Applies to:
Scarlett 18i20 3rd Gen has two Optical Input ports which let you receive up to 8 channels via optical ADAT connection:
Whilst Scarlett 18i20 3rd Gen has two ports, you can't receive 16 channels over ADAT, meaning you can't connect two separate ADAT preamps (e.g. two Scarlett Octopre units), only one, unlike Scarlett 18i20 4th Gen: 16 Channel ADAT I/O - Scarlett 18i20 4th Gen
The maximum number of ADAT channels you can send to your Scarlett 18i20 3rd Gen depends on the sample rate you're using:
- Single-band (44.1/48 kHz) - 8 channels (using a single Optical In port, labelled '1-8' and '1-4')
- Dual-band (88.2/96 kHz) - 8 channels (using both Optical In ports, 4 channels for each port)
- Quad-band (176.4/192 kHz) - 0 channels (Optical In ports are disabled at quad-band sample rates)
As a universal protocol, ADAT is a one-way connection that can carry a maximum of 8 channels at 44.1/48 kHz per connection. Each time the sample rate doubles, the channel count per connection halves. Any ADAT preamp works with Scarlett 18i20 3rd Gen.
Some ADAT preamps, like Clarett+ Octopre and Scarlett Octopre Dynamic, have dual ADAT (optical) output connections - these allow you to get up to 8 channel channels at sample rates higher than 44.1/48 kHz:
Preamps with a single ADAT (optical) output allow you to get up to 8 channels using the single connection at single-band sample rates (i.e. 44.1/48 kHz). The ADAT channel count halves at higher sample rates, resulting in 4 channels at 88.2/96 kHz, and 2 channels at 176.4/192 kHz.
Note that, on Scarlett 18i20 3rd Gen, the optical inputs are disabled at quad-band sample rates (176.4/192 kHz).
For information on configuring the Digital I/O Modes of your Scarlett 18i20 3rd Gen, please see this article: Digital I/O Modes
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