[ATM] Schmidt correctors: 33 RPM vinyl LPs make comeback

[Dominic-Luc Webb <dlwebb@canit.se>]

In my never-ending quest to slap the face of ATM decency and
evade ATM standards and norms, I reasoned that there could be
a future for 33 RPM vinyl LP phonographs. I noted the vast
quantities of these sitting in thrift shops that actually
work, but are no longer popular technology. I wondered if
anyone ever tried to use a timing protocol based on the
equation for a Schmidt curve to move the head across an
optical surface carrying a ball bearing to grind a
corrector. Phonographs are kind of small and convenient and
size is about right for a typical corrector. I tinkered with
one and it seemed only to really need a motion control for one
axis to get it to follow a surface according to a prescribed
time protocol. Admittedly this post probably sounds silly, but
actually, given that all but the most serious inaccuracies of
Schmidt correctors are usually made by minor aspherization of
the primary anyway and can tolerate some deviation, why not?

Part of the reason I bring this up is quite serious actually.
The pan approach, while it obviously works, typically requires
some machining on a metal lathe to make the pan. I have been
interested in alternatives, a creative process I suppose. I
reasoned that a precise timing protocol integrated into something
as simple as an old turntable that can be found pretty much
anywhere for very little money might work just as well. Has
anyone here tried or used a turntable with a timing protocol?
Would anyone advise against this?

Dominic-Luc Webb

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