6.8 KiB
ALSA Scarlett Control Panel
Scarlett Big 4th Gen Interfaces
This document describes how to use the ALSA Scarlett Control Panel with the big Scarlett 4th Gen interfaces:
- Scarlett 4th Gen 16i16, 18i16, 18i20
FCP Driver
The big 4th Gen interfaces are supported by a new “FCP” (Focusrite Control Protocol) driver introduced in Linux 6.14. If you haven’t installed fcp-support yet, you need to do that (and update the firmware) before you can use alsa-scarlett-gui.
Main Window
The main window is divided into three sections:
- Global Controls
- Analogue Input Controls
- Analogue Output Controls
The main window for the 16i16 interface is shown below. The 18i16 and 18i20 interfaces are similar, but with more controls.
Global Controls
Clock Source (interfaces with S/PDIF or ADAT inputs only)
Clock Source selects where the interface receives its digital clock from. If you aren’t using S/PDIF or ADAT inputs, set this to Internal.
Sync Status
Sync Status indicates if the interface is locked to a valid digital clock. If you aren’t using S/PDIF or ADAT inputs and the Sync Status is Unlocked, change the Clock Source to Internal.
Sample Rate
Sample Rate is informative only, and displays the current sample rate if the interface is currently in use. In ALSA, the sample rate is set by the application using the interface, which is usually a sound server such as PulseAudio, JACK, or PipeWire.
Speaker Switching
Speaker Switching lets you swap between two pairs of monitoring speakers very easily.
Analogue Input Controls
Input Select
The “Input Select” control allows you to choose which channel the hardware 48V, Inst, Air, Auto, and Safe buttons control.
Link
The “Link” control links the 48V, Inst, Air, Auto, and Safe controls together so that they control a stereo pair of channels simultaneously.
Gain
The “Gain” controls adjust the input gain for the selected channel. Click and drag up/down on the control to adjust the gain, use your mouse scroll wheel, or click the control to select it and use the arrow keys, Page Up, Page Down, Home, and End keys.
Autogain
When the “Autogain” control is enabled, the interface will listen to the input signal for ten seconds and automatically adjust the gain to get the best signal level. When autogain is not running, the most-recent autogain exit status is shown below the “Autogain” control.
Safe
“Safe” mode is a feature that automatically reduces the gain if the signal is too loud. This can be useful to prevent clipping.
Instrument
The Inst button(s) are used to select between Mic/Line and Instrument level/impedance. When plugging in microphones or line-level equipment (such as a synthesizer, external preamp, or effects processor) to the input, set it to “Line”. The “Inst” setting is for instruments with pickups such as guitars.
Air
The Scarlett 3rd Gen introduced Air mode which transformed your recordings and inspired you while making music by boosting the signal’s high-end. The 4th Gen interfaces now call that “Air Presence” and add a new mode “Air Presence+Drive” which boosts mid-range harmonics in your sound.
Phantom Power (48V)
Turning the “48V” switch on sends “Phantom Power” to the XLR microphone input. This is required for some microphones (such as condensor microphones), and damaging to some microphones (particularly vintage ribbon microphones).
Analogue Output Controls
The analogue output controls are a bit sparse. More controls are coming soon.
Volume Knobs
The volume knobs control the volume of the analogue outputs. The two channels of the stereo pairs are shown separately, but are internally linked together.
Mute and Dim
The speaker icon buttons are “mute” and “dim” (reduce volume) buttons, corresponding to the front-panel buttons on the interface (although only the 18i20 has a physical dim button).
Routing and Mixing
The routing window allows (almost) complete control of signal routing between the hardware inputs/outputs, internal mixer, and PCM (USB) inputs/outputs.
The routing and mixing capabilities of the big 4th Gen interfaces are the same in concept as the older interfaces, but the mixer inputs are fixed and not shown in the routing window as there are too many to sensibly display.
From the main window, open the Routing window with the View → Routing menu option or pressing Ctrl-R:
To manage the routing connections:
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Click and drag from a source to a sink or a sink to a source to connect them. Audio from the source will then be sent to that sink.
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Click on a source or a sink to clear the links connected to that source/sink.
Note that a sink can only be connected to one source, but one source can be connected to many sinks. If you want a sink to receive input from more than one source, connect the sinks to mixer outputs:
- Connect mixer outputs to the sinks that you want to receive the mixed audio
- Use the Mixer window to set the amount of each mixer input that is sent to each mixer output
The Presets menu can be used to clear all connections, or to set up common configurations:
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The “Direct” preset sets up the usual configuration using the interface as a regular audio interface by connecting:
- all Hardware Inputs to PCM Inputs
- all PCM Outputs to Hardware Outputs
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The “Preamp” preset connects all Hardware Inputs to Hardware Outputs.
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The “Stereo Out” preset connects PCM 1 and 2 Outputs to pairs of Hardware Outputs.
To adjust the routing:
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Click and drag from a source to a sink or a sink to a source to connect them. Audio from the source will then be sent to that sink.
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Click on a source or a sink to clear the links connected to that source/sink.
Note that a sink can only be connected to one source, but one source can be connected to many sinks.
To adjust the mixer output levels:
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Open the mixer window with the main window View → Mixer menu option, or press Ctrl-M.
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Mixer levels can be adjusted with your keyboard or mouse in the same way as the Gain Controls.
Levels
The meters show the levels seen by the interface at every routing source as well as the analogue outputs. Open this window by selecting the View → Levels menu option or pressing Ctrl-L.
Look at this in conjunction with the routing window to understand which meter corresponds to which source or sink.
Thanks for reading this far! If you appreciate the hundreds of hours of work that went into the kernel driver, the control panel, and this documentation, please consider supporting the author with a donation.