Comment # 11 on bug 1172017 from Takashi Iwai

Thanks!

Now I looked at the diff between the both outputs, and noticed that the speaker
DAC assignment has been changed.  Interesting, this change came from the
upstream fix for a regression on the exactly same model (T570) showing the
similar behavior.  I guess dropping this change would cure your problem.

However, since the fix is for the same model, we can't drop the stuff blindly;
it means that dropping it would result in the regression on another machine.
Possibly the problem depends on BIOS version or whatever.

So, at this moment, I created a test kernel with a patch that allows user to
specify the workaround manually.  The kernel package is being built in OBS
home:tiwai:bsc1172017 repo.  It'll appear later at
  http://download.opensuse.org/repositories/home:/tiwai:/bsc1172017/standard/

Please install the test kernel later, and create a file
/etc/modprobe.d/60-tpt570-fix.conf containing a single line:

options snd-hda-intel model=tpt470-dock-fix

... and reboot/retest.  This should change the DAC assignment and hopefully fix
your issue.  Please upload alsa-info.sh output from this after testing, no
matter whether the result is positive or not.