Degauss, or control magnetization strength from the get-go, or use different alloy?

[Chris Turner]

Hey all.


So, on some pickups I'm experimenting with, I'm using 1/4" Alnico 5 magnets that are .720" in length. I'm finding that the magnetization is a bit too strong (causing some warbling)... the magnets are centered on the strings.

I'm sure I'm not the only one to experience this, so what do you all favor as a solution?

1) Stick with Alnico 5 and use weaker neos to magnetize?
2) Degauss after magnetization (but how to do this uniformly?).
3) Use a different alloy?
4) Something else... sorcery, perhaps?

I'd like to stick with the .720" length.

[Antigua]

I'd use AlNiCo 2, 3 or 4, and under-wind the coils slightly in order to achieve the same inductance as you would have with AlNiCo 5. If you have an LCR meter like the DE-5000 you can can ensure that they new AlNiCo 2 poled pickups have the same inductance as the old AlNiCo 5. AlNiCo 2 will bump the inductance up about 5% to 10% higher than had you used AlNiCo 5, due to the difference in permeability of the alloys.

You can degauss AlNiCo 5 by pressing another fully charged AlNiCo 5 pole piece into each one, fighting their urge to repel, and in the process cutting the Br of both by about half, but it's probably much easier to use a weaker alloy from the get go, so that you can just fully charge them and be done with it. I'd only use the tricks if it was a particular pickup that I wanted to alter after the fact. Interestingly, degaussed AlNiCo 5 is very stable, probably more so than fully saturated AlNiCo 2.

I'd guess the warbling is only an issue with the wound strings, the low E and A in particular. Another approach might be to try AlNiCo 2 under the larger wound strings alone, and AlNiCo 5 for the rest.

[Chris Turner]

I'd use AlNiCo 2, 3 or 4, and under-wind the coils slightly in order to achieve the same inductance as you would have with AlNiCo 5. If you have an LCR meter like the DE-5000 you can can ensure that they new AlNiCo 2 poled pickups have the same inductance as the old AlNiCo 5. AlNiCo 2 will bump the inductance up about 5% to 10% higher than had you used AlNiCo 5, due to the difference in permeability of the alloys.

You can degauss AlNiCo 5 by pressing another fully charged AlNiCo 5 pole piece into each one, fighting their urge to repel, and in the process cutting the Br of both by about half, but it's probably much easier to use a weaker alloy from the get go, so that you can just fully charge them and be done with it. I'd only use the tricks if it was a particular pickup that I wanted to alter after the fact. Interestingly, degaussed AlNiCo 5 is very stable, probably more so than fully saturated AlNiCo 2.

I'd guess the warbling is only an issue with the wound strings, the low E and A in particular. Another approach might be to try AlNiCo 2 under the larger wound strings alone, and AlNiCo 5 for the rest.

Hmm... so is a lower Br indicative of higher residual inductance? I ask because in all the charts I've found on properties of Alnico magnets, Alnico 5 has a much higher Br. For example: https://alexkenis.files.wordpress.co...iece-chart.png
.
It seems as though Alnico 6 or 9 would be the closest to 5 as far as Br goes, while having lower strength when fully charged.

[mozz]

Lower the pickup.

[Chris Turner]

Lower the pickup.

Ehhh... that's only so effective.

As it is, the poles of the pickup are 1/4" from the bottom of the strings (open string, nothing fretted). Much lower than that and you start to run into other problems with the sound.

I really think I need to lower the strength of the magnets in this case, as these are humbuckers, with 2 of the 1/4" magnets directly under each string center for each pickup:

[Helmholtz]

Hmm... so is a lower Br indicative of higher residual inductance? I ask because in all the charts I've found on properties of Alnico magnets, Alnico 5 has a much higher Br. For example: https://alexkenis.files.wordpress.co...iece-chart.png
.
It seems as though Alnico 6 or 9 would be the closest to 5 as far as Br goes, while having lower strength when fully charged.

PU inductance depends on core permeability. There is no strict relation between permeability and Br. The table you attached shows permeability values.
The influence of PU magnet permeability on inductance is weak and cannot easily be calculated, so it needs to be measured.
The spectral difference of 5% more inductance could be compensated by 2.5% less turns.

[Chris Turner]

PU inductance depends on core permeability. There is no strict relation between permeability and Br. The table you attached shows permeability values.
The influence of PU magnet permeability on inductance is weak and cannot easily be calculated, so it needs to be measured.
The spectral difference of 5% more inductance could be compensated by 2.5% less turns.

