it was
module-sine
causing the pops and crackling. Somehow~/.config/pulse/default.pa
was set to load this module
Manjaro does not by default create configuration file ~/.config/pulse/default.pa
A user would normally create it to replace the default configuration /etc/pulse/default.pa
There are only 2 other posts on this forum that mention use of module-sine and neither mention using ~/.config/pulse/default.pa
Alsamixer automute does not work
Hearing a lot of bad noise when no audio is playing (on battery)