Pro Tools system rate must be manually matched.
5. Master Status - indicates when Symphony I/O has been configured as the Pro Tools system Loop master. In a multi-Symphony I/O Pro Tools rig, one interface is configured as the Loop Master - all remaining interfaces automatically switch to Loop clock source and should remain so.