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Charles Lawson wrote:

>"Michael H. Gray" <[log in to unmask]> writes:
>  
>
>>I'm curious to know how master tapes 'deteriorate' Is it in the physical 
>>carrier or in the magnetic signal?
>>    
>>
>
>Both.  Depending on tape stock, materials and storage, the tape itself may
>degenerate over time causing drop-outs or worse.  (There have been many
>extensive discussions of the hydrolysis problem associated with tapes from
>the 70s and 80s, for example.)
>
>Also, magnetic tape recording itself is inherently unstable.  Those
>magnetic domains don't just sit there for all eternity in the same
>configuration as when they were recorded.  They are easily influenced by
>temperature and external magnetic fields (including that of Earth itself)
>and will tend to randomize over time.  If the tape was recorded at a high
>level, layers of audio will print through from one to another and this
>problem tends to get worse the longer the tape is sitting there. 
>High-level recordings also have a greater tendency to exhibit increasing
>distortion over time.
>
>It goes on an on...
>
>Some references here:
>
>http://www.clir.org/pubs/reports/pub54/2what_wrong.html
>
>http://www.sonicraft.com/guide.html
>
>and there are lots more.
>
>People like Richard Hess have spent substantial chunks of their lives
>dealing with these issues and can give more detailed explanations than I
>have time for today, alas.  It's all very interesting and can take down to
>quantum mechanics, if you like!  (Aside from being an expert, Richard is
>also a really nice guy!  If you need a tape transferred, go to him.)
>
>--
>Charles Lawson <[log in to unmask]>
>Professional Audio for CD, DVD, Broadcast & Internet
>  
>
I was aware of all of these problems (I deal with them everyday in my 
professional life) but I am not sure that the original statement about 
an LP eventually being more 'faithful' to
the 'original sound' of the master tape is any more than a fanciful 
supposition ... unless, of course, you've exposed your masters to stray 
magnetic fields ... in which case, you're not
taking good enough care of your tapes to begin with.

Mike

cf. Cuddihy, Edward F. 'Aging of magnetic recording tape"  IEEE 
Transactions on Magnetics, Vol. MAG-16, No. 4, July 1980: 558 - 568.