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MMD > Archives > March 2000 > 2000.03.01 > 05Prev  Next


Phono Record Reproducer Uses Laser Beams
By Mark Kinsler

This was posted to the How Things Work discussion group by Nicholas
Bodley.  I've edited it a bit.

Mark Kinsler -- a long-time admirer of Mr Bodley.
http://www.frognet.net/~kinsler

 [ A variation of this laser beam technique might be used to transcribe
 [ the music from the tiny pins of a music box cylinder!  -- Robbie

 - - -

A Japanese company is building (by hand) laser-pickup turntables for
vinyl LP records.  Not new tech, but commercial success is.  Flutter
and wow specs are not given, but are more than likely non-zero.  Has a
linear traverse and can accommodate a reasonable amount of warping.

The groove angle has to be 90 degrees, so there might be some double
reflections.  Five beams: two for audio, two for tracking, and one
for height (fairly sure).

Dirt particles are a major problem; the package includes a US-made
washer/vacuum cleaner. (Heck, if you can afford this turntable why
not buy a tabletop clean room to play your LPs in?)  Seems that dust
particles are almost as bad as uncorrected digital errors in the
data bits of a digital playback [like CD and DAT].

Frequency response is 10 Hz to 25 kHz, with a rolloff beyond 25 kHz.
Apparently it sounds just peachy.  (The most advanced cutter heads are
helium-cooled, and driven by amps capable of several hundred watts per
channel. Fairly sure they have position feedback. This is old info...)

Cheaper version (nominal 33.3 rpm, but with wide range about that)
is $13,000 or so US$. The $20K version plays nominal 78 rpm records,
with again a wide speed range (60 to 90 rpm, iirc.)

Requires black LPs.  For mono records, lets you select the inner or
the outer groove wall.  Laser lifetime is estimated at 10K hours.
See http://www.elpj.com/article.html

Nicholas Bodley * Waltham, Mass.


(Message sent Wed 1 Mar 2000, 16:39:39 GMT, from time zone GMT-0500.)

Key Words in Subject:  Beams, Laser, Phono, Record, Reproducer, Uses

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