I'm using an Ultra 1 to play audio, with audioplay.
   
   It works, but the problem is, it plays it both to the back-panel jack
   and to the internal speaker(s?).  I want to shut off the latter, so the
   machine itself is quiet and the sound comes entirely from the external
   sound system.


this should be a matter of fixing the cs4231 driver to properly report
what it does and does not support to the higher level audio / mixer
drivers.  currently, it does it wrong, i don't know how or why, but
i know it's wrong :-)  i don't know audio(9) very well...


.mrg.