> I don't know the parameters for old or new vinyl used for LPs, but in theory
> there could be a stylus pressure light enough to cause no damage. If allowed
> to rest between playings, as Paul notes.
A couple of the companies that provided music programming to radio
stations were extremely anal-retentive about these things. Generally
speaking, they found the second or third playing to be the best one.
However, for the "master discs", those that were cut and not pressed,
those deteriorated just looking at them. Most of these high-end
operations had extremely expensive turntables and cartridges and were
as perfectly balanced as could be.
> I've wondered why no one seems to have developed a laser groove reading
> system.
I saw one of the Finial laser turntable prototypes that was used by
one of the above mentioned companies. The problem was the extreme
noise it produced in pops, clicks and a tremendous about of
low-frequency artifacts and pitch shifts as it couldn't "ride" the
groove, nor could it push its way through micro dust specs. The
followup ELP was much better and addressed everything but the clicks
and pops. I'm not sure if this one feature ever made it into
production, but the prototypes we tested allowed us to adjust the
depth in the groove to read. The read lasers in the prototypes had an
adjustable width and aim. If the record had wear patterns, you could
adjust the depth to avoid it. And if you kept the laser depth wide, it
would average out the signal across the entire groove wall, which
almost totally eliminated the clicks and pops. One of the prototypes
even allowed us to adjust the angle, which addressed the common
problem of a played record would have the wall distorted, by having
the "bumps" pushed down the groove by the needle. With the angle
adjustment and the increased read depth, we could align the laser with
a portion of the worn groove with the unworn groove. Tricky stuff, but
without advanced automatic controls, none of this was really
"user-friendly" enough for most any consumer. Great for remastering
engineers, but lousy for enjoyable playback. I actually installed two
of the preproduction units here in the USA and got to train the
mastering engineers on it. (true golden ears). But we used them for
front-ending into digital editing systems for remastering.
Funny how NDAs work. I haven't been able to say squat about this, but
a quick search on Wikipedia and Google revealed all this, so you can't
blame me.
AG
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