Hi Hans,
after debugging on another mac also with Catalina, it seams that Stereotool never asks for permission to use audio input/microphone.
That ends in a kAudio_ParamError with no reference number.
(The Console utility gives a deeper access to whats going on and are better to read than the massive scrolling "log show" command in Terminal.)
Code:
Requested application <private> has policy 0, associated category:DH1009 associated sites:(null) equivalent bundle identifiers:com.thimeo.www
Code:
{ID: com.thimeo.www, PID[40648], auid: 501, euid: 501, binary path: '/Applications/ThimeoStereoTool.app/Contents/MacOS/stereo_tool'} attempted to call TCCAccessRequest without the com.apple.private.tcc.manager.check-by-audit-token entitlement
Take care and stay healthy,
regards
MrDonT