Linux Kernel with the ALSA Scarlett Gen 2/3 mixer driver. Use at least version 5.14 for Scarlett Gen 3 support and bug fixes for the Gen 2 support.
As of Linux 5.17, the driver is still disabled by default and needs to
be enabled at module load time with the device_setup=1 option to
insmod/modprobe. Create a file /etc/modprobe.d/scarlett.conf
containing the appropriate line for your device:
Gen 2:
- 6i6:
options snd_usb_audio vid=0x1235 pid=0x8203 device_setup=1 - 18i8:
options snd_usb_audio vid=0x1235 pid=0x8204 device_setup=1 - 18i20:
options snd_usb_audio vid=0x1235 pid=0x8201 device_setup=1
Gen 3:
- Solo:
options snd_usb_audio vid=0x1235 pid=0x8211 device_setup=1 - 2i2:
options snd_usb_audio vid=0x1235 pid=0x8210 device_setup=1 - 4i4:
options snd_usb_audio vid=0x1235 pid=0x8212 device_setup=1 - 8i6:
options snd_usb_audio vid=0x1235 pid=0x8213 device_setup=1 - 18i8:
options snd_usb_audio vid=0x1235 pid=0x8214 device_setup=1 - 18i20:
options snd_usb_audio vid=0x1235 pid=0x8215 device_setup=1
Or you can use a sledgehammer:
options snd_usb_audio device_setup=1,1,1,1
to pass that option to the first 4 USB audio devices.
To see if the driver is present and enabled: dmesg | grep -i -A 5 -B 5 scarlett should display information like:
New USB device found, idVendor=1235, idProduct=8215, bcdDevice= 6.0b
Product: Scarlett 18i20 USB
Focusrite Scarlett Gen 2/3 Mixer Driver enabled pid=0x8215
If the driver is disabled you’ll see a message like:
Focusrite Scarlett Gen 2/3 Mixer Driver disabled; use options
snd_usb_audio vid=0x1235 pid=0x8215 device_setup=1 to enable and
report any issues to [email protected]",
On Fedora, the packages alsa-lib-devel and gtk4-devel need to be
installed:
sudo dnf -y install alsa-lib-devel gtk4-devel
To build:
cd src
make -j4
To run:
./alsa-scarlett-gui
You can install it into /usr/local (binary, desktop file, and icon)
with:
sudo make install
And uninstall with:
sudo make uninstall
If no interface is detected (usually because there isn’t one connected!) you’ll see this window:
Plug in an interface or select the menu option File → Interface Simulation and load a demo file to make more interesting things happen.
If MSD Mode is enabled (as it is from the factory), you need to disable it and restart your interface to get access to its full functionality.
For the small Gen 3 interfaces (Solo and 2i2), there’s just a few buttons to control the Air, Line, Phantom Power, and Direct Monitor settings. Mostly nothing that you can’t access from the front panel anyway.
The Line/Inst (Level), Air, and 48V controls are described below in the Analogue Input Controls section.
Direct Monitor sends the analogue input signals to the analogue outputs for zero-latency monitoring. On the 2i2, you have the choice of Mono or Stereo monitoring. Mono sends both inputs to the left and right outputs. Stereo sends input 1 to the left, and input 2 to the right output.
The one control not accessible from the front panel is “Phantom Power Persistence” (menu option View → Startup) which controls the Phantom Power state when the interface is powered on.
The Gen 2 6i6+ and Gen 3 4i4+ interfaces have many controls available. The controls are split between 4 windows, 3 of which are by default hidden.
The main window has:
- Global Controls
- Analogue Input Controls
- Analogue Output Controls
The View menu option on the main window lets you open three other windows which contain the other controls:
- Routing
- Mixer
- Startup
Global controls affect the operation of the interface as a whole.
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 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.
Speaker Switching lets you swap between two pairs of monitoring speakers very easily.
When enabled (Main or Alt):
- Line Out 1–4 Volume Control Switches are locked to HW
- Line Out 3/4 routing is saved
- Line Out 3/4 routing is set to the Line Out 1/2 routing
When set to Main, Line outputs 3 and 4 are muted.
