Comment 56 for bug 1321421

Running Ubuntu 14.10 with an Asus Z97-C motherboard, 3.16.0-30-generic kernel.

Adding

options snd-hda-intel vid=8086 pid=8ca0 snoop=0

to alsa-base.conf does solve the problem, but only partially in my opinion.

The thing is the sound is far from perfect. I can hear the sound "scratching" from time to time.

When watching alsamixer, i have noticed that when the sound is scratching, the level of the PCM column if changing rapidly. It decreases and then goes back to the original value.

I thought it was an issue related to auto mute, but this feature is disabled in alsamixer.