I did a clean install of Ubuntu 11.04 and everything went fine.
The sound was working without a problem with the on-board device Azalia (Intel HDA) from the ASUS Crosshair IV Formula motherboard.
Then, i installed the proprietary drivers for the AMD Radeon HD 6870 through this guide.
Now the sound is gone.
If i go to Sound Preferences, on the Output options i see two devices for sound output:
- Internal Audio Analog Stereo (selected)
- Barts HDMI Audio [Radeon HD 6800 Series]
Is there anything i can do?
If you need any more information, let me know.