Why demagnitize an optical reader?

Oh, geez. Here we go again.

Are you sure you're not reading about cassette players!

I don't see how an optical device, which is non magnetic and made from non magnetic materials benefits from a demag process. 

OhOh I feel a spurge of voodooism coming.

Correct  spatialking you cannot de-mag a aluminium substrate (CD), it's non magnetic and it's all voodoo.

You may as well go and de-magnetize all your Al-foil food wrapping or trays to make your food taste better for all the good it will do.
https://www.google.com.au/search?q=al+foil+food+trays&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjx5ZjryKzUAhVLybwKHUUaBZcQ_AUICigB&biw=1509&bih=829

Cheers George

  

One imagines the naysayers would have a conniption if people said that demagnetizers work for interconnects, just like for CDs and vinyl, you know, given that there are no magnetizable elements in the conductors or anywhere else in the interconnects. 

Here is the best explanation I have found (unfortunately I cannot attribute the source):

"I did some experiments with cd's to determine what the heck was happening. Turns out that no magic is involved. What is happening is that the disc takes on a static charge,either through spinning in dry air or just from handling. A spinning, statically charged disc is the definition of an electrostatic generator. This hash-like voltage is impressed on the laser-pickup circuitry. Of course the digital circuit ignores this noise (Well,not entirely. It does effect the jitter rather badly because of power supply noise.), but the noise is now impressed on the power supply and you can see the hash presented to the power-supply rails feeding the analog amplifier, and the cheap chips in most cd-players cannot reject this hash/noise. The better the power-supply and analog cicuitry the less effect this hash/noise and the clarifier has. No power supply built by man can completely eliminate this hash-voltage. It is best to stop it at its source. Hence the Clarifier.

This tweak is actually an ANALOG tweak; the clarifier removes the static charge from the disc reducing the noise impressed on the power supply. Most all cd tweaks affect the player in the analog domain. Remember, the CD itself is indeed a digital storage medium, but the player is essentially an analog device right after conversion. (Hell, even before conversion. Its accuracy of conversion is dependent on a clean voltage from the power supply.)

For an experiment, take your favorite cd and play it. Notice where in the image the high frequency stuff is (bells etc). Now take your disc and place it against a color tv picture tube when on (about 30,000 volts static charge while running). Now play it again. You will notice an enourmous degradation of sound. Now use the Clarifier (or a bulk tape eraser;start the erasor from about 1 foot,bring close to disc,hold near disc for about 20 secs,then move out to 2 foot before turning off,it works the same just not as convienient as the
Clarifier). Now listen again. There should be a readily noticable difference in percieved noise floor and clarity on the highs.

Tweaks like vibration damping, green ink, etc all work because the PLAYER is mostly an analog device; it just gets its initial data from a digital source."

The problem with the explanation in the last post is that the electric static charge on a CD is entirely different from a magnetic field. A demagnetizer removes a magnetic field, assuming there is one, whereas an anti static fluid or ionizer is required to remove an electric static charge, assuming there is one.

Interesting. So there is something going on with the disc magnetically? I don't pretend to have any depth of knowledge or understanding in this area, I just know that it works ;)

It has also been asserted that the inks used the non-read side of a digital disc have magnetic properties that can have a negative effect on the sound of a played disc.

I’m not a big fan of the magnetic ink theory for the simple reason the ink on the CD label could only contain trace ferrous material, at best. I.e., not enough ferrous material to produce a magnetic field of sufficient strength to affect either the CD laser or any electronic elements in proximity to the CD. And certainly nowhere near the magnetic field strength of big honking transformers such as found in a modded Oppo CD player, for example. And perhaps not even near the strength of induced magnetic fields in wire. For the same sort of reason I’m not a fan of the magnetizable metal layer theory, either, as the CD metal layers are quite pure aluminum, gold or alloys. So, there must be a different theory.

I've heard about devices that claim to do this! 
$500 for 1 unit that will demagnitize CDs, 1 by 1...

If these things actually worked, artists and bands would have their master CD and all copies of it demagnitized before shipping them off to stores...

Now I'm not saying it will never work, but if you take good care of your CDs and keep them without deep scratches, they should be play reliably each time.

Snake oil and voodoo.

These forums are full of shillers shilling it, (fuses being the biggie)

Somehow it needs to be policed better, you won’t find this sort of c**p on forums like diyAudio as the designers like Pass, Curl etc etc etc and others, shoot them down before they gain any momentum.

Cheers George