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CED Digest Vol. 4 No. 36  •  9/11/1999

From: StereoBoy
Date: Tue, 7 Sep 1999 08:04:59 EDT
Subject: Re: CED Digest Vol. 4 No. 35
To: ceds@teleport.com

Dave Potochick <potochdj@SLU.EDU> writes:

<< I read somewhere that minidisc uses stylus/laser technology... On top of
 the disc a needle records using heat and magetism and makes the disc Magneto 
optical... Then the laser reads from the underside of the disc... So, stylus 
based
 technology isn't completely dead yet.... >>

Whoever wrote what you read had a very poor grasp on the system because that 
is incorrect, there is NO stylus technology used in the Mini Disc format. The 
system uses Magneto Optical recording, which uses a laser to read the disc 
and additionally, when recording, to heat the magnetic particles on the disc 
past thier "currie" point, which is the point where they lose thier magnetic 
orientation (around 400 degrees F). Then, from the other side of the disc, a 
magnet applies a new orientation which the particles assume. One side of the 
disc utilizes a laser, and the other side, a magnet. The magnet DOES touch 
the disc (only when recording), but it can in no way be likened to a 'stylus' 
- there's not even a 'groove' for it to follow - technically, it dosen't have 
to touch the disc, but to keep the magnetic field small, and thus the power 
consumption down, Sony chose to have it ride on the surface of the disc. 
Recordable MD's are coated with a special 'lubricant' to allow over 1 million 
record/playback cycles. The lubricant is not like the simple silicon spray 
used on CED VideoDisc's - it's actually a physical layer of the disc, bonded 
to the surface. 

So, except for the fact that they are both round and rotate, MD and CED share 
no technological similarities.

Cheers!
Ty Chamberlain

------------------------------------------------------------------------
From: KatGlen1
Date: Tue, 7 Sep 1999 19:02:41 EDT
Subject: CED and LaserDisc
To: ceds@teleport.com

Dug out my copy of "About Last Night" on LaserDisc, purchased about 15 years 
ago.  
Was watching the movie and about five minutes before it ended it locked 
up...a problem that was common with LaserDisc years ago.   Japan pressings 
were supposed to be the best, and mostly trouble free.  This was a Japan 
pressing!  There was no way to watch the rest of the movie.  I had forgotten 
what a big problem "laser rot" was.  LaserDiscs were  made up of two halves 
glued together.  After a period of time often the glue would "rot" through 
one or both of the sides.  And the disc was no good.  So I went and got a CED 
movie to watch.  Isn't it amazing that the laser didn't work but the trusty 
old needle-in-a-groove did.  Sure it skipped a couple of times but I was able 
to watch the whole movie.     Glenn