Conference napalm::guitar

    There's alot of discussion on this (and the use of armor-all on CDs)
    in the CD conference...
    
    My opinion? You can't get a warmer sounding CD with a green magic
    market. You need either orange or bright yellow...
    
    Edd
    

    Sounds like a bunch of baloney.  
    
    Think about it.

    �   The phenomenon at this writing cannot be technically 
    �   explained...
    
    Starts off with the truth, anyway.
    
    �   Gone, too, was the harshness often associated with 
    �   digital software.
        
    Wait a minute.  Is this some kind of a joke??
                               
    �   ...though I can't say if the green coating actually 
    �   improves dynamic range.    
                 
    Oh.  Can only state solid facts like "seemed smoother", "clearer",
    "glorious", "precise", "articulate".                
       
    �   The light from the laser beams in optical disc players
    �    is not completely absorbed by the shiny metal discs.
    
    ... and its a good thing, too! 

    Really, this is a funny one.
    
    							Marc

    
    Well....I have to say it sounds daft to me too.  There are two things
    that I can think of immediatly that could be affected. 1) The laser
    light is filtered to a degree (although the solid state lasers in CDs
    are infra-red so I doubt the effect would be much).  2) The refractive
    index could be modified slightly).  In real terms the only thing that
    could possibly be improved is the bit error rate & it seems dubious to
    my thinking that either of the above mechanisms would do anything but
    make it worse.
    
    	Thinking on it I suppose the scatter of the relected light could be 
    increased & thus the receiving photo transistor/diode would have more
    chance of beig "hit" but the light intensity would be decreased so
    sensitivity may become an issue.
    
    	As far as I am aware (please correct me if I'm wrong) the surface 
    of a CD is like a series of little mirrors, a logic '1' mirror points 
    the laser light back to the scanning head to be detected & a logic '0' 
    mirror is angled to point the laser light at oblivion & is not detected.  
    	The lasers are solid state Gallium Arsenide lasers which "lase" in 
    the upper Infra-red & produce a beam in the order of a few microns wide.  
    
    	The whole piece of kit is a precision engineered miracle that has 
    taken years of extensive development & leading edge technology to produce 
    it, I can't somehow believe that applying a coat of green ink (that you
    wouldn't let your kids eat let alone allow near your precious music
    collection) could do anything but thow a spanner in the works.
    
    All my opinion of course:-)
    
    cheers
    		Pete

I also heard that if you dip your CD in 111 Trichloroethylene it'll 
sound almost as good as dipping it in a can of Sears Best Latex
ceiling paint !

;)

    
    It does sound like baloney.  However, at least three of us here at the
    plant have tried it and thought it helped.  It takes less time to try
    it (and it won't hurt the cd) than to argue why it doesn't make sense.
    
    -pat

    Ppphhhtt....
    
    1's is 1's. 0's is 0's. No midpoint. Anything not resembling one or the
    other gets error corrected until it does, and that happens at a point
    AFTER the Armor All has any chance to effect it.
    
    Treating the disk is not the place to try and improve the sound of your
    stereo...
    
    Edd

    I don't know anything about this stuff, but what if somehow or other
    the green stuff cuts down the error rate, so the processor in the
    cd player spends less time in correction and more time spewing data
    into the d to a end of things. Coud this conceivably affect the music?
    
    I mean, does a burst of errors -- not bad enough to cause a glitch
    but bad enough to cause lots of hard work in the correction department
    -- affect the music at all? (Maybe a given passage takes nanoseconds
    longer if it's full of errors).
    
    Richard. 

    re .8
    
    As far as I know data comes off the disk at a constant rate ie the
    speed of the disk increases as the scanning nears the centre.  
    
    	On modern machines a given data word is sampled 4 times, if an error 
    is found it looks for the data elsewhere (built in redundancy is metioned
    in the sony/phillips spec. & although not detailed I understand it to mean 
    that there is multiple copies of the data stored on the disk) if it
    can't get a definitive answer on what the data should be it "best
    guesses" using what went before & what it reckons is next.  This is
    then fed to a FIFO & the FIFO is clocked at a constant rate (48Khz) into 
    the D/A.  
    
    	The fact that there is a FIFO there means that if there are
    no errors the FIFO backs up  & the disk is holding off waiting for
    space in the FIFO,  if there are errors to correct the ECC mechanism
    has the time it takes to empty the FIFO to sort it.  The size of the
    FIFO is made big enough so that a number of worst case errors can occur 
    before the FIFO empties so there should never be any drop out at the
    A/D stage.  So based on that there should'nt be any difference on that
    score.  The serial data rate is less than 1Mbit, our gallant boys in
    the forefront of disk tech have to cope with 12 to 22 Mbits & greater
    probably these days.
    
    	Another way of looking at it is that 4 bits can easily cope with
    telepnone quality transmission & most CD machines use 16 bit
    technology.  8 bits on your average stereo would be very acceptable,
    12 bits is well into HI-FI, 16 bits is more than enough.  A drop of
    resolution by 4 bits would be difficult to detect, thats 1 in 4 0r 25%,
    so a random omission of a quarter of the information would make little
    or no difference.  Even if the green gunk cleared up the odd bit error
    I find it hard to believe the human ear could spot it, but then again
    these HiFi buffs.....
    
    Cheers
    	Pete.

    Balogna, don't mess up yer disks with a marker.
    

    re: .10
    
    FWIW, CD's are played from the inside out. I believe it's a holdover
    from the proto days when nobody knew how big the suckers would really
    be!
    
    I actually tried this ArmorAll trick on a disc I didn't care about.
    Obviously I couldn't do a real A/B and my evaluation was undoubtedly 
    colored going in, but I heard NO difference. None. Nada. Could it have
    been *me*? Of course, it *could*. But the facts don't bare it out...
    
    Edd