My Xonar DX 7.1 sound card thinks that it has only 2 channels. In 12.10 I modified /etc/pulse/daemon.conf file.
http://www.webupd8.org/2009/06/enable-surround-sound-in-ubuntu-linux.html
I changed default-sample-channels = 8 but can't see no changes in Sound settings.
Does anybody had the same problem?