I guess I'm confused... Antigua seemed to be saying that Alnico 2, 3, or 4 would increase the inductance, hence the suggestion of less winds to achieve the same inductance as with Alnico 5...??

[Helmholtz]

I guess I'm confused... Antigua seemed to be saying that Alnico 2, 3, or 4 would increase the inductance, hence the suggestion of less winds to achieve the same inductance as with Alnico 5...??

Antigua is right in saying A2 and A3 (not real A4) would increase inductance compared to A5. So as I mentioned above, a measured increase of inductance of e.g. 5% could be compensated by 2.5% less turns.
The actual increase of inductance with different magnets depends on a number of PU construction details and is hard to predict. But I agree that A2 or A3 would probably cause an increase between 5% and 10%.

[Chris Turner]

Antigua is right in saying A2 and A3 (not real A4) would increase inductance compared to A5. So as I mentioned above, a measured increase of inductance of e.g. 5% could be compensated by 2.5% less turns.
The actual increase of inductance with different magnets depends on a number of PU construction details and is hard to predict. But I agree that A2 or A3 would probably cause an increase between 5% and 10%.

Interesting... so how can this be deduced? Are the charts (like I posted above) that you normally see for the magnet properties no help in determining what the resulting inductance might be? How are you to know that Alnico 2 or 3 would cause an increase in inductance? Is that just from experience and taking real world measurements?

[Helmholtz]

Interesting... so how can this be deduced? Are the charts (like I posted above) that you normally see for the magnet properties no help in determining what the resulting inductance might be? How are you to know that Alnico 2 or 3 would cause an increase in inductance? Is that just from experience and taking real world measurements?

I measured inductance differences between A5 and A2 in strat PUs. A3 is between A5 and A2. But as said, actual percentages will change with PU construction. So you need to measure to be sure. Or just ignore the small shift of the resonant frequency with different alnicos.

A 10% higher inductance has the same effect on resonant frequency as a 10% to 20% longer cable of same type.

[Antigua]

Interesting... so how can this be deduced? Are the charts (like I posted above) that you normally see for the magnet properties no help in determining what the resulting inductance might be? How are you to know that Alnico 2 or 3 would cause an increase in inductance? Is that just from experience and taking real world measurements?

If you make pickups on a regular basis I'd get one of these https://www.amazon.com/5000-Handheld...9079603&sr=8-1 , you set it to test inductance, set the SER/PAR to "SER", and the test frequency "FREQ" to 100Hz and it will will tell you the inductance of the pickup.

I did a test with a Strat pickup, same coil with A2 and A5:
AlNiCo 5
Flux density: _ _ 1000 Gauss
Inductance: _ _ _ 2.016H H @100hz

AlNiCo 2
Flux density: _ _ ~700 Gauss
Inductance: _ _ _ 2.193 H @100hz

The inductance jumped by about 175mH from A5 to A2. So if you want the pickup to sound the same but have a weaker magnetic pull, you just have to make sure it as less turns of wire in order to back the inductance off a bit. 2.5% less turns sounds about right, but you can't really be sure without a meter. Whether the difference is even audible is dependent on other circumstances, but it's just worth knowing up front that the change from A5 to A2/3/4 does in fact push the resonant peak slightly lower.

[kayakerca]

Hey all.


So, on some pickups I'm experimenting with, I'm using 1/4" Alnico 5 magnets that are .720" in length. I'm finding that the magnetization is a bit too strong (causing some warbling)... the magnets are centered on the strings.

I'm sure I'm not the only one to experience this, so what do you all favor as a solution?

1) Stick with Alnico 5 and use weaker neos to magnetize?
2) Degauss after magnetization (but how to do this uniformly?).
3) Use a different alloy?
4) Something else... sorcery, perhaps?

I'd like to stick with the .720" length.

I use spacers between the neo's I use for charging and the rod magnets in the pickup. I find you can really fine tune the gauss level you are looking to achieve and with the same spacer setup for a particular pickup model, you can achieve very consistent results. I charge my pickups with large N42's and use a jig that brings the charging neo's straight in to the pickup being charged and straight back out again, vs passing the pickup between a pair of neo's held in a vice or the like.

When I accidentally overcharge a pickup, I completely degauss the pickup and start over again rather than just take the edge off the gauss level with an opposing magnet.