Looking for a way to pipe audio from one program to another without using JACK? Pulse Audio, default sound system for Ubuntu can do this and it’s really not that hard.
1. Install pavucontrol
sudo apt install pavucontrol
2. Set up a null sink
pactl load-module module-null-sink sink_name=virtual-cable
3. Connect aps via the null sink
In this example I will use QSSTV to listen to the output of GQRX. You can use any programs you want.
Run Pulse Audio Volume Control (pavucontrol)
In the “output devices” tab, set the audio output for the program you want to monitor or record to Null Output.
In the “recording” tab, set the capture from for the “recording” program to Monitor of Null Output
And that’s about it! Enjoy!