I found an earlier 'solved' post in this forum (linked below) that didn't give a satisfying solution to the problem of remapping a stereo output to become a mono output. I found another seemingly better solution, making use of only pulseaudio, and only requiring a one-time change of a config-file (at least concerning your main internal soundcard).

Original thread: http://ubuntuforums.org/showthread.php?t=1049371
Answer based on https://wiki.archlinux.org/index.php...stereo_to_mono

Solution:

For every soundcard you want to enable a mono option for - get the pulseaudio registered name of it. This can be done by writing the following in your shell:
Code:
pacmd list-sinks | grep name:
Next, for all the soundcards chosen, add the following line to your "/etc/pulse/default.pa" (e.g. use gedit or nano), where you replace the word 'foo' with the soundcards name (seen inside angle-brackets in the previous output):
Code:
load-module module-remap-sink master=foo sink_name=mono channels=2 channel_map=mono,mono
The reason for separating these two steps instead of having them in a single command, is to be able to choose the relevant soundcards to enable remapping for. There will emerge one more audio-output per soundcard in your sound-settings (e.g. pavucontrol), and you possibly don't wan't this for all your soundcards.
Another reason for one not to want this, is if some of the soundcards are external - then they won't neccesarily be connected to the computer all the time; where the pulseaudio server will fail to start.

Other answers, avoiding this last problem are very wellcome..