Date:         Fri, 26 Sep 2003 11:53:04 -0700
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         Rob Spencer <[log in to unmask]>
Organization: Sheriff John's Lunch Brigade
Subject:      Re: Optical Groove Digitization
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Duane Goldman wrote,

 > As an eternal devil's advocate I still ponder the concept of
 > translating a continuous 3-D analog signal into a digital
 > representation . . . many educated ears are not satisfied with
 > digital reproduction. . . Perhaps in concert with such efforts
 > {at 3-D scanning] should be an equal expenditure to improve
 > analog recording & reproduction if for no other reason as to
 > establish a proper base point.

As always, Dr. Goldman brings up points worth pondering, especially as
regards the reproduction of coarse-grooved records.  Wouldn't it be nice
to have a turntable/arm combination specifically engineered for 78
playback, as opposed to microgroove?  With proper anti-skating, at least?

More interesting is the question of digitization of the signal.  It
seems to me that the process of producing a highly accurate 3-D digital
image of the surface of a record does not digitize the signal, merely
the physical analogue of the signal as represented by the groove on the
record.

In fact, the signal need not be digitized at all with this process,
whether the virtual groove is tracked virtually or used to produce a new
copy of the record for traditional playback (both options have been
discussed on this list).  It can be kept in analog form.  One may argue
that digitizing the record surface perforce digitizes the signal, but if
the accuracy is high enough it seems to me that there would be no effect
on the signal itself.

In any event, the typical pre-tape 78 was recorded direct to disk, ore
or less, so unless there is access to the original metal parts or an
intermediate form, the record itself is the lowest-generation copy
available, so we are faced with the necessity of tracing its groove in
one way or another.  In theory, the process discussed herein would seem
to allow the most accurate extraction possible of the information
represented by the groove.  At the least, it would allow the
reconstruction of a mint copy of any record that has a groove that is
pristine at some level all along its length.  This last consideration
alone is enough to justify it for me.



Rob Spencer