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Different Dolby levels were mostly from the U.S. where too many people never understood that the Dolby A system depended on the noise at 185 flux levels to mask its activity.

On the other hand many people were never willing to pay for real alignment tapes. I remember getting in 24 track tapes all the time from other San Francisco studios that had the same channel recorded at the wrong level compared to both tapes from LA and our alignment tape.  I always wondered who started passing the screwed up tones around town.

Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.562.4346 http://www.bobolhsson.com http://audiomastery.com


-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Fred Thal
Sent: Saturday, January 15, 2011 11:58 AM
To: [log in to unmask]
Subject: [ARSCLIST] Dolby A-type level standards

Apologies if my following points have already been made by others. I only occasionally look at digest versions of this list.

Tom Fine writes:

> I've run into the same thing with Dolby A reels, with azimuth aligned 
> with a scope, the level-set tones are sometimes lower than expected and in those cases it's great to have Dolby tones to get > the CAT22 to track well on decode. I've always ascribed this to self-erasure over time.

I think you are mistaken. There have always been differing standards for what constitutes Dolby level. It is hardly uncommon to see Dolby A encoded tapes recorded at different fluxivities.

Regarding describing azimuth as being aligned with a scope, this is always somewhat ambiguous unless you also state whether you mean that two tracks were aligned for minimum inter-channel phase difference, or that one (or both) of those tracks were aligned for peak short wavelength amplitude response.

Fred Thal
Audio Transfer Laboratory