1. Connect to your box with SSH or SAMBA.
2. Type the following:
cp ~/.config/asound.conf.sample/asound.conf_double-xs35gt.sample ~/.config/asound.conf
3. In XBMC, go to System > Audio and make the following configuration:
Audio output = HDMISpeaker configuration = 7.1 (or the what your receiver is capable of)Audio output device = custom
Custom audio device = plughw:1,7Passthrough output device = custom
Custom passthrough device = plughw:1,7
4. Reboot the system