baseband audio is working for me, however, two things needed tweaking beforehand:
1. the name of my soundcard is "plughw:CARD=Loopback,DEV=1" which does not fit into the naming scheme of wsprdaemon
2. the recorded audio was stereo per default but wsprd requires a mono recording
The sox option for mono recording (--channels 1) is specified in the function rtl_daemon but is missing in audio_recording_daemon.
I fixed this together with my souncard name directly in wsprdaemon.sh.
By the way - the background for my soundcard loopback device is the following:
My transceiver is a QCX (an excellent kit from QRP Labs) which has an audio center frequency of 700Hz. To get the 1500Hz required by wsprd, I am using a GNU Radio script to do the frequency shift of 800Hz and this script does the handover via the loopback device.