Dumb question: Easy magnet identification?

[Mark Norwine]

After years of fiddling with guitars, I have accumulated quite a few pickups (almost all humbuckers), along with pickup parts & loose magnets...you name it.

I have no idea what all I have, what's stock, what's been fiddled with, etc.

Regarding coils, I can measure the resistance.....I can measure the inductance. That's simple.

But how can I determine if the bar magnet is A2, A3, A4, A5, etc.? Either in the pickup or as a loose magnet? Is there a simple method of verifying composition?

Dumb question...I know. But I've got all these magnets & have no idea what's what.

Thanks,

mn

[madialex]

Buy a Gauss Meter and look up what all the different mag types should read and you should get pretty close to what they all should be, unless some are very weak or such

[LtKojak]

After years of fiddling with guitars, I have accumulated quite a few pickups (almost all humbuckers), along with pickup parts & loose magnets...you name it.

I have no idea what all I have, what's stock, what's been fiddled with, etc.

Regarding coils, I can measure the resistance.....I can measure the inductance. That's simple.

But how can I determine if the bar magnet is A2, A3, A4, A5, etc.? Either in the pickup or as a loose magnet? Is there a simple method of verifying composition?

Dumb question...I know. But I've got all these magnets & have no idea what's what.

Thanks,

mn

I'm in a very similar position as yours, but I've made my homework and I've found that almost all of them had ceramic magnets, which I hate the sound they produce in a humbucking p'up.

But if you've already took'em apart and stored the magnet bars without taking notes, there's no way to physically recognise'em apart that I know of.

[belwar]

Buy a Gauss Meter and look up what all the different mag types should read and you should get pretty close to what they all should be, unless some are very weak or such

Thats pretty much the only way I can think of. You have to charge the magnets to thier fullest, then measure them.. There is a chart floating around of the relative strength of each.. ie. A3 might be the weakest, which A8 might be the strongest (or something like that).

[Mark Norwine]

Buy a Gauss Meter...

Any suggestions for a (hopefully) inexpensive, suitable meter? Is there a particular unit that "everyone" uses?

[Possum]

....

This really isn't going to work, a gaussmeter can't tell the difference between alnico 2 and 4, and typicallly the magnets aren't fully charged so you may have a bunch of magnets with all about the same charge and can be different alnicos. Worse yet, every manufacturer's alnicos are different, I have some alnico 2 that will hold nearly a 700 gauss charge like alnico 5 will. You can get pretty close using an Extech LCR meter but even that can't distinguish between some alnicos that are close in metals content. Best thing is to look up your pickups on the manufacturer's website and find out what alnico they used....

[Diablo]

Different magnet composition will have different density and different electrical resistivity. See the following tables:

http://www.advancedmagnetsource.com/...-alnicomat.pdf

However, what really matters is the strength of the magnet (gauss), not what it is made from, unless you have plans to magnetize them yourself.

[belwar]

This really isn't going to work, a gaussmeter can't tell the difference between alnico 2 and 4, and typicallly the magnets aren't fully charged so you may have a bunch of magnets with all about the same charge and can be different alnicos. Worse yet, every manufacturer's alnicos are different, I have some alnico 2 that will hold nearly a 700 gauss charge like alnico 5 will. You can get pretty close using an Extech LCR meter but even that can't distinguish between some alnicos that are close in metals content. Best thing is to look up your pickups on the manufacturer's website and find out what alnico they used....

Right, but if you charge them to full strength BEFORE measuring them then you can get a better idea of what is what ... Not very accurate, but close enough for most I would imagine.

[belwar]

Any suggestions for a (hopefully) inexpensive, suitable meter? Is there a particular unit that "everyone" uses?

http://www.carlsenmelton.com/gm200a/...FQ7aDAodfz8oBw

[salvarsan]

Different magnet composition will have different density and different electrical resistivity. See the following tables:

http://www.advancedmagnetsource.com/...-alnicomat.pdf

You will be measuring densities to an accuracy of 1 in 70 or ~1.5%.
The bar magnet resistances are below 1 ohm.
This means careful technique and a milliohm meter.

However, what really matters is the strength of the magnet (gauss), not what it is made from, unless you have plans to magnetize them yourself.

If the magnet is partially degaussed, its more difficult to make a useful comparison. The magnet permeability changes with its magnetization so you can't even test it as an inductor core.

-drh

[Possum]

..

That chart says "typical" composition, its like saying all milk is the same. Its VERY important what alnico is made of because each manufacturer uses its own recipe and each will vary in guass capability and tone in a pickup. Sure you can charge them full strength, about all you'll really be able to do, maybe, is pick put alnico 5 from the rest. Alnico 2 and 4 hold similar charges, alnico 3 you may be able to pick out because typically its the weakest, but I have some alnico 3 that will hold a charge near 2, and 4 levels. If you have no idea what is what and they are all in a pile, charge them all full strength but you'll need to do this in a real charger because neo magnet charging isn't a steady consistent method. Then classify them by charge strength using a digital gaussmeter. Thats about as far as you can get; put them in the pickup and listen, because of the different chemical compositions you may be able to pick out which is which, but you may also get that completely wrong :-)

[cryptozoo]

Hopefully I'm not speaking out of turn here -- I'm no expert, but one thing I've found which is useful to me in discerning AlNiCo5s from 2s and 3s is to do a compass test or screwdriver test. I use a compass to tell me the polarity of the mags, and when messing with old 50s mags, this method works for me because I knew which was an A5. Once that had been established, as you'd imagine, old mags that are A2s or close don't pull the compass nearly as hard, and they don't adhere to the screwdriver as fiercly, either. Granted, I may wind up with an A3 and think it's an A2, but typically I'm trying to seperate A5s from other magnets, so this method works for me.

[Possum]

...

I'm sorry but that method is full of holes too :-) Gibson often and maybe always bought manufacturer's "reject" magnets no one else wanted, for a cheaper price. Gibson never charged their own magnets and they were stored thrown together in drawers or boxes. So every magnet of the same alnico would not have the same charge. Vintage magnets may have been around magnetic AC fields that would lower the guass levels over time. So, you could have an alnico 3 that had a high charge to begin with and wasn't used much that will have a hot charge, and an alnico 5 that never had a hot charge and had been degaussed partially over time in exposure elements. So in that scenario your method would identifiy the alnico 3 as being alnico 5. It just doesn't work. Even now when you buy new bucker magnets they come shipped in a brick, they are magnetized en masse and never have the same charge from magnet to magnet. the only true way to identify alnico beyond doubt is to vaporize it in a spectrum analysis test.....

[cryptozoo]

Possum, my method is definitely full of holes, and I'd be the first to admit it. I guess the point I was trying to make is that for my purposes, which might be seperating stronger mags that I'd like to try in a bridge from weaker mags I'd like to try in the neck, it's worked OK. I've been fairly happy with the results, and I can certainly hear a difference between two magnets of a different type. Unfortunately, you're right, it is far from a scientific way to accurately ID the mags.

[Possum]

...

Yeah all you can do is use your ears really. I degauss my PAF magnets for a vintage feel, you actually get more useable tone in my opinion, a fully charged magnet in a bucker gives you this big blast of volume at the very end of the pot range, having a weaker magnet evens it out a little better, plus you can turn up louder and actually have some tone plus volume, whereas a fully charged magnet just mushes everything out at high volumes....probably why DiMarzio has that "air gap" thing he patented...