I used the following to get sound working correctly on my new envy 15:
#edit /etc/modprobe.d/alsa-base.conf and add:
Now all audio working, including the volume control nob on the side. This also fixes some responsive issues with gnome. I noticed frequent error messages to the affect "cannot set freq 44100 to ep 0x1" and a quick google search showed the solution. The downside is not being able to use usb-audio, which I don't anyhow.