Applies to 18i20 4th Generation in Dual ADAT mode at 44.1kHz and 48kHz sample rates.
As of Focusrite Control 2 version 1.490, Scarlett 18i20 4th Generation now features 16 channels of ADAT I/O. This means you can now combine three 18i20 4th Gens for a total of 24 analogue inputs and 26 analogue outputs.
If you want to connect two different expansion preamps or audio interfaces to your 18i20 4th Gen, take a look at this article: 16 Channel ADAT I/O - Scarlett 18i20 4th Gen.
What you'll need:
- 3 × Scarlett 18i20 4th Gens
- Focusrite Control 2 version 1.490 or later
- 4 × ADAT lightpipe/TOSLINK optical cables
-
A computer compatible with Focusrite Control 2
See Focusrite Control 2 | Release Notes -
44.1 or 48kHz sample rate
Sample Rate, Bit Depth & Buffer Size Explained -
Dual ADAT digital port mode
RCA S/PDIF input will be disabled — Digital I/O Modes
ADAT is the digital audio format that we'll use to connect the three 18i20s, as only one 18i20 can be connected via USB to your computer at once. For the purposes of this guide, we'll refer to the 18i20 that will act as your main audio interface, connected to the computer via USB, as the host. The other two units will be referred to as expansions.
Step 1: Configure the expansion 18i20s
As Focusrite Control 2 can only work with one 18i20 via USB, you'll need to connect the expansion 18i20s one at a time to configure them as standalone expansion preamps.
Now, click this button and follow the instructions to set up your expansion 18i20s in Standalone Mode.
Then, you can set the routing, sample rate, and clocking as shown below.
Expansion 18i20s: 
Routing
Unless you have another setup in mind, use the standard standalone routing for both expansion 18i20s:
- Under Analogue outputs, set the Source for Outputs 1–8 to ADAT 1–8.
- Under Digital outputs, set the Source for ADAT 1–8 to Analogue 1–8.
Expansion 18i20s: 
Sample rate & clocking
The full 16 channels of ADAT I/O are only available at 44.1 and 48kHz. You need to set your expansion 18i20s to the same sample rate that your host 18i20 and DAW will use.
- Go to
More options →
Preferences →
- Select your chosen Sample rate, 44.1 or 48kHz, for both expansion 18i20s.
If you need to change sample rate in future, repeat this process for both expansion units.
Clocking will enable your audio devices to digitally synchronise with one another. For this setup, both of your expansion 18i20s will follow the digital clock from the leader, your host 18i20, via ADAT Optical In 1.
- Set the Clock source to ADAT Port 1 for both expansion 18i20s.
If you'd like to know more about selecting clock sources, check out this article: Understanding Clocking.
As you haven't connected any ADAT cables to the expansion 18i20s yet, Focusrite Control 2 will say Not synced ⚫︎. Lastly, you can leave the Digital port mode as-is on the expansion units, since you aren't going to be using Optical 2 or S/PDIF on the expansion 18i20s.
To learn more about selecting Digital port modes, see this article: Digital I/O Modes.
You can now disconnect the USB first expansion 18i20 from the computer and repeat the steps above for the second unit.
Step 2: ADAT connections
Using four ADAT lightpipe/TOSLINK cables, connect your three 18i20s as shown in the diagram below.
Expansion 1 Optical Out 1 to Host Optical In 1
Expansion 1 Optical In 1 to Host Optical Out 1
Expansion 2 Optical Out 1 to Host Optical In 2
Expansion 2 Optical In 1 to Host Optical Out 2
Step 3: Configure the host 18i20
Now you can connect the host 18i20 to the computer via USB. As with the expansion units, accept any firmware updates, and we recommend that you restore the 18i20 to default settings unless there are any settings you want to preserve.
More options →
Preferences →
Device settings → Reset to default settings
Host 18i20: Routing
As before, unless you have another setup that you want to use, configure the ADAT outputs like this:
- Under Digital outputs, set the Source for ADAT 1–16 to Playback 11–26.
Now, select the same sample rate as you chose for the expansion 18i20s. Remember, you must use a sample rate of either 44.1 or 48kHz to enable the full 16-channels of ADAT I/O, and your 18i20s and your DAW must all use the same sample rate.
- Go to
- Select your chosen Sample rate, 44.1 or 48kHz, for the host 18i20*.
*Your host 18i20 may automatically switch to use the sample rate of your DAW. Ensure any software is also operating at your chosen sample rate of either 44.1kHz or 48kHz.
