Getting a Focusrite Scarlett Solo to work under Linux – Common Issues

The Focusrite Scarlett Solo is a pretty nifty audio interface that seems to be getting rather popular as of late. I purchased one myself to replace my dying Asus Xonar U7 that had some issues when running on Linux (and on Windows thanks to the drivers, but that’s another topic). For the most part, the Linux experience is actually fairlygood, but there are some pitfalls that you might have to look out for when running one of these with a Linux system. What follows is a list of issues that I’ve come across and how to solve them:

 

Issue: The sound card works, but cuts out when no input/output is detected. All lights are off when this happens. 

Explanation: This usually happens because of USB power saving features that are present in some tools like tlp. These deactivate USB devices automatically if they are not showing any activity.  Most distros don’t ship these by default, but some, such as Manjaro, do, even on Desktops.

Solution: If you have tlp installed on your system, you can either disable USB power saving entirely or put your Scarlett onto a blacklist so that it is never suspended. See this page for details on how to do so. If you use a different power-saving utility, check if it has a similar option or just disable it outright.

 

Issue: Microphone recordings are distorted/contain static/are unbalanced (left channel).

Explanation: This happened to me while I was using my Rode M3 condenser mic at the XLR input of the Scarlett Solo. It seems like the Scarlett reports a stereo mic input, regardless of the actual capabilities of the mic. This can cause a variety of effects, such as a 100% left channel recording, distortion or, in my case, a static noise on the right channel (might have been the 48V phantom power). This also happens on Windows.

Solution: While the solution to this problem is fairly easy under Windows (Sound settings -> change input device to mono-only), the Linux solution is a bit more complicated. As usual, there probably are multiple ways to do this, but I found that creating a remapped pulseaudio input was the most elegant solution. If you need support for ALSA, you can probably do something similar within .asoundrc.

In short, run

pacmd list-sources | grep name:

to get a list of available sources on your system. Look for the line that corresponds to your Scarlett, in my case this was:

<alsa_input.usb-Focusrite_Scarlett_Solo_USB-00.analog-stereo>

Now, open

/etc/pulse/default.pa

with your favorite text editor and add the following:

load-module module-remap-source master=alsa_input.usb-Focusrite_Scarlett_Solo_USB-00.analog-stereo source_name=Mic-Mono master_channel_map=left channel_map=mono

#Optional: Select new remap as default

set-default-source Mic-Mono

This tells pulseaudio to create a remapped microphone source that only contains the left channel of the original and is thus a mono source. Make sure to adjust the master option according to the output from pacmd and don’t forget to remove the brackets! The second line is optional and automatically sets the default source to our new redirected source.

That is all for now. If I find any other issues, i’ll update this post accordingly.

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