Conference cookie::notes$archive:cd_v1

    I personally own a SCOTT 939DA CD player and have "witnessed" sounds
    but not as you describe. The sounds I hear are when are change the
    index from one end of the CD to the other. The sounds that I hear
    are the whirring of the changing speed (RPM) of the disk. But I
    can not hear it unless I am within 2 feet.
    
    It sounds to be as if you need a spindle alignment. Because the
    spindle is not holding your disks parallel to the platter you may
    have rubbing or chafeing?!? occuring. Eventually you could cause
    damage to either the CD's that you play or the rubber pads that
    hold the CD.

    My Denon DCD-1000 makes a similar sort of sound, but it is not track
    sensitive.  It is very low in volume; I can hear it only if I get
    very close to the unit and listen between cuts.  It isn't a rubbing
    sound really; more like a low hiss.  The deck has been playing great
    all this time so I assume it is part of normal operation.
    
    Initially, you may think "gee it's laser-based so it will be silent",
    but there's lots of other stuff in there.  #1 is, the disc is being
    spun.

    re:.0
    
    My Magnavox 2041 does exactly what you describe.  I usually open
    the drawer and re-position the disk on the drawer.
    
    Yeah, its a crock.  Ain't called Magnacrock for nuthin'
    
    Another trick is grabbing the tray and wiggling it to make sure
    the transport is floating freely on its springs.

    My Magnavox 2020 makes similar sounds when it spins up initially,
    and when it skips over tracks during programmed play. It doesn't
    make any noise when actually playing, though.
    
    --- jerry

    
    My original 1051 took 6 seconds to do the TOC lookup and would make
    all kinds of noises when it played, especially when loading.  It
    died after 5 days.
    
    This one had the shiping screws in much tighter and does the TOC
    in 2 seconds on all disks.  It squeels only when FF & RW.  There
    is no noise when playing, however.
    
    I suggest that you go to the store and listen to the mechanics of
    one of the floor models.  If yours is any noisier, replace it, it
    will eventually die.  Question::  where the shipping screws loose
    at ALL?  if they were it will surely die.
    
    						.dave.

>    My original 1051 took 6 seconds to do the TOC lookup and would make
>    all kinds of noises when it played, especially when loading.  It
>    died after 5 days.
>    
>    This one had the shiping screws in much tighter and does the TOC
>    in 2 seconds on all disks.  It squeels only when FF & RW.  There
>    is no noise when playing, however.
>    
>    I suggest that you go to the store and listen to the mechanics of
>    one of the floor models.  If yours is any noisier, replace it, it
>    will eventually die.  Question::  where the shipping screws loose
>    at ALL?  if they were it will surely die.
>    
    						.dave.

Well, this doesn't seem as bad, the screws were tight (one screw slightly
looser than the other but tight enough to be secure), and it reads TOC in 2
seconds or so. But the noise, which is distinctly different from the squeal
made during FF and RW, sounds like it might indeed be chafing or spindle
alignment. I think I will take the suggestion of bringing it back or
at least listen to the one in the store.

I'm especially glad to hear about a 1051 that doesn't make noise during
playing. 

-Meyer

    I have the same problem with my 1040. I called the Noth American
    Phillips Repair Center in Burlington (where you take the thing if
    it's busted). The person who fixes them says the noise is normal.

Thanks to  you  all. In reply to .7, I took mine back and got another and it
makes  the  same  noise!  Maybe  on  the 1040/1041/1051 series, it really is
supposed to!

    Mine really does make the noise you describe, yet continues to work
    fine.
    
    What I've noticed is that the chafing sound mostly happens with
    CDs that have a ridge on the data side, near the inside of the disk.

Do you have any idea why there is sometimes a ridge?

    re .-1: I think it has to do with the two major processes used to make
    CDs. 

    One method (which I will call the Sony Method) starts with injection
    molding single CD blanks at a time.  The "bottom" (laser reading side)
    is molded, then aluminum is sprayed on the "top" (label side), then the
    label and clear coat is put on top of that. 
    
    The other method (which I will call the Polygram Method) starts with a
    large sheet of CDs, produced by pouring the plastic into a mold.  The
    entire sheet it then aluminized, then punched out like cookies, then
    labelled. 
    
    The Hanover, West Germany (Polygram) plant used to be the single
    largest producer of CDs (this may not be true any more- does anyone
    have up to date information on this?).  All other plants in Japan,
    Europe, and the USA use the Sony Method.  It is easy to tell a CD
    produced in the Hanover plant since the aluminium goes all the way to
    the middle; and it has no ridge since it it not injection molded like
    the Sony Method CD is. 
                                       
    GAS

I also have a DENON DCD-1000 like .2 and have experienced the same high
frequency hissing sound which changes pitch between tracks. The sound is
audible at least 3 ft. away in a quiet room, but is not realy audible once
you start playing. Otherwise the deck works just fine.

Since the noise still worries/disturbs me a bit, more from a principle
point of view,( i.e. is it REALY normal ?) I would be interested to hear
a satisfactory explanation for this noise.

    Our ears must be different - I can only hear it from a foot or so
    away.  Then again, my living room is rarely 100% quiet anyway..
    
    The salesman said "it's the laser" when I asked him.  The units
    in the store were doing it too, so I had always assumed it was a
    feature.

    sounds like a typical answer from a salesman who doesn't know a
    laser or a cd player from a hole in the ground.
    
    	paul

    re : .11
    
    The "polygram method" -- they do *not* make a whole sheet of CDs
    at a time.  They make them one at a time, using two "stampers" -
    one with the image of the CD, and one flat. The two stampers are
    spaced apart exactly the thickness of a CD.  The polycarbonate is
    injected from the center, and flows radially outward (that's why,
    on
    some "long" (i. e., approaching 70 min) recordings, like some that
    we experimented with while working with Philips, you get a lot of
    bi-refringence towards the edges, leading to "hard" ECC errors).
    
