Magnet Source/Type/Magnetic Properties

[Antigua]

They will degauss if pressed face to face, that's a fact (the opposite of face to face would be "front to back"). I first got the idea to experiment with it when someone from a magnetics company was answering questions on another forum, and brought this up. I then documented a degaussing experiment here https://guitarnuts2.proboards.com/th...co-pole-pieces . It was fairly easy to get AlNiCo 5 from over 1000 to around 600-700 Gauss, which coincidentally is about how strong AlNiCo 2/3/4 pole pieces are when fully charged. So the practical use is to get AlNiCo 2-like strength from AlNiCo 5, and you can even do it on a pole-by-pole basis, which is a great way to deal with the "wound G" string stagger issue without changing the look of the pickup, and in fact doesn't require you to even remove the pickup from the guitar at all.

[Brian W.]

They will degauss if pressed face to face, that's a fact (the opposite of face to face would be "front to back"). I first got the idea to experiment with it when someone from a magnetics company was answering questions on another forum, and brought this up. I then documented a degaussing experiment here https://guitarnuts2.proboards.com/th...co-pole-pieces . It was fairly easy to get AlNiCo 5 from over 1000 to around 600-700 Gauss, which coincidentally is about how strong AlNiCo 2/3/4 pole pieces are when fully charged. So the practical use is to get AlNiCo 2-like strength from AlNiCo 5, and you can even do it on a pole-by-pole basis, which is a great way to deal with the "wound G" string stagger issue without changing the look of the pickup, and in fact doesn't require you to even remove the pickup from the guitar at all.

Does this also apply to flat "humbucker type" magnets?
A pickup with an Alnico 5 degaussed to 600 g still would not sound the same as a pickup with A 2 magnests, would it? [

[Antigua]

Does this also apply to flat "humbucker type" magnets?
A pickup with an Alnico 5 degaussed to 600 g still would not sound the same as a pickup with A 2 magnests, would it? [

I haven't tried it with humbucker magnets. I'm sure it would degauss to some extent, but I don't know if it would be by the same amount.

In a Fender style pickup, where the AlNiCo is the core material of the coil, the grade of AlNiCo also has an impact on the inductance and the Q factor. AlNiCo 5 results in a lower inductance and a higher Q factor than the others. In a Gibson humbucker, the coil core is made up of steep poles, so all the magnet is doing is dictating the flux density for the steel pole pieces. The grades of AlNiCo change the inductance of a humbucker also, but only by a few Henries rather than a few hundred.

[Helmholtz]

AlNiCo 5 results in a lower inductance and a higher Q factor than the others.

As the electrical resistivity of A5 is lower than other alnicos I would expect a lower Q.
A4 has low permeability like A5 (both around 5) but rel. high resistivity and lowest remanence.

There is another effect involved with strong magnets and steel poles. As high flux density lowers the permeabilty of steel, stronger magnets lower PU inductivity.

[Antigua]

As the electrical resistivity of A5 is lower than other alnicos I would expect a lower Q.
A4 has low permeability like A5 (both around 5) but rel. high resistivity and lowest remanence.

The Q factor is a result of eddy currents, which are result of both conductivity and permeability. This is a test I did, the Q factors are hard to make out in this presentation, but you can see 5 being higher than 2, 3 and 4 https://i.imgur.com/VKpTUJN.png I've observed this often in testing pickups as well.

There is another effect involved with strong magnets and steel poles. As high flux density lowers the permeabilty of steel, stronger magnets lower PU inductivity.

That might be true, but testing with an LCR meter shows the inductance in a PAF clone only shift by about 20mH, give or take, depending on the magnet type, so the net effect of increased saturation or reduced reluctance is small.

[Helmholtz]

This is a test I did, the Q factors are hard to make out in this presentation, but you can see 5 being higher than 2, 3 and 4 https://i.imgur.com/VKpTUJN.png

You probably had chinese fake A4. The A4 magnets I bought on ebay also behaved similar to A2. Real A4 has low permeability like A5, but lower losses.

Obviously these are single coil measurements without integration. In such presentation higher frequency peaks get an emphasis of 6dB/octave.
The more familiar integrated response would equalize this effect.

That might be true, but testing with an LCR meter shows the inductance in a PAF clone only shift by about 20mH, give or take, depending on the magnet type, so the net effect of increased saturation or reduced reluctance is small.

With a P-90 I got the following results (@100Hz):

Inductance without magnets: 6.75H
Inductance with weak (ca. 450G) magnets : 7.17H
Inductance with strong (700G) magnets: 6.30H

So the stronger magnets actually reduced the PU's inductance.
Results may depend on the carbon content of the pole screws.

No saturation involved. Steel saturates at around 1.5T = 15000G. Rather it's typical dependance of reversible permeability on DC flux density of high µ ferromagnetic materials, first described by R.Gans, 1911, for steel.

[salvarsan]

There are two industry docs on permanent magnetic materials: the PMS-88 and the MMPA-100 which date from 1988 and 2000, respectively.
Permanent Magnet Guidlines https://www.intemag.com/images/MMPAPMG-88.pdf

Permanent Magnet Materials https://allianceorg.com/pdfs/MMPA_0100-00.pdf

The exhaustive lists of alnico and ceramic types are in the MMPA-0100 pages 7 and 12.
That these documents exist tells you that there are others and more recent ones if you're willing to search them out.

The PMG-88 covers characterization and physics of magnetism while the the MMPA-0100 is an overview of magnetic substances common within the industry.

