The reason for this is probably because you connect to a Liquidsoap based server and have “mono" selected. Liquidsoap expects a stereo connection for its input.harbours. You can solve this issue by selecting "stereo" in iziCast even if you have a mono audio source like a microphone connected. If you still want to broadcast in mono to save bandwidth you need to change the Liquidsoap server configuration. Wrap your Liqduidsoap input.harbour(...) into an audio_to_stereo operator like audio_to_stereo(input.harbour(...)) in your liquidsoap.cfg.