Further information in case it helps!
"etc/asound.state" seems to have a section at the end headed 'state.HD'. Only two controls are showm. Control.1 ends with :-
name 'Mic Capture Switch'
This is if the capture is enabled, value goes to false when capture is not enabled.
Control.2 is the gain setting for the mic.
When machine reboots the setting for mic capture is reset to false from somewhere. Any ideas where?