Your host 18i20 will be the clock leader, so you need to configure it to follow its own internal clock.
- Set the host 18i20's Clock source to Internal.
If you'd like to know more about selecting clock sources, check out this article: Understanding Clocking.
Finally, as you are using both sets of ADAT optical ports on the host 18i20, you'll need to put the host 18i20 into Dual ADAT mode (Understanding Clocking).
- Set the host 18i20's Dual port mode to Dual ADAT.
To learn more about selecting Digital port modes, see this article: Digital I/O Modes.
Now you have configured the sample rate and clocking for all three 18i20s, and you have connected the ADAT cables, all three 18i20s should be synced. You should see Synced ⚫︎ in Focusrite Control 2 for the host 18i20, and the Sync Status LED should be lit green on all three 18i20s.
Step 4: Test the ADAT inputs and outputs
You can check if a signal from the expansion 18i20s is being received by the host 18i20 in the Inputs section of Focusrite Control 2. Inputs 13–28 will show signals received from ADAT 1–16.
You can also test the inputs and outputs in your DAW. If you have used the routing we suggested, the inputs and outputs of your three 18i20s will occupy the following input and output numbers in your DAW.
Input numbers
| DAW | Hardware Input |
|---|---|
| 1 | Host Analogue 1 |
| 2 | Host Analogue 2 |
| 3 | Host Analogue 3 |
| 4 | Host Analogue 4 |
| 5 | Host Analogue 5 |
| 6 | Host Analogue 6 |
| 7 | Host Analogue 7 |
| 8 | Host Analogue 8 |
| 9 / Loop 1 | Host Loopback 1 |
| 10 / Loop 2 | Host Loopback 2 |
| 11 / Digital 1 | Exp. 1 Analogue 1 |
| 12 / Digital 2 | Exp. 1 Analogue 2 |
| 13 / Digital 3 | Exp. 1 Analogue 3 |
| 14 / Digital 4 | Exp. 1 Analogue 4 |
| 15 / Digital 5 | Exp. 1 Analogue 5 |
| 16 / Digital 6 | Exp. 1 Analogue 6 |
| 17 / Digital 7 | Exp. 1 Analogue 7 |
| 18 / Digital 8 | Exp. 1 Analogue 8 |
| 19 / Digital 9 | Exp. 2 Analogue 1 |
| 20 / Digital 10 | Exp. 2 Analogue 2 |
| 21 / Digital 11 | Exp. 2 Analogue 3 |
| 22 / Digital 12 | Exp. 2 Analogue 4 |
| 23 / Digital 13 | Exp. 2 Analogue 5 |
| 24 / Digital 14 | Exp. 2 Analogue 6 |
| 25 / Digital 15 | Exp. 2 Analogue 7 |
| 26 / Digital 16 | Exp. 2 Analogue 8 |
Output numbers
| DAW | Focusrite Control 2 | Hardware Output |
|---|---|---|
| 1–2 | Playback 1 - 2 | Depends on Mix A settings |
| 3–4 | Playback 3 - 4 | Host Output 3 - 4 |
| 5–6 | Playback 5 - 6 | Host Output 5 - 6 |
| 7–8 | Playback 7 - 8 | Host Output 7 - 8 |
| 9–10 | Playback 9 - 10 | Host Output 9 - 10 |
| 11–12 | Playback 11 - 12 | Exp. 1 Output 1 - 2 |
| 13–14 | Playback 13 - 14 | Exp. 1 Output 3 - 4 |
| 15–16 | Playback 15 - 16 | Exp. 1 Output 5 - 6 |
| 17–18 | Playback 17 - 18 | Exp. 1 Output 7 - 8 |
| 19–20 | Playback 19 - 20 | Exp. 2 Output 1 - 2 |
| 21–22 | Playback 21 - 22 | Exp. 2 Output 3 - 4 |
| 23–24 | Playback 23 - 24 | Exp. 2 Output 5 - 6 |
| 25–26 | Playback 25 - 26 | Exp. 2 Output 7 - 8 |
As well as testing the outputs in your DAW, you can see if a signal is being routed to an output successfully by checking the Routing section of Focusrite Control 2.
Lastly, you can use the front panel meters to check the signals for the analogue inputs and outputs on each 18i20. Meters L and R always display the metering for analogue Outputs 1 - 2. By default, meters 1 to 8 display metering for analogue inputs 1 to 8. However, if you press the Output button, meters 1 to 8 will display metering for analogue Outputs 3 to 10.
You should now be set up and ready to use your three 18i20s.
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