I have installed pulseaudio and pavucontrol on Xfce (debian GNU Linux amd64 jessie 8 stable; GA-X79-UD3 with two GPUs). I managed in /etc/pulse/default.pa to switch from default HDMI to analog output:
### Make some devices default
# set-default-source alsa_input.pci-0000_00_1b.analog-stereo
However, with the for-last line commented out, as above, or uncommented out, <pavucontrol> command leads to a blinking device, i.e., (as far as I understand) there is a continuous switch between headphone and line out analog. I noticed on Internet that this is a bug.
With the same OS on a simpler desktop without GPUs/CUDA (and gnome3 in place of Xfce) there is no such problem, and sound works nicely on the same couple of speakers.
hi, you could try to replace those pulseaudio functions with ALSA. I had, and still I have it , a problem with Pulseaudio in KDE Plasma, and could temporally solve it with kmix (ALSA for KDE).