I am sure I did something wrong when using the utility I did not use any of the options when doing the conversion. I’ll experiment with that some more this weekendGlad it's working! I just got a Japanese tape player peripheral as part of a lot, so I'm excited about doing it from real tapes in the future.
The Japanese dump list editor tool has an option for inverting polarity, as well as a bunch of other tweaks for dealing with wonky tape dumps.
Unfortunately it's Windows only, and also doesn't work super well on English-language Windows installs: lots of mojibake. It does produce workable tape WAVs though!
Awesome I’ll try it out tonightHere it is:
NEC PC-6001 NEC TREK Demonstration Program : Free Download, Borrow, and Streaming : Internet Archive
This is for retro-computing and documentation of old hardware reasons.It is a recorded WAV file containing all the demonstration programs for the NEC...archive.org