Ok, now I have tested with Ubuntu 14.10: Pulseaudio 4.0, Linux 3.16, same problem, so because the PulseAudio version is the same between Ubuntu 14.04 and Ubuntu 14.10 it seem it's a bug in the kernel module snd-oxygen :(
It's a regression from Linux 3.13 to Linux 3.16 → 4.4....
Ok, now I have tested with Ubuntu 14.10: Pulseaudio 4.0, Linux 3.16, same problem, so because the PulseAudio version is the same between Ubuntu 14.04 and Ubuntu 14.10 it seem it's a bug in the kernel module snd-oxygen :(
It's a regression from Linux 3.13 to Linux 3.16 → 4.4....