[ubuntu] After upgrade to 12.04 audio input madly switches between "Line In" and "Mic"

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http://ubuntuforums.org – Hi, I just upgraded this Pentium 4 Sony VAIO to 12.04. It has a Realtek ALC260 audio chipset. After the upgrade the audio output (speakers, or headphones when connected) clicks continuously - like a geiger counter but more regular. If I open the alsamixer, or pavucontrol I can see the problem is caused by the system (PulseAudio, or ALSA - I don't know) madly switching between Mic and Line In, resulting in a series of pops. Adjusting any of the volume controls has no effect on the volume/muting of the pops. I don't understand why this happens. Maybe this is input sensing gone crazy. Ca (Hardware)