tinypoodle
on the input screen of alsamixer I don't have " mix" control
The options are mic (rear or front) and line in
Please read the second sentence of  Reply #5
Posting amixer output is easier for me than screenshot, showing basically same content:
tc@box:~$ amixer controls|grep Source 
numid=24,iface=MIXER,name='Capture Source'
tc@box:~$ amixer cget numid=24
numid=24,iface=MIXER,name='Capture Source'
  ; type=ENUMERATED,access=rw------,values=2,items=8
  ; Item #0 'Mic'
  ; Item #1 'CD'
  ; Item #2 'Video'
  ; Item #3 'Aux'
  ; Item #4 'Line'
  ; Item #5 'Mix'
  ; Item #6 'Mix Mono'
  ; Item #7 'Phone'
  : values=5,5