Discussion about vintage cassette tape degradation

[20tajk7]

Hi Werner and welcome to Phoenix.
Once recorded a That's CD-MH at type IV position on an AL-300.
It was possible to calibrate it at type II position but doesn't sounded good, so I tried type IV, calibration worked by reducing the bias close to minimum and that('s) sounded better.
I think rec eq peaking made the difference.

 

[overmodulated]

What are you sniffing, actually? A crayon smell is typical for chrome. Maxell have not made a chrome tape since the 1972-1975 'CR' model. Since then, starting with UD-XLII, all were ferro-cobalt. As most other Japanese manufacturers did.




Barring extreme storage conditions ferro-cobalt in general ages rather well, although some heavily polished tapes (post-1986, generally) are prone to mechanical surface damage.

And what is this with 'hard biasing'? When deck and tape are healthy, and the tape lies within range from the deck's central biasing point, then it works, end of.




It has been conclusively proven in the past few years that chromium dioxide, as used in tapes, is chemically instable and decays with time, even when properly stored, resulting in signifantly aberrant recording parameters and performance: treble sensivity goes down, MOL goes down, distortion over the top 10dB range goes up, compression goes up.




HD8 is a metal-enriched ferro-cobalt. Just like the few others of this breed (TDK, That's) it is characterised by abnormally high sensitivity, high SOL, and high bias noise, pushing it far away from regular IEC type II behaviour.

I know the smell he’s talking about, I have more than likely the same mid 80s Maxell XL II tapes, and although they’re not pure chrome, they definitely have that smell like the BASF chromes. Although I understand chromium dioxide is odorless, it’s one of the precursors/chemicals used. So those Maxwell tapes which I assume are ferric cobalt, probably used some of the same chemicals in the process. I know someone mentioned that they don’t remember that crayon smell when these tapes were new.

Mine are hit or miss as to whether they bias correctly on both of my 3 head decks, but I can get 7 out of 10 of them biased correctly. It seems my BASF chromes, and TDK SA tapes aged better, but of course everybody’s experience is different. Definitely not perfect on 40+ year-old media, but much better than the new media in my experience.

One of my favorite tapes are the Maxell XL IIs tapes, they still sound phenomenal and maybe because they’re not quite as old. Also my TDK SA tapes have aged very well, and still bias easily, they are tough to beat for sound quality IMO.