Clemens Ladisch wrote:
  There should be mixer controls for this,
depending on the codec used
 by this board.  What is the output of "amixer controls"? 
 Yes, I thought so, but neither alsamixer nor kmix give me any clue.
 amixer gives me:
 ... 
Probably your codec wasn't detected correctly.  What are the contents
of /proc/asound/cards?  If it says "unknown codec", a more up-to-date
version of ALSA might help.
HTH
Clemens