I had a strange problem after installation Ardour from SVN (Ubuntu 14.04): line input not connecting to Ardour. Only a microphone and I heard loud noise immediately after the addition of audio tracks (setup ALSA: alsa mixer: https://cloud.mail.ru/public/6f02bd10da6f/alsa.png).
I opened JackCtl and clicked "disconnect all". Then I restart my computer and saw PulseAudio JACK Source:
Then I run Ardour and now line input is connected and noise disappeared.
The next start computer was successful, but PulseAudio JACK Source did not appear.
Is this normal?