Skip to main content

Digital I/O & Clocking

Digital audio devices must share a common timing reference to transfer audio correctly. When Horizon 32 is connected to other digital audio equipment, configure the system so that one device provides the master clock and the other connected devices synchronise to it.

Choosing a clock source​

Horizon Control provides the following clock-source settings:

Horizon 32 Digital I/O & Clocking, Choosing a clock source

  • Internal — uses the Horizon system's internal clock.

  • Digital 1 — synchronises Horizon to the incoming digital signal on Digital 1.

  • Digital 2 — synchronises Horizon to the incoming digital signal on Digital 2.

  • External (Word Clock) — synchronises the Horizon system to an external BNC word-clock source.

Matching sample rates​

All devices in the digital audio system should operate at the same sample rate. Horizon uses one global sample-rate setting for all connected Horizon devices, and the DAW session and any externally clocked digital equipment should use the same rate.

Horizon 32 Digital I/O & Clocking, Matching sample rates

An incorrect clock source or mismatched sample rate can cause clicks, pops, distortion or a failure to lock to the incoming digital signal.

Word clock and multiple Horizon devices​

Horizon 32 Digital I/O & Clocking, Word clock and multiple Horizon devices

Horizon 32 provides BNC word-clock input and output. When Horizon devices are daisy-chained over Thunderbolt, secondary devices are clocked from the Primary Horizon device using word clock. The Primary Horizon uses its internal clock for this Horizon-to-Horizon chain.

Only one device should act as clock master in the connected digital system.

Checking clock status​

Horizon 32 motion ui status sample rate digital inputs

The Horizon 32 front-panel Status view displays the current sample rate, the digital-input format and whether the digital inputs are successfully clocked. The digital-input format is shown as ADAT or S/PDIF.

Horizon Control also displays the current clock source and sample rate as status indicators. Double-click either indicator to open Hardware Settings.

Word clock termination​

Horizon 32 motion ui word clock termination

Horizon 32 provides switchable 75 Ω word-clock termination. Enable termination when Horizon 32 is the final or only device receiving BNC word clock in the chain.

Word Clock Termination can be changed from the Horizon 32 front-panel Settings view.

Common clocking setups​

Horizon 32 as the clock master. Use Internal as the Horizon clock source. When connected digital equipment needs a separate clock reference, use the Horizon 32 word-clock output and configure the receiving equipment to follow that clock. Keep the sample rate consistent across Horizon, the DAW session and the connected digital devices.

Horizon 32 following an optical digital source. Select Digital 1 or Digital 2 as the clock source to synchronise Horizon to the incoming digital signal on that optical bank. Make sure the source device is configured as the clock master and that both devices use the same sample rate.

Horizon 32 following an external word-clock master. Select External (Word Clock) and connect the external master to the Horizon 32 BNC word-clock input. If Horizon 32 is the final or only receiving device on that BNC run, enable 75 Ω termination.

Multiple Horizon devices. Connect the Horizon units over Thunderbolt for host audio/data and use word clock to synchronise the secondary Horizon devices from the Primary device. The Primary device provides the monitoring system and the physical word-clock reference for the Horizon-to-Horizon chain.

Digital I/O​

Horizon 32 Digital I/O & Clocking, Digital I/O

Horizon 32 provides two optical digital inputs and two optical digital outputs. The Digital Mode setting selects ADAT or S/PDIF operation for the selected Horizon device.

ADAT channel counts​

Horizon 32 provides the following ADAT channel counts for each input or output direction:

Sample rateDigital 1Digital 2Total channels per direction
48 kHz8 channels8 channels16 channels
96 kHz4 channels4 channels8 channels
192 kHz2 channels2 channels4 channels

At higher sample rates, the first channels of each digital port remain available while the later channels become unavailable. For example, at 96 kHz, channels 1–4 of each digital port remain available.

S/PDIF mode​

Horizon 32 Digital I/O & Clocking, S/PDIF mode

When S/PDIF mode is selected, digital inputs and outputs 1–2 are shown and the Routing Matrix updates to reflect the selected mode.

S/PDIF supports sample rates up to 96 kHz.

Sample rates​

Horizon supports the following sample rates:

  • 44.1 kHz

  • 48 kHz

  • 88.2 kHz

  • 96 kHz

  • 176.4 kHz

  • 192 kHz

The selected sample rate applies globally to all Horizon devices in the daisy chain.