Getting Line Input to work (Microphone, etc)
Changing default subdevice configuration
* Some sound devices have multiple capture subdevices (eg. hda-intel), but pulseaudio only seems to detect the parent device, and only listens to subdevice #0. ALSA may not be configured to use your preferred device as subdevice #0 by default.
Open the pulseaudio record meter (pavumeter --record)
o Talk into your chosen device while you carry out the process and watch the meter.
+ Some channels are quite noisy even with no input (especially on integrated chipsets), so we are watching for movements that correspond to our voice.
Use alsamixer -c n (where n is your sound card number, probably 0)
+ Press F4 to get to the capture console
+ Make sure the first capture channel is enabled ("CAPTUR" in red, press space to toggle), and the volume turned up.
+ Check the first input source is switched to your chosen plug (Mic, in my case)
o At this point, you should see the record meter bouncing in response to your voice.
o I found that I had to repeat this procedure each time I wanted to use the Mic, even though the settings "stuck" in the mixer, something in the soundcard wasn't initialized until it was repeated.
o This also works if you use the "Options" tab in the standard mixer app to do the same thing.