JACK breaks audio. How do I fix it?

Audio was working fine until I tried to use qjackctl and qsynth to play a MIDI keyboard. I followed this answer* to setup the keyboard and it worked. But then I noticed other applications couldn't play audio (VLC, Rhythmbox, etc.). After a reboot it was fine again. And then I set up the keyboard and the problem was back. This went on for a few days and I thought I could live with it as it fixed itself on reboot. But then it didn't. I couldn't play audio, except via qsynth and the MIDI keyboard. Now not even that audio will play.

^{*Mostly. qjackctl wasn't exactly as described, but I believe I found all the mentioned controls.}

I'm not sure what I really did with qjackctl, or how to get back where I was. I tried removing (with apt-get purge) qjackctl and qsynth but that didn't help. Now I've reinstalled qjackctl and have tried changing the which driver is used by qjackctl, all to on avail.

Ideally I'd like the MIDI keyboard to work, but far more important is getting the audio back like it should be.

I've checked all volumes using alsamixer.

I believe JACK makes pulseaudio stop (see here and here, but I don't know how to stop jack and get it back to normal.

How can I make the audio work again?

Solution 1:

Stop jackd by clicking "stop" in qjackctl or running this command in a terminal:
killall jackd
then if pulseaudio was stopped, run this command:
pulseaudio
"Standard" audio should be back.
Pulseaudio and jackd can run together installing pulseaudio-module-jack

EDIT : The real solution :
- try to install "pavucontrol" (pulse audio volume control) and check in output tab that main audio device is selected.

Also check configuration tab: This was the problem: Nateowami changed profile from "Digital Output (S/PDIF)" to "Analog Stereo Output" which solved the problem.