Comment 14 for bug 1442428

1) I disconnected my speakers from the rear jack, and plugged my headphones into the front jack. After rebooting, the headphones are detected and the sound works - everything is perfect. I opened the Sound Settings dialog, and "Headphones" are present, "Line Out" is absent.

2) I plugged my speakers into the rear jack, and sound immediately stopped playing from the headphones. But the speakers are also silent, even though they're not muted in the GUI. I try muting and unmuting, switching between headphones and line out in the GUI, but nothing works - neither the speakers, nor the headphones.

these are pulseaudio bug since you don't have the above patch,

line out jacks are muted by the driver
headphone are muted by pulseaudio