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In Reply to: RE: Zerostat posted by JURB on October 15, 2016 at 12:56:03
" Stamped CDs work by the pits being ¼ of the light wavelength deeper, causing the light to null out. Burned CDs work by a photographic layer that blocks the beam to emulate those pits. Static is not geerally a problem. "The CD system does not work like that. What does " causing the light to null out" mean?
CD "works" at the light level you appear to be referring to by sensing the phase difference of the reflected laser light from the pit compared to that from the land.
The CD itself is prone to storing static electricity being made from polycarbonate. The optical collimator assembly is mounted in a very sensitive assembly that moves up and down to keep focus as the disc rotates. It is very lightweight and could feasibly be attracted by static electricity (just like paper to a charged plastic surface) to the disc causing it to adjust to keep focus which may affect the sound (additional demand on the power supply?). So using any form of de-static device including a Zerosat could help improve matters.
Edits: 10/15/16Follow Ups:
" Stamped CDs work by the pits being 1/4 of the light wavelength deeper, causing the light to null out. Burned CDs work by a photographic layer that blocks the beam to emulate those pits. Static is not geerally a problem. "The CD system does not work like that. What does " causing the light to null out" mean?
CD "works" at the light level you appear to be referring to by sensing the phase difference of the reflected laser light from the pit compared to that from the land.
The CD itself is prone to storing static electricity being made from polycarbonate. The optical collimator lens assembly is mounted in a very sensitive assembly that moves up and down to keep focus as the disc rotates. It is very lightweight and could feasibly be attracted by static electricity (just like paper to a charged plastic surface) to the disc causing it to adjust to keep focus which may affect the sound (additional demand on the power supply?). So using any form of de-static device including a Zerosat could help improve matters.
Edits: 10/16/16 10/16/16
"The CD system does not work like that. What does " causing the light to null out" mean?"
Though light acts like a particle sometimes it also acts as a wave. It has a wavelength. When you move the reflective surface ¼ of the wavelength of light the reflection is ½ a wavelength off and it nulls out. Read up on wave theory. This is from the Sony book. I might still have it and could scan it and send you the pictures. This was factory training back when they first came out.
The LASER pickups were slightly changed with the advent of burnable CDs because they use a type of photographic film and the original players could not read them. They were further redesigned when CD-RWs came out because a bunch of them could not read the RWs.
Stamped CDs still have the pits ¼ wavelength of light down for the nulling effect. Burned CDs cannot compete with that contrast ratio. Also, since a burned CD works by photography pretty much you can't leave it out in direct sunlight, this will not bother a stamped CD.
Static electricity will not bother either as far as I know. With vinyl the problem was the mini arcs between the vinyl and the stylus. With a CD the LASER ever gets close enough for that.
Also if you feel like reading maybe you can get a copy of Principles Of Digital Audio, written around the time CDs came out. It says that CDs could easily be four channel, it is just that they never mass produced the media or the players with that feature.
If it's true the Plastic CD builds up an electric static charge whilst spinning why wouldn't the static charge return rather rapidly after the disc has been neutralized before play?
Good point and I am sure that this probably happens so that the end of the disc is no longer as effectively treated. And, of course, when making comparisons people will be comparing from the start of the disc or from an individual tack i.e. before the effect is compromised.
This is why, when I was seemingly most affected by this issue, I used a static neutralising fluid which dries on the label side and seems good for a number of plays. BTW the best liquid for this is Teepol industrial detergent , for which a few dollars ( or pounds in my case) will get you enough for a lifetime of CD static neutralising ( and probably for your friends too). It comes in 5L packs for around 8.50 GBP or , with the pound's dive, that'll be around $9 (if not now check later in the week)! Nordost do a liquid for around 30-40 USD for something like 25CL in a pump spray. Strangely Teepol and the Nordost product have identical smells. I'll say no more.
BTW, your criticism also seems valid to me for the Zerostat's original purpose of treating LPs.
I use industrial long lasting anti static spray on CDs, cables and carpets. The theory why a static charge is unwelcome on interconnects seems a little vague, however. ;-)
"So using any form of de-static device including a Zerosat could help improve matters."
I agree. And you did a good job explaining the (IMHO) most likely mechanism.
I did, or at least started, an experiment years ago using a zerostat to place local charges on a CD which I was then going to play and see if I could see the charges by monitoring the focusing servo current while the disk was playing.
Well.. I never got around to doing the second step but I monitored the charge locations using a doghair electrometer for a few days and they were very stable, charges really persist in polycarbonate. However using the zerostat properly they were easy to remove.
A doghair electrometer (cat better?) is a hair taped to a toothpick and sticking out maybe 1.5". You just touch a spot on the disk (on the transparent side) to pick up a reference charge then you can see the relative charge on other areas by holding the tip close and watching it bend.
Regards Rick
Put the back of your hand to a cd in the winter when it's dry. If the hair stands up you have static. I use my Zero Stat on cd's.
bigshow
Isn't the CD holder grounded within the unit?
I believe that the laser diode in the OPU is grounded for protection before installation. This ground may defeated by breaking a solder bridge upon installation and which then allows for operation. I assume that there is accordingly some form of grounding path created thereon.
However the collimator lens assembly itself is decoupled from the laser and the rest of the OPU so as to be able to move and to change focus. I would imagine that due to its size, lightness and need for freedom of movment (in the vertical plane), grounding may be hard to achieve for this component which would leave it free to be attracted by static charges. Unlike the laser diode there would not be any risk of damage, however.
The CD disc itself is normally only held around the edge of the centre hole on a form of chuck which is, in turn, attached to the motor spindle. There may be additional clamping applied but whether any attention is paid to grounding I do not know.
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