Pipe/Mix Line In to Output in PulseAudio

1. Load the loopback module

pacmd load-module module-loopback latency_msec=5

creates a playback and a recording device.

2. Configure the devices in pavucontrol

In pavucontrol, in the Recording tab, set the "Loopback" device's from input device to the device which receives the line in signal.

recording settings

In the Playback tab, set the "Loopback" device's on output device to the device through which you want to hear the line in signal.

playback settings

3. Troubleshooting

If the audio signal has issues, remove the module with pacmd unload-module module-loopback and retry a higher latency_msec= value

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