When set to Alt, Line outputs 1 and 2 are muted.
When disabled (Off):
- Global mute is activated
- Line Out 1–4 Volume Control Switches are unlocked
- Line Out 3/4 routing is restored to the saved values
Talkback lets you add another channel (usually the talkback mic) to a mix with a button push, usually to talk to musicians, and without using an additional mic channel.
The Talkback feature has a few parts:
- Talkback Microphone connected to Analogue Input 9
- Talkback Disable/Enable internal switch
- Talkback Off/On physical switch
- Talkback Mix (one switch per mix)
- Mix Input 25
To set up the talkback feature, set Mix Input 25 to the talkback source (usually Analogue Input 9), enable the Talkback Mix switches for the mixes you want the talkback input to be heard on, and change the Talkback control from Disabled to Off. Leave the Mix Input 25 gain controls at zero (−127dB), otherwise the talkback inputs will be heard even when talkback is disabled/off.
Pressing the Talkback switch on the device will then lower the volume of the other inputs on the mixes for which talkback is enabled and unmute Mix Input 25 on those mixes.
Talkback can also be activated by changing the Talkback control from Off to On.
The talkback microphone can also be used just the same as any of the other analogue inputs and routed to a physical output, PCM input, or mixer input.
This is applicable to all interfaces except the Gen 2 18i20 which has hardware-only buttons for these features.
The Level buttons are used to select between Mic/Line and Instrument level/impedance. When plugging in microphones or line-level equipment to the input, set it to “Line”. The “Inst” setting is for instrument with pickups such as guitars.
Enabling Air will transform your recordings and inspire you while making music.
Enabling Pad engages an attenuator in the channel, giving you more headroom for very hot signals.
Gen 2 devices have a hardware button for controlling phantom power.
Gen 3 devices have hardware and software control of phantom power. 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).
On Gen 3 device, phantom power is turned off by default when the interface is turned on. This can be changed in the startup configuration (menu option View → Startup).
The analogue output controls let you set the output volume (gain) on the analogue line out and headphones outputs. All interfaces support setting the gain and muting individual channels.
Click and drag up/down to change the volume, or use your mouse scroll wheel. You can also double-click on the volume dial to quickly toggle the volume between the minimum value and 0dB.
The bigger interfaces: Gen 2 18i20, Gen 3 18i8, and Gen 3 18i20 have a switchable hardware/software volume control. The position of the big volume knob on the front of the interface is indicated by the “HW” dial in the GUI. The analogue outputs can have their volume set either by the knob (“HW” setting of of the HW/SW button) or by the dials on each output (“SW” setting of the HW/SW button).
When set to HW, the mute/volume status for those channels is controlled by the hardware volume knob and the global dim/mute controls and the software volume dial and mute button for those channels are disabled.
There are “mute” and “dim” (reduce volume) buttons below the “HW” dial which affect only the outputs with “HW” control enabled. The Gen 3 18i8 doesn’t have physical buttons or indicator lights for these control, but the 18i20 devices do.
On the other (smaller) interfaces, the big volume knob on the front of the interface controls the volume of the Line 1 and 2 outputs. This is in addition to the software volume control, therefore both must be turned up in order to hear anything. The other (line 3+) analogue outputs are only controlled by the software controls.
The volume controls for the headphone outputs on each interface operate in addition to any other hardware or software volume controls for those channels. When using headphones, the volumes for those channels would usually be set to 0dB and the actual volume controlled with the physical headphone volume control(s).
The routing window allows complete control of signal routing between the hardware inputs/outputs, internal mixer, and PCM (USB) inputs/outputs.
To manage the routing connections:
-
Click and drag from a source to a destination or a destination to a source to connect them. Audio from the source will then be sent to that destination.
-
Click on a source or a destination to clear the links connected to that source/destination.
Note that a destination can only be connected to one source, but one source can be connected to many destinations. If you want a destination to receive input from more than one source, use the mixer inputs and outputs.
The Presets menu can be used to clear all connections, or to set up common configurations:
-
The “Direct” preset sets up the usual configuration using the interface as an audio interface by connecting:
- all Hardware Inputs to PCM Inputs
- all PCM Outputs to Hardware Outputs
-
The “Preamp” preset connects all Hardware Inputs to Hardware Outputs.
