Arch Linux

aklt

Member

Registered: 2011-11-18

Posts: 22

USB Audio through KVM works for ~30 seconds and then stops

I have a USB connected Focusrite Scarlett 2i4 which has been running fine
but today after an upgrade, the problem mentioned in the title occurs: Sound
from programs or the browser works fine and then cuts off after a random interval,
on average about 30 seconds. 

I can plug out the Scarlett USB and plug it in again and then I get audio again
for about 30 seconds.

When the sound cuts off, the volume meter in pavucontrol is still moving which to me indicates
that sound is still playing.  It does not reach the speakers however.

I checked both journalctl -xe and dmesg but I cannot see a reason for the sound
failing. 

Note that sound from a guitar I have plugged into the Scarlett still works after the
sound cuts out, so the soundcard should be working ok.

Everything has been running fine since last upgrade at the start of September. I
tried downgrading the kernel, but that did not change anything.

I am running pipewire and pipewire-pulse.

A pointer in a good direction to debug this would be greatly appreciated!

Last edited by aklt (2025-09-22 22:23:39)

dimtpap

Member

Registered: 2025-09-22

Posts: 10

Re: USB Audio through KVM works for ~30 seconds and then stops

It may be https://bbs.archlinux.org/viewtopic.php?id=308252
Try downgrading systemd to 257.9

Last edited by dimtpap (2025-09-22 20:17:56)

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

Thanks, that could definitely be related. 

I just noticed that this is in the output of journalctl -f:

Sep 22 22:26:06 nbox systemd[1]: systemd-hostnamed.service: Deactivated successfully.
Sep 22 22:26:48 nbox systemd[1]: Starting Hostname Service...
Sep 22 22:26:48 nbox systemd[1]: Started Hostname Service.

at least sometimes when the audio cuts out.  I will try to downgrade systemd.

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

Just tried downgrading systemd to 257.9 but the problem persists.

dimtpap

Member

Registered: 2025-09-22

Posts: 10

Re: USB Audio through KVM works for ~30 seconds and then stops

All systemd packages and rebooted?

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

Yes I downgraded to these:

 lib32-systemd-257.9-1-x86_64.pkg.tar.zst
 systemd-257.9-1-x86_64.pkg.tar.zst
 systemd-libs-257.9-1-x86_64.pkg.tar.zst
 systemd-sysvcompat-257.9-1-x86_64.pkg.tar.zst

I suspect it may be some power saving issue, will try to dig deeper.

Last edited by aklt (2025-09-22 21:02:54)

dimtpap

Member

Registered: 2025-09-22

Posts: 10

Re: USB Audio through KVM works for ~30 seconds and then stops

Maybe this reply can be of help https://bbs.archlinux.org/viewtopic.php … 2#p2262922

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

Thanks for the link, that does look interesting.

However I tried and I run into the same problem, although the time before the
audio cuts off is now down to about 2 seconds after I plug the Scarlett out and in again.

I added this to /etc/udev/rules.d/50-usb_power_save.rules:

# blacklist for usb autosuspend
ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="1235", ATTR{idProduct}=="8200", GOTO="power_usb_rules_end"

ACTION=="add", SUBSYSTEM=="usb", TEST=="power/control", ATTR{power/control}="auto"
LABEL="power_usb_rules_end"

after checking that the output of lsusb -v contains:

  idVendor           0x1235 Focusrite-Novation
  idProduct          0x8200 Scarlett 2i4 USB

So I am fairly certain I did not accidentally add powersaving to the card even though the
shorter time until the sound cuts off could indicate so.

Last edited by aklt (2025-09-22 21:49:16)

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

i have a StarTech 4 PC KVM switch and I noticed that if I do not plug the
Scarlett into that, the problem goes away!

Then I thought I could mitigate a KVM power save issue with similar udev
rules as mentioned above, but I am not sure which device is the KVM in the
output of lsusb, if any of them and my guesses at the device ids
have not resulted in a different behaviour.

Last edited by aklt (2025-09-22 22:08:25)

aklt

Member

Registered: 2011-11-18

Posts: 22

Re: USB Audio through KVM works for ~30 seconds and then stops

Updated the title to be more precise and am hoping to find out why this behavior changed.

seth

Member

From: Don't DM me only for attention

Registered: 2012-09-03

Posts: 71,586

Re: USB Audio through KVM works for ~30 seconds and then stops

i have a StarTech 4 PC KVM switch and I noticed that if I do not plug the
Scarlett into that, the problem goes away!

Then I thought I could mitigate a KVM power save issue with similar udev
rules as mentioned above, but I am not sure which device is the KVM in the
output of lsusb, if any of them and my guesses at the device ids
have not resulted in a different behaviour.

udevadm monitor

and plug the KVM.

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