Comment 52 for bug 1575078

XPS 15 9560, linux kernel 4.10.0-38-generic, Ubuntu 17.04

After trying everything in this thread (and failing) I finally got my sound back on my headphones.

1) Install:
sudo apt-get install alsa-tools-gui

2) Launch:
hdajackretask

3) Check 'Show unconnected pins'

4) Check "override" on 0x21.

5) Apply; test sound.

6) If everything all is good now, press "install boot override"

Based on:
https://askubuntu.com/questions/895397/microphone-is-not-working-on-ubuntu-16-04