So, yesterday I finally got: SONY TCS-30D stereo.
semi-mint condition, a little issue in the rewind on 90 mins tapes, but not a big issue since I'll be using mostly with shorter tapes and tape loops. There is a very handy speed control and the external stereo microphone works perfectly, better than the inbuilt one which is already very good.
No background noises nor issues. I'd get another one if I find at decent price, but considering I paid 25 euro + 6 it was a miracle...
Got the Gieskes ?man+ and works amazingly, and already recorded some very satisfiying backing tracks for non noisy thing using acappella Italian Alpini songs recorded live some years ago. There is a noise button that I'm not a big fan of, but also an additional noisy background that you can level up with that is fantastic. It's a lo-fi machine, so some background humming that it can be easily edited in daw but yes I like it.
Now considering this, always from Gieskes:
https://gieskes.nl/instruments/?file=zachtemanps: so definitely given up the usb thing, totally useless concept. If anybody want any of those usb walkmen I have two spare, mostly unused for 15 euro plus postage. Maybe you can hack them somehow.