How often do you demagnitize your MC cartridge?

Copper is not a magnetizable material. It cannot become magnetized. The coils in a cartridge are made of copper, usually very high purity. The magnetic action that acts on the copper coils is an inductive process that does not result in any "permanent" magnetization of the copper. It simply induces a current in the copper coils in an electromagnetic process like a generator. Copper is not a material that can become magnetized. Copper transformer windings don't become magnetized, copper speaker voice coils don't become magnetized, copper commutators in generators and alternators don't become magnetized, and copper coils in cartridges don't become magnetized.

Why would there be a need to de-magnetize something that is not magnetized in the first place? Now, maybe there is something else around the cartridge, like the screws or other hardware that can become magnetized, but not the coils.

Tom, you forgot to mention magnets that are present in both MC and MM cartridges otherwise there will be no emf i.e. electro-magnetic force.

Gmorris,

Lyra Helikon manufacturers quote the following:

The Lyra Helikon uses a polepiece-less magnetic system. The signal coils operate in a magnetic field created directly by two powerful, precisely shaped disc magnets of nearly equal size, mounted fore and aft of the coil gap - in the simplest and purest manner possible.

I'd say proceed with your ehem... confidence of demagnetizing I guess these valuable magnets that is a part of cartridge's structure and continue to trust ehem... "engineers"(I guess from the Immedia distributor domain).

Marakanetz, yes of course there are magnets present in the cartridges. But they do not cause any permanent magnetization of the coils. They cause the coils to be energized by the movement in the field, and induce a current. But, when movement stops, the signal generation stops, and no magnetizing force is left residing in the coils, other than that which is created by the magnet's fields.

However, there is some possibility that there is some content of nickel or other magnetizable metal in some of the solder joints. That could become magnetized. However, I really think that is a low possibility, and would only comprise a negligable amount of material that could be magnetized extremely weakly, and is not in the vicinity of the main field anyway. I think that is not a real factor in this, but I mentioned it anyway.

That's right, you don't want to de-magnetize the magnets (or even attempt to do so)...this may be the exact issue that I eluded to from my research. In essence, continued attempts to de-magnetize the magnets would weaken the electromagnetic fields (or worse, change their characteristics) which would intern reduce the inducted current, etc., etc. causing all kinds of issues with the final signal information.

Thanks, Twl!

Wes

"A little knowledge is some times quite dangerous" so says the old adage. “Fellas”, we are taking about traces of residual magnetization in the coils. So called “pure Copper” coils may have traces of iron or other magnetic materials. After prolonged usage the trace molecules will align themselves into magnetic domains. The net effect is a perturbation of the magnetic field intensity created by the fixed magnets at the position of the coil (the resulting field is the vector sum of the field from the magnetic dipoles in the coil and the field from the fixed magnet). Demagnetization attempts to make the orientation of the dipoles random thus rendering the coil un-magnetized (the sum of the B field is zero, because the random orientation of the magnetic dipoles leads to cancellation.)

I agree that frequent demagnetization may be detrimental to the cartridge. However, I feel strongly, that many cartridges benefit from periodic demagnetization.