I saw a post here from an M520 owner that suggests an inverted amp setting: http://www.ubuntux.org/centrino-sound-problem
Run alsamixer with this command: alsamixer
Turn off the 'External Amp' setting. and see if you get sound.
I saw a post here from an M520 owner that suggests an inverted amp setting: http:// www.ubuntux. org/centrino- sound-problem
Run alsamixer with this command:
alsamixer
Turn off the 'External Amp' setting. and see if you get sound.