Quote:
Originally Posted by cmjones01
There is some evidence that not all cassette deck manufacturers actually used the same reference playback level for their Dolby decoding. I did some work on my Sony TC-K81, a somewhat high-end 3-head deck, and while searching the web for information on standard level tapes, found that Sony's 'Dolby' level wasn't quite the same as everyone else's - something like 235nWb/m compared with the standard 200nWb/m. I checked, and indeed the measurements specified in the service manual around the Dolby decoder chips seemed to reinforce this...
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I've never come across this. Back in the early 80's though there was a discrepancy in cassette reference level, in the high frequencies. I think BASF used a slightly different method of arriving at the reference level which resulted in their calibration tapes measuring differently from those of other cal tape manufacturers. This wasn't a Dolby issue as such but Dolby exaggerates misalignment issues especially in the highs, it would have affected Dolby tracking on machines aligned to the different standard. I think the issue was eventually sorted out.