Comment 6 for bug 462764

@opus440
According to your original amixer output, you are capturing from the
front mic jack (ext mic), not the internal mic:

Simple mixer control 'Input Source',0
  Capabilities: cenum
  Items: 'Front Mic' 'Int Mic'
  Item0: 'Front Mic'

However, your mixer controls are set incorrectly:

Simple mixer control 'Front Mic',0
  Capabilities: pvolume pswitch
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 31
  Mono:
  Front Left: Playback 17 [55%] [-9.00dB] [off]
  Front Right: Playback 17 [55%] [-9.00dB] [off]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ muted, pretty low

Simple mixer control 'Front Mic Boost',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 3
  Front Left: 1 [33%]
  Front Right: 1 [33%]
^^^^^^^^^^^^^^^^^^^^^ pretty low

So, unmute (cap) the 'Front Mic' mixer control, raise its level, and
raise the level of 'Front Mic Boost'. Please note that this is the
front mic jack, which is an external mic.