The two primary characteristics of magnets are called remanence (Br) and coercivity (Hc) which roughly mean a magnet's free magnetic field and resistance to demagnetization. Together, these determine how much work you may expect from a permanent magnet and their product is called BHmax.

For starters, compare Alnico 5 and ceramic C5 permanent magnets :

magnet	Br	Hc	BHmax
Alnico 5	12,800	640	5.50
Ceramic 5	3800	2400	3.40

A5's lower Hc tells you it can't be made short or it will tend to self-demagnetize.
C5's higher Hc tells you that short small magnets are strong enough up to a point.

Since Alnico is electrically conductive, it is subject to eddy currents when used in a guitar pickup.
Since ceramic magnets aren't conductive, they have less high frequency attenuation when used in a guitar pickup.

bon appetit.

-hizself

[Antigua]

You probably had chinese fake A4. The A4 magnets I bought on ebay also behaved similar to A2. Real A4 has low permeability like A5, but lower losses.

Obviously these are single coil measurements without integration. In such presentation higher frequency peaks get an emphasis of 6dB/octave.
The more familiar integrated response would equalize this effect.



With a P-90 I got the following results (@100Hz):

Inductance without magnets: 6.75H
Inductance with weak (ca. 450G) magnets : 7.17H
Inductance with strong (700G) magnets: 6.30H

So the stronger magnets actually reduced the PU's inductance.
Results may depend on the carbon content of the pole screws.

No saturation involved. Steel saturates at around 1.5T = 15000G. Rather it's typical dependance of reversible permeability on DC flux density of high µ ferromagnetic materials, first described by R.Gans, 1911, for steel.

I sourced the AlNiCo rods from Addiction FX. They seems to be reputable enough. The A4 poles were not identical to the A2.

I'll have to test out the P-90 case, the idea that the inductance is higher without any magnets at all would be rather surprising.

[Antigua]

There are two industry docs on permanent magnetic materials: the PMS-88 and the MMPA-100 which date from 1988 and 2000, respectively.
Permanent Magnet Guidlines https://www.intemag.com/images/MMPAPMG-88.pdf

Permanent Magnet Materials https://allianceorg.com/pdfs/MMPA_0100-00.pdf

Neither of those documents mentions AlNiCo 4, unfortunately. It's harder to find standard data about that particular formulation.

According to this document https://www.arnoldmagnetics.com/wp-c...e-101117-1.pdf , the resistivity of A4 is the same as A2, though the permeability is lower, so the eddy currents should be a little less for A4, depending on the frequency. Then again, these spec values change slightly from one foundry to the next.

[Helmholtz]

I sourced the AlNiCo rods from Addiction FX. They seems to be reputable enough..

As already mentioned, my fake A4 bar magnets I also got from Addiction FX. Had them lab analyzed for chemical composition. They were no A4, rather similar though not identical to unoriented A5.

[Brian W.]

As already mentioned, my fake A4 bar magnets I also got from Addiction FX. Had them lab analyzed for chemical composition. They were no A4, rather similar though not identical to unoriented A5.

Crap......I just ordered some A4's from them, too.
Did you inform Dennis of your findings?

[Helmholtz]

Crap......I just ordered some A4's from them, too.
Did you inform Dennis of your findings?

No.
While I immediately found that the magnets were different from US A4 (Arnold), I didn't get a chance to have them lab analyzed until a couple of years later.

But don't forget, it's PU sound, not magnet alloy that counts. The small differences in PU inductivity caused by the magnets can easily be compensated by the number of wire turns and the differences in resonance Q are too small to be audible in humbuckers. And I don't think any typical measurement will tell you how a PU actually sounds.
I just don't like strong magnets in humbuckers and P-90s. But that's just me.

[Antigua]

I haven't tried it with humbucker magnets. I'm sure it would degauss to some extent, but I don't know if it would be by the same amount.

In a Fender style pickup, where the AlNiCo is the core material of the coil, the grade of AlNiCo also has an impact on the inductance and the Q factor. AlNiCo 5 results in a lower inductance and a higher Q factor than the others. In a Gibson humbucker, the coil core is made up of steep poles, so all the magnet is doing is dictating the flux density for the steel pole pieces. The grades of AlNiCo change the inductance of a humbucker also, but only by a few Henries rather than a few hundred.

I'm playing with magnets right now, I charged up two AlNiCo 5 bar magnets. After letting them rest for 10 mins, they measured about 600 Gauss at dead center of the north face. I pressed them together, north on north and south on south, and now they read around 500 Gauss. So they loss of residual flux with the bar magnets was not as great as with AlNiCo 5 pole pieces, only a drop of 15% to 20%, instead of 50%.

[Possum]

There's so much bogus nonsense out there about magnets. Every company has different sounding magnets. There is NO standard alnico recipe that they all use, they all use their own recipes. A5 from one company won't always sound like A5 from another. Neither will they all charge to identical levels. Buy from several companies, listen to them each and organize your magnet pallette and use them for how they sound. A batch of magnets are not all going to be identical, nothing wrong with that, its how it is. American magnets are the absolute worst. Arnold Magnets. Bland, dull, nothing like vintage. You need a DC GAUSSMETER. Alpha Lab makes the best ones. They aren't cheap. I was able to buy a used one for little money, but still have my original from years ago. One problem with them is the ribbon wire always breaks at the shrink tubing from the plug. Finally figured out I could chop the wire off then re-strip both ends and solder them together to put the hall sensor back in business. You also need a real magnet charger. Magnetic Hold is a good company to buy from, Allstar is but high prices. I worked with both of them back around 2007 to reintroduce rough sandcast alnico and were very successful. Chinese are still selling the ones i had them do.