Comment 7 for bug 466936

I am experiencing the same kind of distortion, if I don't select Analog Stereo Output/Duplex. Updated to Karmic a few hours ago and in Jaunty it worked all fine.

Doing speaker-test -c6 -tsine the distortion affects the two right channels and the LFE cannel most, but the others aren't completely clean. There is also some kind of regular click noise during the high-pitched distortion.
speaker-test -c6 -tsine -Dsurround51 emits clean sound (actually, front right and also rear left are still *slightly* distorted, but its the same as with Analog Stereo)

$ lspci | grep audio
00:06.0 Multimedia audio controller: Creative Labs CA0106 Soundblaster

$ aplay -l
**** Liste von PLAYBACK Geräten ****
Karte 0: CA0106 [CA0106], Gerät 0: ca0106 [CA0106]
  Untergeordnete Geräte: 1/1
  Untergeordnetes Gerät '0: subdevice #0
Karte 0: CA0106 [CA0106], Gerät 1: ca0106 [CA0106]
  Untergeordnete Geräte: 1/1
  Untergeordnetes Gerät '0: subdevice #0
Karte 0: CA0106 [CA0106], Gerät 2: ca0106 [CA0106]
  Untergeordnete Geräte: 1/1
  Untergeordnetes Gerät '0: subdevice #0
Karte 0: CA0106 [CA0106], Gerät 3: ca0106 [CA0106]
  Untergeordnete Geräte: 1/1
  Untergeordnetes Gerät '0: subdevice #0