KDE Volume not matching alsa volume in ALC294 (Asus Zenbook UM431D)

[LukasThyWalls]

Hello.

I posted some weeks ago in pulseaudio bugtracker https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/1249 about an issue, but i was thinking it should be better have here the issue too because maybe is related with other components in (K)Ubuntu system.

I will go to a copy paste, because it self explanatory:

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* Context:

OS: KUbuntu 21.04 with kernel 5.14.0rc4 mainline.
Laptop: Asus Zenbook UMD431D with ALC294
pa-info: pa-info.txt (attached)

Also recently was fixed an issue with alsa about the 4 speakers volume (two of them weren't affected by it https://bugzilla.kernel.org/show_bug.cgi?id=212547) however, this doesn't seems related to that. (That's why i use 5.14.0rc4, because 5.14 are the first with the patch).

* Issue behaviour and description

The main issue can be seen in the next video: https://www.youtube.com/watch?v=eBrHi1f9bck

Summarizing, when you go up and down the KDE volume, if you compared the desired volume in the slider with alsamixer doesn't match. But the issue is when you reach below 9%, with that the Master volume in alsamixer is 0%, so there isn't any sound, and between 1%~8% it's changing the "Speaker" slider, doing nothing. It's like the "Speaker" slider is stacked below the "Master", but that doesn't make any sense in practice.

Changing the volume in the KDE volume slider is not "linear", between 50%~100% it's more or less and the volume "feels" right, but below that, the volume goes down way faster. For example, having the volume at 25%, the sound is almost noticiable unless you put you ears near the speakers, something like this should be at 10%, but at the real 10% you have a barely noticiable sound in the speakers when you have your ears directly in them.

* Expected Results

The general volume slider should match the Master Volume in alsa, and only change that slider.

Thanks!

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Offtopic: Also i found doing testing for the kernel bug noted above, that changing to some alsa model in this laptop, then appears in the volume/audio configurator a selection of output and input what can overrides the headphone plug status, and i see it very useful, especially because if i plug a headphone without microphone i can't use the laptop built-in microphone and the only thing i can do is not use headphone. But using some models (dell-headset-multi, for example) i can do that, however, it brings the issue with the volume in the back speakers. How pulseaudio can be do this? it can be done for my laptop?