When to do the cartridge demagnetization

[mahiruha]

Hi Guys,
have any of you tried cartridge demagnatisation or rather how do we know when to do it. I found this interesting video which shows how to do it easily. I am wondering has anybody tried this trick or rather does it make sense to do it that way?

Cartridge Demagnetization - YouTube

Thanks.

 

[stevieboy]

Hi Mahiruha,

I have a cardas test record with demag tracks but have never used it. Van de hul says demagging will reduce the Weiss complexes and then you need to keep doing it more and more regularly cos you reduce the magnetic something. refer to the galencarol site I'll try digging up the link. Can't open the video right now but am guessing it's the one of the audio dealer doing it with wires right? So short answer for me, never.

Regards


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[stevieboy]

Furthermore, contrary to the conventional wisdom, A.J. van den Hul sternly advises against fluxbusting your moving coil cartridges. Van den Hul avers that degaussing a cartridge reduces the number of magnetic complexes in the magnet for all moving coil designs. On one hand, fluxbusting helps realign the magnetic complexes which become more disorganized over time. On the other hand, the cure may be worse than the disease because fluxbusting reduces the number of Weisz complexes and realigns the atoms into larger, less refined aggregates. The end result according to van den Hul is that you need to fluxbust your cartridge more and more often with a gradual decrease in overall resolving power. So, while a cartridge may sound better after each degaussing, its resolving power will gradually decrease due to incrementally coarser reorganizations of its magnetic complexes. Or as A.J. would say you will end up having to degauss your cartridge after each Beethoven symphony. A.J. van den Hul B.V.

Mahiruha, at the end of the article http://www.gcaudio.com/resources/howtos/ttsetup.html

Regards


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[mahiruha]

Hi Steven,
thanks for that link. Well To be honest what A.J. van den Hul said in that article kind of make sense but I nned to read up about the working principles of moving magnet and moving coil cartridges before getting a absolutely clear picture. I faintly recall from my physics courses in school these things has to be related to electro magnetic induction so in order to change the polarity of the magnetic atoms some sort of voltage variation has to be there to change something. I don't really understand how just playing track like cardas test record can demagnetize a cartridge. Anyway I am in no hurry to try it but just curious if anybody has tried it and what are the results.
Thanks.

 

[santhosh]

Mahiruha & Stevieboy,
Stop scaring newbies with all that ^ gyan. IGD, Demagnetization, Degaussing, wazdatname etc.

Just kidding guys, keep it coming. One year into this Vinyl hobby and still learning from your discussions:cheers:

 

[stevieboy]

Hehe there's something bad in the magnetic coils, who you gonna call fluxbusters! Had a funny experience today morning. Plumbers came over to fix hot water one guy saw lps lying around and he was looking all wide eyed with respect after that. Was telling me these sound better than DVD. I said yes. He wanted to know where to buy how much a player was etc. After that when leaving full awe shaking hands and all. So next weekend they coming with the taps and have promised them an audition ))) they quite excited. vinyl rules! Grin


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[mahiruha]

Hi Steven,
Done some reading and things are rather clear. First lets see how a moving coil cartridge operates.

Moving coil cartridges
The first cartridges with Hi-Fi specifications were developed in the mid-forties and were of the moving coil design. In general, moving coil cartridges are more expensive than magnetic cartridges and they do not, therefore, enjoy the same popularity. However, the most demanding Hi-Fi enthusiasts remain loyal to the moving coil design because of its great linearity and lower distortion.
Compared with a moving magnet cartridge, the reverse principle is applied in the moving coil cartridge. Here, a powerful fixed magnet is used and the coils are mounted on the cantilever itself. When the coils move in the field of the magnet, they cut the flux lines of the magnet and voltages are generated in the coils. (Fig. 6)

(Fig. 6.) Moving Coil cartridge principle. The coils on the cantilever move in a powerful magnetic field, and voltages are generated by induction.
Once again, with a moving coil cartridge it is important that the moving parts be as light as possible. Therefore, there are only relatively few windings on the coils, and the output voltage from a moving coil is generally so low that it cannot feed a conventional amplifier without special steps being taken.

The problem is after a prolonged use of the cartridge the cantilever becomes magnet themself as they are always staying in the close proximity of other magnets. Which is quite common. To have a better idea what is happening here it is good two see the following video.

Methods of Magnetisation and Demagnetisation - YouTube

See the video from 7 minute onwards to understand how to demagnetize a magnet by passing ac current which is slowly decreasing in magnitude.
So we understand that basically to demagnetize a magnet we need to pass the ac current through a wire which is wound around the magnet.
Now in our case of a moving coil cartridge we have wires coming out of the moving coil which is sending the current to the preamplifier through the tone arm cable. So in order to demagnetize the cartridge we are actually demagnetizing the cantilever over which the coil is wound.

Now in the original youtube demagnetizing video what is happening is when we are touching the hotpins of the RCA cable we are actually making a closed circuit and as the styles moves in the grooves of the record again current (Not purely AC depends on the Groove and I think a properly designed grrove can generate perfectly decaying AC current) is generated because of electromagnetic induction which is passed though the coil and it demagnetizes the cantilever.
Now if I understand correctly if we do it this way there no way possible to increase or decrease the magnetic properties of the permanent magnets of the cartridge as they are not part of the circuit. So this method should work beautifully.

Well the above is my understanding from basic reading. But I am not too sure about the internals of the cartridge. Moving magnet cartridges are completely diffrent story so above theory is not applicable there.
Thanks.

P.S A good into to electromagnetic introduction is in the video

Electromagnetic Induction - YouTube

But it shows how a moving magnet cartridge works. Moving coil works just the opposite.
Thanks.