External audio output not recognized, output through internal laptop speakers even when external output connected

[Yahel Galili]

As described in summary

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: alsa-base 1.0.25+dfsg-0ubuntu5
ProcVersionSignature: Ubuntu 4.4.0-98.121-generic 4.4.90
Uname: Linux 4.4.0-98-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: yahgalili 1851 F.... pulseaudio
CurrentDesktop: Unity
Date: Sun Nov 12 12:32:30 2017
InstallationDate: Installed on 2016-07-16 (484 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:PCH successful
Symptom_Card: Built-in Audio - HDA Intel PCH
Symptom_Jack: Black Headphone Out, Left
Symptom_PulsePlaybackTest: PulseAudio playback test successful
Symptom_Type: None of the above
Title: [Inspiron 13-7359, Conexant CX20722, Black Headphone Out, Left] Playback problem
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/20/2017
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.17.0
dmi.board.name: 0TDTV6
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.17.0:bd06/20/2017:svnDellInc.:pnInspiron13-7359:pvr:rvnDellInc.:rn0TDTV6:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: Inspiron 13-7359
dmi.sys.vendor: Dell Inc.