arsclist ELP Laser Turntable; Full 3-D mapping of groove?

[Jon Noring <jon@xxxxxxxxxxx>]

George Brock-Nannestad wrote:

>Now, if the signal were cleaner from 
>the outset, such as from the ELP Laser Turntable (which has no 
>inertial parts), then there would be no need for this sophistication. 
>So, it is really a question where you want to put your money: in 
>hardware for the ELP or in software for the CEDAR.

I've always been intrigued with using a laser for transfering 78's
because of the inertial interaction between the groove and the
stylus, which as George noted becomes a problem when the stylus
encounters groove damage, abrasive particles in the shellac, dirt,
etc., etc.

So I found George's comments extremely interesting.

I just went to ELP's web site and it is definitely an interesting
piece of hardware. So the obvious question is how well does model
LT-1XA perform in playing 78s? Can it handle slightly warped or off
center disks? What are the other "real world" problems with it for
transfering 78s?

On another note, having worked as an engineer at three DOE National
Labs, and alongside several scientists who did laser doppler
velocimetry and similar laser techniques, I've always been intrigued
with the obvious next step: to use laser techniques to accurately map,
in three dimensions, the groove of a shellac disk. Once mapped, it is
conceivable to then "play it back" in a computer and reproduce the
wave form. The advantage of this is that all the spatial information
of the groove becomes known, and it may be possible to compensate for
various types of groove damage, abrasive particles sticking out in the
shellac, record warpage, etc., etc. -- in essence to be able to
reconstruct the groove near to its original pristine form as originally
mastered.

The fundamental problem with running a stylus through a groove is that
all this intricate 3-D detail is lost -- the stylus integrates these
three dimensions essentially down to one, and adds insult to injury by
adding artifacts of its own to the signal! It is a massive loss of
very useful information.

Obviously, a groove mapping technique would be an expensive proposition
to research and develop, and probably to even operate (has somebody
already tried this?), so it may have limited use, maybe for extremely
rare and noteworthy recordings where a master pressing or a shellac
pressing in E condition or better is not available. There's quite a
few researchers at the National Labs with the requisite backgrounds
who would find this to be a real interesting problem and may consider
exploring it on their own time with minimal or no funding, at least to
research the feasibility of it for writing a cogent proposal. There is
a lot of interesting technologies which have been developed at the
National Labs over the years.

Comments? Criticisms?

Jon

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