Old tape recording restoration

[mladendomic]

Hi,
Some years ago, while still being owner of a 4 track cassette recorder, I transmitted my old 1980's recordings into digital .wav files.
And those recordings are far from excellent, in technical sense. Beside hum and lack of presence, there is one dominant constant - distortion, like when the recording is too loud.
What confuses me is the fact that visually, there are no clippings in the recordings. All the peaks are healthy, with no visibly typical "platforms".
I would like to improve the recordings. So I'm in search for possible cause of the situation so I can decide what strategy to use.
Is it possible that the distortion is happening below visible peaks, that it was created on some of the quiet tracks, so it's lost somewhere inside the "body" of the audio wave?
I still have original tapes but I don't have tape recorder I used to create the recordings.
What is the nature of distortion? I know it happens as result of loss of signal. So, you don't REMOVE the distortion, but you have to RESTORE the missing signal.
Is that possible with some nowadays magic audio tool?
Thank you, all, I wish you a good day!

[mojobone]

If there's a fix for your problem it likely resides in transferring your analog tapes to digital again, using more conservative levels. If not, the distortion is baked into the analog tape and there's little recourse. Note that I didn't say, "no" recourse, but cleaning up analog noise is a lot easier than fixing analog distortion; fortunately, analog distortion is less objectionable to the ear than the digital variety, so it's possible your tracks can be salvaged, but in mastering, there are no free lunches. For example, we can reduce vocal sibilance, but that will almost certainly alter any cymbals in the mix; If there's access to individual tracks or stems, all the better. There are many analog gremlins that now have digital solutions, so it might be worth posting up an example. I'm happy to lend an ear and a recommendation, based on a half-minute or so of what you find objectionable. Hum and lack of presence are relatively easy to deal with in the digital domain, but distortion comes in a LOT of flavors.

[Tunesmith]

I don't know if you have done so yet, but the best thing to do I feel would be to buy one of those 4 track players. I bought a 4 track TEAC 3340S Reel deck just like the one I had in the 80's and have been pulling off songs from the tapes and it has been very rewarding...they sound so much better than the cassette or VHS masters I had the final mixes on, plus you have the 4 original tracks of audio.

With the vintage listings (demand) these days, it could very well be worth it!

Best,
Linda C

[Len911]

I agree with what mojo said!
the fft won't show the signal as being clipped unless it was clipped during the transfer stage, on the digital recording device.
it could be the original recording was distorted or it could be the tape was deteriorating and/or the nature of magnetic recording medium, saturation and demagnetizing the heads of the recorder , etc.
there are tools and things you can do, but the degree of success isn't necessarily assured and practical, I don't think there is a magic tool.