@Xaver: No, I haven't tried ALSA without pulseaudio. I've always used both together without issue until recently.
@dibl: Thank you for the reply, but I've found the issue.
Seems that either a setting in PNMixer was changed (not by me), or the previously selected sound card now doesn't work, but selecting
default for the sound card under PNMixer preferences has resolved the issue. Or was it the recent upgrade of
libasound2 or a combination of both?