-
The “Stereo Out” preset connects PCM 1 and 2 Outputs to pairs of Hardware Outputs.
The Direct routing configuration is the simplest most-generally-useful configuration:
Gen 2 interfaces have as many PCM Inputs as Hardware Inputs. Gen 3 interfaces have two more PCM Inputs which the proprietary driver restricts to being “Loopback” inputs.
The “Loopback” feature advertised for Gen 3 devices is actually a limitation of the propretary Focusrite Control software. Both Gen 2 and Gen 3 devices support full reassignment of the PCM Inputs, so you can have any PCM Input as a “Loopback” or assigned to any other source.
The Gen 3 18i20 talkback microphone is Analogue Input 9 and can be routed like any other source. If you want to record using it, there is no need for the loopback hack suggested by the vendor. Just route it to a PCM Input.
If you use the Routing window to connect Sources to Mixer Inputs and Mixer Outputs to Destinations, then you can use the Mixer window to set the amount of each Mixer Input that is sent to each Mixer Output using a matrix of controls.
Click and drag up/down on the gain controls to adjust, or use your mouse scroll wheel. You can also double-click on the dial to quickly toggle between the minimum value and 0dB.
The Startup window is used to configure settings that only take effect when the interface is powered on.
When Standalone mode is enabled, the interface will continue to route audio as per the previous routing and mixer settings after it has been disconnected from a computer. By configuring the routing between the hardware and mixer inputs and outputs appropriately, the interface can act as a standalone preamp or mixer.
Standalone mode is supported on all devices supported by the kernel driver. Even the 4i4 Gen 3 (which is bus-powered) will operate in standalone mode.
When Phantom Power Persistence is enabled, the interface will restore the previous Phantom Power/48V setting when the interface is turned on. For the safety of microphones which can be damaged by phantom power, the interface defaults to having phantom power disabled when it is turned on.
When MSD Mode is enabled (as it is from the factory), the interface has reduced functionality. You’ll want to have this disabled. On the other hand, when MSD Mode is enabled, the interface presents itself as a Mass Storage Device (like a USB stick), containing a link to the Focusrite web site encouraging you to register your product and download the proprietary drivers which can’t be used on Linux.
By default, once MSD Mode is disabled, the control for it is hidden.
If for some reason you want to re-enable MSD Mode, you can set the
device_setup option to 3 to get the control back.
The entire state of the interface can be loaded and saved using the File → Load Configuration and File → Save Configuration menu options.
Internally, this uses alsactl:
- Load:
alsactl restore USB -f <fn> - Save:
alsactl store USB -f <fn>
The saved state files can be used to simulate an interface if you
don’t have one attached. The demo directory in the distribution
contains a sample file for every supported model.
The GUI can load an alsactl state file saved from a real interface
and display a GUI as if the corresponding interface was connected.
This is useful if you don’t have an interface connected and want to try, develop, or debug the GUI.
Either specify the .state filename on the command line or select the
menu option File → Interface Simulation to load.
-
The linear-dB scale of the volume controls doesn’t work well. Lower volumes (e.g. below −30dB) don’t need as much fine control as higher volumes.
-
Can’t select (focus) the gain/volume controls or use a keyboard to adjust them.
-
Level (monitoring) doesn’t work yet and is disabled (needs kernel driver update).
-
Load/Save uses
alsactlwhich will be confused if the ALSA interface name (e.g.USB) changes. -
Load/Save is not implemented for simulated interfaces.
-
Lots of “couldn't find weak ref” warnings are emitted when loading a state file for simulation.
-
The read-only status of controls in interface simulation mode does not change when the HW/SW button is clicked.
-
When there’s more than one main window open, closing one of them doesn’t free and close everything related to that card.
-
There is no facility to group channels into stereo pairs (needs kernel support to save this information in the interface).
-
There is no facility to give channels custom names (needs kernel support to save this information in the interface).
-
No keyboard accelerators (e.g. Ctrl-Q to quit) have been implemented.