It would be good if you could post both the original file and the edited version together, so we can hear the effect of the noise reduction.
Often I prefer to listen to recordings with some hiss than to things that have had noise reduction applied. As well as removing the hiss, the noise reduction removes some high frequency components of the sound, spoiling the character a little. But I grew up listening to a lot of audio casettes, so I might be less bothered by hiss than people who've grown up in the CD era.
Indeed, that is a good idea, Alexander.
I do not find that tapes are terribly noisy and, yes, noise removal does damage the sound. I really only resort to it when it is so hogh that removing it cannot possibly destroy more than the hiss has done. I transferred all my tapes to CD but, unfortunately, I used the computer, so, in the end, on top of the tape hiss, which was not so bad, I ended up with the noise of the fan! Filrering out the fan, I get the normal tape hiss back, but the sound is not quite what it was before. Had I had the original LPs would have been better.
Stu, My little MP3 recorder records at 192 KPs.