Comment 47 for bug 1516025

you just replaced the headphone mic by subwoofer pin in the fixup

and add the preferred dac for your alienware

[ALC668_FIXUP_DELL_MIC_NO_PRESENCE] = {
 .type = HDA_FIXUP_PINS,
 .v.pins = (const struct hda_pintbl[]) {
  { 0x19, 0x03a1913d }, /* use as headphone mic, without its own jack detect */
   { 0x1b, 0x03a1113c }, /* use as headset mic, without its own jack detect */
   { }
 },
  .chained = true,
  .chain_id = ALC668_FIXUP_HEADSET_MODE
 },
 [ALC668_FIXUP_HEADSET_MODE] = {
 .type = HDA_FIXUP_FUNC,
 .v.func = alc_fixup_headset_mode_alc668,
 },
 };