I was having problems with sound (mono only output), so following advice from another askubuntu question I made some edits in /etc/pulse/default.pa.

After rebooting I had no sound at all. So I deleted /etc/pulse/default.pa entirely and tried another reboot. I did not backup the file (stupid, I know).

How to come back to working config?

I tried: sudo apt-get remove pulseaudio, reboot, sudo apt-get install pulseaudio and reboot.

It's still not working. The file /etc/pulse/default.pa is missing.

Here's what pulseaudio and pacmd commands show:

$ pulseaudio 

E: [pulseaudio] main.c: Daemon startup without any loaded modules, refusing to work.

$ pacmd

No PulseAudio daemon running, or not running as session daemon.