Many xruns on MOD Desktop Linux Edition with Scarlett Solo Gen4

Using MOD devices Setup Questions
#1

Hi

I own MOD Dwarf but recently I have used MOD Desktop a lot.

Today I received a newly purchased Forcusrite Scarlett Solo Gen4 and I connected it to my Ubuntu 24.04.1 LTS.

I could set Scarlett Solo Gen4 up by installing alsa-scarlett-gui_0.4.0_amd64.deb and scarlett2-firmware_2128b.deb.
I can hear music and guitar sounds with the Direct button without noise.

But after starting MOD Desktop there are a lot of xruns and noise.

alsa-scarlett-gui has a lot of options like routing, mixing, and so on.
So maybe I wrongly misconfigured the Scarlet Solo Gen4 because I still don’t know each option well.

So if there’s someone who made MOD Desktop work well with Scarlett Solo Gen4 on Linux, please share the configurations.

#2

Maybe start by sharing your current configuration?

Which blocksize and samplerate are you using with the device?

#3

Thank you for your suggestion.
I reviewed my alsa-scarlett-gui and pedalboard and I found my pedalboard is too heavy.

Now CPU load is low though but xruns are too many.

Screenshot from 2024-12-11 22-09-31
Screenshot from 2024-12-11 22-09-311920Ă—1080 199 KB

#4

It’s not possible to set a specific blocksize?

#5

No blocksize configuration available on the alsa-scarlett-gui.

#6

You can set the buffer size via jack. Try qtjackctl

#7

I can set the buffer size, but can’t start jackd with qjackctl because MOD Desktop has its own jackd instance.

#8

With usb devices and alsa driver you’ll probably want 3 periods.

You can totally pre-start your system jack instance and have mod audio connect to it-

for example with full preempting,
jackd -Rv -d alsa -p256 -n3 -i2 -02

Then launch mod desktop with jack, you should see the jack session splurt some helpful logs of this connection as its made.

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#9

edit- fix typo and without the full preemting assumption, jackd -d alsa -p256 -n3 -i2 -o2

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#10

I tried the command jackd -d alsa -p256 -n3 -i2 -o2 from the terminal, but couldn’t get a good result. Still a lot of noise and xruns.

I checked the jackd+host logging and found no difference between the command execution and none-execution.

#11

You need to tune your linux installation for low latency audio.
You need to enable Real Time audio and set it properly.
Important part for sure is the CPU governor, set it to “performance”. Also you didn’t specify what CPU/system you are running… it’s not an audio card problem probably.

Start with this: Professional audio - ArchWiki

#12

Thanks for your information.

I stopped using Ubuntu for MOD Desktop because the Pro subscription is needed to enabling Real-Time Ubuntu.
If I stick with Ubuntu, I would try Ubuntu Studio.

But with Manjaro with/without rt-kernel, almost all xruns were gone with the command below.

$ sudo cpupower frequency-set -g performance

My inxi output is the following.

$ inxi
CPU: quad core Intel Core i7-8650U (-MT MCP-) speed/min/max: 3912/400/4200 MHz
Kernel: 6.12.4-1-MANJARO x86_64 Up: 4m Mem: 2.16/15.37 GiB (14.0%)
Storage: 953.88 GiB (0.9% used) Procs: 259 Shell: Bash inxi: 3.3.36
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#13

With Ubuntu Studio 24.04.1 LTS, there are almost no xruns with the system default.

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#14

As I said, the performance governor does to most… I’ve experienced the same.
Also, keep in mind that you are using a pretty old CPU, considering the capabilities of the recent plugins today, such as NAM, AIDA and so on… it might not have all the power to run all the things you want smoothly. You need to check for single core performances. Also, keep in mind that what causes xruns it’s the RealTime CPU usage, not the CPU usage in general. You need to check what JACK/Mod Desktop is saying. If you see “DSP usage” around 50% (which is Real Time Usage) it’s time to stop adding plugins to your pedalboard :slight_smile:

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