I have tried the ppa-kernel from http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.33/ and can confirm that the options snd-hda-intel model=imac91 works for my Imac 9,1 24".
I have tried the ppa-kernel from http:// kernel. ubuntu. com/~kernel- ppa/mainline/ v2.6.33/ and can confirm that the options snd-hda-intel model=imac91 works for my Imac 9,1 24".