[ProAudio] FeralA - Recordings released encoded with Dolby A

[Richard L. Hess]

My colleague in the software decoder for recordings made with Dolby A 
noise reduction has been very interested in commercial releases that 
appear encoded.

He has spent a good deal of time researching this. Thankfully, he's 
spared me most of the listening, but he's getting very good support from 
some online audiophiles, including one, I think, who writes for The 
Absolute Sound or something like that. I can hear the difference in the 
samples he sent me.

The premise is that many albums were released without proper Dolby A 
decoding.

I've been told this is the case for a few albums, including at least one 
recent re-release which was mixed undecoded from the Dolby A multitrack.

What makes this more interesting is that he's finding a handful of EQ 
curves need to be applied to the recording prior to decoding.

He has also found that many/most of these decode better as 
Sum/Difference (or MS).

He thinks that there might have been a reference document in the 
mastering industry--it is that consistent.

Does anyone know anything about this, or is it just happenstance?

We don't think it's a common failure mode of old decoders--but it 
appears intentional.

I know this sounds crazy, but there seems to be experimental support for 
this and the consistency of it is interesting.

Does anyone know of any processes that were used in mastering back in 
the 70s that might create this. We don't think it's the Aphex Aural 
Exciter--that is a different kind of annoyance for my colleague. He has 
done some experimenting on a De-Exciter.

Example artists are Linda Ronstadt, Olivia Newton John, and to some 
extent Abba.

One of the reasons I've not attempted to shut down his FeralA 
experiments is that it has led to better finessing of the parameters and 
better decoding of real Dolby A recordings.

Thanks!

Cheers,

Richard

-- 
Richard L. Hess                   email: richard at richardhess.com
Aurora, Ontario, Canada           http://www.richardhess.com/
http://www.richardhess.com/tape/contact.htm
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