Librem15 headphone audio has echo and bad stereo image

I recently got an HDMI monitor and tried switching to use HDMI as audio output. That worked pretty well via gnome-control–center but I noticed that some audio had a bad stereo image like one channel was delayed or with hall reverb or something odd. I started messing around with settings in alsamixer and reverting back to built-in audio in gnome-control-center.

At this point sound through the laptop speakers sounds fine but headphone output either built-in audio or via HDMI has the strange behavior.

Any ideas? Maybe I messed something up in alsamixer.

That’s a pretty weird problem… the headphone output is a completely different route than the HDMI out.
The headphone goes through the digital audio output to the codec chip and is then routed to the analog audio output. The HDMI audio in contrast is a function of the graphics logic and goes pretty straight in digital format out of the HDMI port.

Since these are two completely different audio paths I doubt that this is a hardware or driver issue and would support your theory of a settings issue. It might be Alsa or Pulse audio. Since the Alsa mixers have little to do with the HDMI I would almost point towards Pulse.



An easy way to test the software hypothesis would be to create a second, temporary user account on your system and log into that one, since it won’t have any existing settings. You could also try with a liveUSB image if you’re familiar with that. Not sure where ALSAmixer etc. store their settings though, I know there’s ~/.config/pulse at least (that you could clear after doing “pulseaudio --kill”, then relogin)

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Looks like alsa saves state at /var/lib/alsa/asound.state.

Yes, I can experiment with a live USB image and new account as well.

I’ll try the ideas so far and see where it gets me. Thanks both of you!

Interestingly I was just viewing a video via chrome and had garbled audio in my headphones. If I used gnome-control-center, Sound and adjust the balance all left or all right the sound is fine and louder and in both headphone speakers. Odd. Haven’t had an opportunity to try any other diagnostics but figured this might be an interesting note.