Asus zenbook pro UX550VE: Sound either muted or very loud

I have a new Asus zenbook pro UX550VE.

I downloaded Ubuntu 17.10 with Gnome, and installed it using the default options (erasing Windows).

I face an issue with my sound: It has only 2 states: either muted, or very loud. It makes no difference if the volume line a bit above the mute level, or at max volume.

I was facing a problem with shutting down the computer too, and I had to use nvidia drivers to solve it (solution found at Compatibility for ASUS ZenBook Pro UX550VE)

But the sound issue remains, with both Xorg and nvidia drivers.

Any help truly appreciated!

EDIT: headphones work fine, only the laptop speakers behave strange.

EDIT 2: I installed ALSA mixer, and noticed that changing Master has no effect at all for the built-in speakers, but changing PCM does the job. But this does not solve the problem, since my keyboard and sound bar on top-right corner of the screen are connected with Master, not PCM.

Solution 1:

I found a solution here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1721345 (comment #8)

I edited the file /usr/share/pulseaudio/alsa-mixer/paths/analog-output.conf.common (with sudo).

I added the following lines before the [Element PCM] block:

[Element Master]
switch = mute
volume = ignore

and run in terminal:

pulseaudio -k

and that solved the problem. Both headphones and built-in speakers work fine.