If you're looking to capture the output of your soundcard, you'll have to use pulsesrc and set the device property to your soundcard's analog-stereo monitor source. Have a look here.
Here the relevant source would be alsa_output.pci-0000_80_01.0.analog-stereo.monitor
and you'd change your pipeline's input to
pulsesrc device = "alsa_output.pci-0000_80_01.0.analog-stereo.monitor"