I've just installed MX-16 and having problem with my sound system. In Pulse Audio Volume Control, there are 2 options in output devices : Line Out and Headphone. I have 2 output devices as well, a speaker and an amplifier (which has 3 speakers outside of my room). When I play music from VLC, I need to switch the device output to Headphone in order to make both the speaker and the amplifier works. But it often automatically switched back to Line Out that forced me to switch it back to Headphone, again and again.
I think the problem is not on my speaker or amplifier since it worked well before (I've run Debian Wheezy before this MX-16). I've tried to install Pulse Audio Preferences (paprefs) and tried to use another media player, too.
The question is : What makes the Pulse Audio automatically switches to Line Out and how to keep it on Headphone?

https://unix.stackexchange.com/quest...ones-connected

https://bbs.archlinux.org/viewtopic.php?id=215248


https://www.tablix.org/~avian/blog/a...output_device/

that is all I could find out on something about this

I don't have a definitive answer here (and never experienced this behaviour myself), but in an effort to assist I did find this old bug report while conducting a quick search. Anyway, it describes users experiencing similar behaviour, and has some potentially useful information including the use of 'hdajackretask' to disable auto-muting/switching of the headphone output. Read post #13 onwards. It might take some experimentation though.

You might find some pulseaudio logging via
or watch in a terminal on the fly with
I've read of another workaound involving removing (or commenting out) the following PA module from /etc/pulse/default.pa
but this just apparently helps with the symptoms, not the switching (if that's what is occurring). Here's one example of that...
https://bbs.archlinux.org/viewtopic.php?id=147225

Thanks for all your help, guys!

After browsed the link that you've posted, I tried this :
List all ports using pacmd list.
I found those two ports : analog-output-lineout and analog-output-headphones
I chose the later by pacmd set-sink-port 0 analog-output-headphones
Then insert that command to /etc/pulse/default.pa

I've been playing VLC for a few hours and everything is OK.