Sound Mystery - Pulse Audio <SOLVED>

[vliscony]

Somehow or other I lost my sound, both microphone and speakers, and I have been toying with settings in Pulse AV, without success. Briefly, I got my speakers to work, but I've lost it again.

With certain operations, I hear a crackling in the speakers but that's it. Except in the regular sound control where I can test the speakers, I can get "front right" and "front left" for the Line-out built-in audio.

I am making some progress... Apparently In sound settings somehow the output channel was changed. No idea how that happened. Now the only remaining mystery is the microphones.

I am not clear on a good troubleshooting sequence. There does not appear to be anything like a reset to the defaults in Pulse AV, so I feel I have completely lost track of my changes.
Looking for a good, logical way to proceed.

[TeaSwigger]

Pulseaudio is "on top of" ALSA, usually the actual sound system. It may be useful to try alsamixer. Open a terminal, type alsamixer and press enter.

[vliscony]

Aha! This Alsamixer thingy was most helpful. I had an intuition that there was a layer beneath Pulse.
Yesterday, I stumbled upon the system sound settings and clearly there was a wrong output selected there, and it is something I never touch, so my guess is it happened somehow due to an upgrade of some sort. In any case, This Alsa thingy is most useful to figure out the rest.