    Anyway, the disk is aluminized (they hang them on a rack of 25 or
    so in a vacuum sputtering chamber), and the business side is varnished
     -- also individually.
    
    They then have a machine which punches the center hole.  It's
    fascinating. They use a He-Ne laser to automatically position the
    disk to around 0.01mm "concentricity" [of course, because of spiral,
    that's average], and punch the hole...Then print the label, and
    they're done.
    
    
    BTW: Philips players (read: Magnavox) make a noise starting up because
    the clamp (the little magnetic donut that holds the center of the
    disk
    down to the spindle) slips slightly.  My Philips 2020 makes slight
    noise as it spins up, but the noise disappears entirely before any
    audio begins.  I have observed many other samples of Philips players
    in Eindhoven which behave the same way.
    
    Anyway, that's the explanation given me by the folks who designed
    the transport.  It seems to be borne out in at least the cases I've
    seen.
    
    /don feinberg

    And -- I should have said this in .-1 ....
    
    One of the real problems with the Sony method is that the center
    hole is injection molded as part of the "stamping" -- which is
    otherwise technologically close to the Philips/PolyGram method.
    Sony had *much* trouble getting good concentricity this way early
    on...and because of the more difficult injection process, had even
    more birefringence problems than Philips did.  Sony gave me one
    of their early sample disks (which I still have) that exhibited
    this.  Hard ECC errors out around 67 minutes....
    
    /don feinberg
    

    re .15, .16: Apparently I was misinformed about the "Polygram" process.
    Thanks for the information.  Did you do some work with them for
    CD ROM or something?
    
    BTW, if the Sony Method is so prone to problems, why is the Hanover plant
    the only known (to me) plant that uses their method?  Is it a licence
    problem or what?  
    
    Also, do you know how the Sony Method aluminizes?

        also re .15/.16
        
        What have you got that you use to find hard errors? Would it also
        check for bad data on our audio CDs? I hear that they aren't as
        good as some would like us to believe. 

    There is a "Gutenberg Process" pilot plant for CD's out in CA, which
    actually does work by calendering (read "denting") a thin, chemically
    softened sheet of polycarbonate, then laminating it at low temperature
    to form tiny bubbles.  The bubbles act like pits when hit by a scanning
    laser.
    	 
    It's only a pilot plant, though.  See "Digital Audio" about a year
    ago (I think) for an article on the process.
    

Back to the original question...

I just purchased the Sony D7 portable and noticed a rubbing/chaffing noise
like the noter in .0.  More noticeable when it started up than later into
the CD.  So I experimented...conclusion:

When I place the CD into the unit as level as I can and close the lid I hear
the noise.  If I place the CD into the player with the edge closest to me
almost touching the bottom plate(READ Bottom of the inside housing), I don't
hear it.  Diagram follows...

Side view of spindle insides...
					\
					 \
					  \
					 \ \
					  \-\
				    A ---> \ \
					      \
				B -----+       \
				       v	\
			|         ------        O  <---Hinge
			+-----------++----------
Bottom of inside housing--^

Description using diagram... In my 'playing with' the player, I felt that when
I placed the CD level onto the bottom spindle in the player that when A + B
met they would tilt the CD back into the machine.  I placed the CD into
the player level (-) it would tilt back like (\).

When I placed the CD into the player like (/), when A + B met they pulled the
disk into (-) place.
(Disk within unit --> (-) = Level, (/) = tilted forward,(\) = tilted back)

This is what I have found so far.  Tilting it forward has proven the best way
to put the disk in such that no rubbing/chaffing noise is very noticable.

What can you do in a table-top to prevent this, I don't know!  :-)

Dan

    
    I don't think a tabletop unit clamps the same way.  The D5(7) models
    have to hinge wide to allow access, but a tabletop only has to hinge
    enough to let the disc in and out. (except the early Maggies).
    
    						.dave.

    re:  .18
    
    I've used two ways:
    
    One -- my Philips player has a little LED on the front panel. It's
    connected to the line from the ECC chip that goes high on a "second
    level" ECC error, i. e., the base machine ECC failed to correct
    a detectable error.  Light goes on and machine halts.
    
    (BTW: on the drives that DEC gets from Philips for CDROM, that same
    line is used to trigger the second-level (i. e., the ECC we imposed)
    over the hardware (drive-level) ECC in the CDROM controller.)


    Two: I have also had some experience with some instrumented drives Philips
    has had which "dump" the disks.
    
    To directly answer your question:  there's no easy way,
    depending on the player in question.  Since the ECC strategy
    (strategy :== the microcode algorithm/implementation for ECC)
    and tracking systems vary so much from player to player, disks which
    show up as having hard errors on one player will not necessarily
    have a problem on another player.  So it's hard to even talk about
    disks "with hard errors".  What I meant in my original reply was
    that the Sony disk would not play for Sony or Philips; it also will
    stall on my Philips player (as expected).
    
    In general, one way to tell is if an otherwise reliable player just
    stalls (or if the output goes to zero momentarily). As a heavy-duty
    generalization (at least in the case of Philips and Sony players): if they
    continue reading without interruption, the data is corrected
    within the limits of ECC dectability.

    Does this help?

    /don feinberg