I recall there was a thread some time ago about getting the above soundcard to work well on netbooks/laptops. I dealt with it by monkeying around and trying to see which settings worked in alsamixer until I got it to work. This included doing non-intuitive things like muting the front speaker (which muted the front speaker) but left the headphones working.
So, I got tired of it and went to http://www.alsa-project.org/snapshot/
and downloaded the online snapshot for alsa-driver. I unzipped it and installed it with ./configure, make and then root make install.
Now, I get a new looking gnome alsa-mixer under the Soundcard Utilities that actually includes a headphone slider. And, a great big AND, when I plug in the headphones it automatically mutes the front speaker and routes to the headphones. I have tested it with Jack and LinuxSampler. What a relief. Just thought I would share.
Please note this also worked on ArchBang on another partition on my Netbook.
As always though Your Mileage May Vary.
The audio system seems snappier too (important on such an underpowered machine).