OK, I contacted Audiotrak. The PCI controller is custom designed (as Mikko pointed out), and the CODEC is a Crystal CS4298 (http://www.alsa-project.org/alsa/ftp/datasheets/cirrus/4298.pdf).
I read through the datasheet and was rather disturbed by the number of references to "PC multimedia applications", "entertainment PC's", "modem applications", "3D stereo enhancement" ;-) At least Audiotrak got back to me within about 2 hours though! Ryan
