Comment 7 for bug 1551385

"2014-01-29 Change the order of elements in the output select control. This will reduce the number of relay switches. Change 'put' function to call the oxygen_update_dac_routing() function. Otherwise multichannel playback does not work. Also there is a new function to apply settings, this prevents from duplicating the code. Signed-off-by: Roman Volkov <email address hidden> Signed-off-by: Clemens Ladisch <email address hidden>"

This is the cause of the problem, it seem that PulseAudio not recognize the Speaker output.
On Ubuntu 14.04 LTS PulseAudio set the output on "Speakers"
But on Ubuntu 14.10 + the output "Speakers" doesn't exist.

In alsamixer:
Ubuntu 14.04: Speakers, Headphone, Headphone FP
Ubuntu 14.10 → 16.04: Stereo Headphone, Stereo Headphone FP, Multichannel

If I manually set "Multichannel" in alsamixer, I can play sound, but PulseAudio show only "Analog headphone" (in Pavucontrol), so the output persist on "Stereo Headphone FP" and no sound is played on the speakers. (And the output Multichannel is not set by default)
Thank you,
Valentin Crône