There are two phono (RCA/cinch) sockets on the back with left/right audio. There is also an optical digital (TOSLink S/PDIF) output which carries decoded PCM from MPEG audio streams and raw Dolby Digital (AC3) from streams that broadcast that (mainly BBC HD channels).
I suspect there's a bug in the user interface. There is a setting to turn Dolby Digital on and off, but it doesn't do anything.
