I had been stuggling to get the sound working on mine

Sound

The Revo is a quiet box, however on installing Ubuntu it was a bit too quiet, not producing any audio at all! We need to do three things to rectify this: 1) tell Ubuntu what type of sound card is in the machine, 2) Unmute something that should not be muted, 3) make sure all audio is going out through the HDMI socket. I managed to get all of this working, but the headphone socket no longer works so I might look at some point to see if that can be rectified. In the file /etc/modprobe.d/alsa-base add this line:
options snd-hda-intel model=3stack-6ch-dig

You may have to reboot here to get Ubuntu to pick up the right sound card. Now go to Sound Preferences (SystemPreferencesSound) and under Devices make sure that “HDA Nvidia NVIDIA HDMI (ALSA)” is selected for all non-capture options and click Close. Open a terminal and enter alsamixer you should find that “Generic 10de NVIDIA MCP7A HDMI” is showing as the chip. Press the right arrow until an entry named “IEC958 1” is highlighted and make sure it is not muted. If it is press “m” to unmute it. Press Escape to leave alsamixer. If you try the sound tests under SoundPreferencesSound you should find that they now work.

We need to make sure that the system will send all audio output through the HDMI socket to the TV and not to anywhere else, like the headphone socket. This proved a but of a frustrating part to get right, but a post on the Boxee forums at http://forum.boxee.tv/showthread.php?t=8985 pointed the way. Basically we need to provide the sound subsystem (ALSA) with a set of rules to tell it what we want it to do. As the post suggested, I create a file named .asoundrc in my home directory (note the dot at the start of the file name) and populated it with the contents of the example file from http://www.mythtv.org/wiki/Configuring_Digital_Sound#Setting_up_ALSA.27s_.asoundrc.2C_Properly. Like the forum post I commented (put a hash ‘#’ symbol in front of):
#slave.pcm “dmix-analog”

Then uncommented:
slave.pcm “dmix-digital”

To make sure the sound went though the HDMI socket I found the section with the comment:
# – Comment out “device 1” above and uncomment one of the below or create a
# new “device N” line as appropriate for your sound card or

Then commented out:
#device 1

and added:
device 3

This choice of device number was deduced by running the command aplay -l and looking up the device number for the HDMI output. At this point it is probably best to reboot and make sure the new settings have been picked up. Hopefully when the machine starts up you should hear the familiar Ubuntu start up sound. Now all that is left to do is to make sure Boxee uses the sound settings. To do this, start up Boxee, go to Settings on the left hand then to System → Audio Hardware. Change the settings to read:

Audio Output: Digital
Dolby Digital (AC3) Capable Receiver: [Ticked]
DTS Capable Receiver: [Ticked]
Audio Output Device: default
Passthrough Output Device: default