@marcy311 Interesting materials, was your test with polar stereo successful?
I have done a few more tests, I found out that some solderings of this old tuner were dried out.
I suppose this old tuner just need some love to functional properly, I renewed those solderings and everything seems to work fine.
I did another test and it seems to me that the polar stereo works perfectly in Steretool.
In this video below you can see the result:
https://youtu.be/bpcDCA_DdmI (at 2:04 I play a stereo test sound, check the channel separation)
@hvz Polar seems to work very well if there is anything you would like me to test please let me know, thanks for the good work!