Problem
After suspend PulseAudio automatically switch audio signal from other than analog output (eg. opical / S/PDIF / TOSLINK / IEC958) to HDMI output.
Solution
Edit /etc/pulse/default.pa
to comment out (add # to the start of) the line:
#load-module module-switch-on-port-available
"Reload" PulseAudio:
/usr/bin/pasuspender /bin/true
If above command not found or reload can't be completed try restart PulseAudio daemon:
pulseaudio --kill; pulseaudio --start