Comment 22 for bug 1365769

seem you are not using latest alsa driver

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/hda?id=f1e762ddc8035f803d15f8c524151bf788482ec2

Simple mixer control 'Input Source',0
  Capabilities: cenum
  Items: 'Front Mic' 'Rear Mic' 'Line'
  Item0: 'Rear Mic'
Simple mixer control 'Input Source',1
  Capabilities: cenum
  Items: 'Front Mic' 'Rear Mic' 'Line'
  Item0: 'Rear Mic'
Simple mixer control 'Loopback Mixing',0
  Capabilities: enum
  Items: 'Disabled' 'Enabled'
  Item0: 'Disabled'

Node 0x1e [Audio Selector] wcaps 0x300501: Stereo
  Power states: D0 D1 D2 D3
  Power: setting=D0, actual=D0
  Connection: 6
     0x2c 0x2b* 0x2a 0x29 0x28 0x21

most via codecs able to record the playing signal by select stereo mix ( node 0x21)

Node 0x21 [Audio Mixer] wcaps 0x20050b: Stereo Amp-In
  Control: name="Front Mic Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=3, ofs=0
  Control: name="Front Mic Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=3, ofs=0
  Control: name="Rear Mic Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=1, ofs=0
  Control: name="Rear Mic Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=1, ofs=0
  Control: name="Line Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=2, ofs=0
  Control: name="Line Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=2, ofs=0
  Amp-In caps: ofs=0x17, nsteps=0x1f, stepsize=0x05, mute=1
  Amp-In vals: [0x80 0x80] [0x1f 0x1f] [0x81 0x81] [0x80 0x80] [0x80 0x80]
  Power states: D0 D1 D2 D3
  Power: setting=D0, actual=D0
  Connection: 5
     0x2c 0x2b 0x2a 0x29 0x28
  In-driver Connection: 6
     0x2c 0x2b 0x2a 0x29 0x28 0x08

node 0x08 is the audio output