Magnet mixtures?

[cnb77]

If I have uncharged alnico pole pieces and I just stick neo disc magnets to the bottom to provide the magnetism, what will it sound like?

[David Schwab]

If I have uncharged alnico pole pieces and I just stick neo disc magnets to the bottom to provide the magnetism, what will it sound like?

Well it wont sound like Alnico, but it will probably sound different from steel poles.

DiMarzio does something similar with the Ultra Jazz bass pickups. They use alnico poles charged with ceramic magnets.

Give it a try and see what you get.

[cnb77]

That I will! I'll report back when I'm finally done

[Fluoroscope 5000]

Whatever metal used in the poles (core) will have a limit to the amount of power it can accept before it becomes saturated. Unless you use very thin Nd magnets that don't exceed the capacity of the AlNiCo, that will likely happen. It will decrease inductance and maybe cause phase cancellations from eddy currents. Not sure about that last affect.

[cnb77]

Would alnico 5 be more or less easily saturated than steel poles? They are pretty small disc magnets, and I have a few sizes so it shouldn't be a huge problem

[Fluoroscope 5000]

Don't know what saturates sooner, but the AlNiCo should become permanently magnetized. There is no point in keeping the Nd magnets on them. Even the lowest Gauss 1/32" thick N35 magnet's have much higher Guass than is recommended for a pickup, and will cause string modulation unless some measures are taken to reduce the power above the pickup surface. You could use some kind of spacers, but there are other methods I don't know about.

[salvarsan]

Add Nd magnets to *all* the Alnico rods, otherwise the Nd magnets might partially demagnetize the adjacent Alnico rods because of their much lower coercivity.

[Fluoroscope 5000]

Forgot to ad that the Nd magnets will likely saturate the AlNiCo, lowering inductance and causing phase cancellations due to eddy currents. Be interesting to compare identical pickups with and without the Nd magnets.

[David Schwab]

Don't know what saturates sooner, but the AlNiCo should become permanently magnetized. There is no point in keeping the Nd magnets on them. Even the lowest Gauss 1/32" thick N35 magnet's have much higher Guass than is recommended for a pickup, and will cause string modulation unless some measures are taken to reduce the power above the pickup surface. You could use some kind of spacers, but there are other methods I don't know about.

I use N42 and even some N52 grade neos in pickups. Unless you are using neo rod magnets as poles, you wont get any string pull or modulation. I'm using these magnets in direct contact with steel blades. When measured at the top of the blade,it reads less than you will find on an alnico pole. So while a Jazz bass pickup might read 700G, mine read about 300G. The neos themselves are listed at 4871 Gauss for the N42s. I don't think the steel is getting saturated at all.

[Mike Sulzer]

Don't know what saturates sooner, but the AlNiCo should become permanently magnetized. There is no point in keeping the Nd magnets on them. Even the lowest Gauss 1/32" thick N35 magnet's have much higher Guass than is recommended for a pickup, and will cause string modulation unless some measures are taken to reduce the power above the pickup surface. You could use some kind of spacers, but there are other methods I don't know about.

Small Neos on the bottom of steel pole pieces do not make the field too strong. You just have to experiment to get the correct strength. I do not see why this would be a problem with alnico rods either. The permeability of alnico is not that high, not nearly as high as steel. If a small neo would fully and permanently magnetize a rod, then most people are using much stronger fields than necessary in their set ups.

[Fluoroscope 5000]

Even 1/32" thick Nd35 can have 2x+ the Gauss that a 0.71" AlNiCo V rod can hold. I don't know how much it takes to magnetize such a rod, but it's likely to be enough to do something. It is a fact that saturating the core will decrease inductance, as David's 300G reading on the steel blades may be an indication of. You might actually get higher Gauss from the blades if you used lower Gauss magnets that don't exceed the (permeability?) of the blades. I'm not sure how all that works, but I know it is an issue. Furthermore, I would think the field might form ripples around the core from too much power being forced through the material. Speculation on my part, but makes sense. If true, those ripples (eddy currents) will cause some types of phase cancellations.

[Mike Sulzer]

Even 1/32" thick Nd35 can have 2x+ the Gauss that a 0.71" AlNiCo V rod can hold.

I do not know exactly what that statement means, but if you put such thin Neos on a coil with steel pole pieces, the inductance does not change a lot, and so you are not saturating it.

I don't know how much it takes to magnetize such a rod, but it's likely to be enough to do something.

If you were able to satruate it, that would pretty much do it!

It is a fact that saturating the core will decrease inductance, as David's 300G reading on the steel blades may be an indication of. You might actually get higher Gauss from the blades if you used lower Gauss magnets that don't exceed the (permeability?) of the blades. I'm not sure how all that works, but I know it is an issue.

You are right about one thing. But if you saturate the steel blade, you have the maximum magnetization it can support, and so you get the highest reading above it. Using weaker magnets will not give a stronger field at the top of the blade.

Furthermore, I would think the field might form ripples around the core from too much power being forced through the material. Speculation on my part, but makes sense. If true, those ripples (eddy currents) will cause some types of phase cancellations.

Putting a material in a static magnetic field does not force power through the material. A ferromagnetic material in a magnetic field under goes changes that are simple to understand in principle, but hard to compute exactly:

Atomic current loops are small magnetic dipoles, usually grouped together in domains with all of them pointing in the same direction. The external field causes domains to flip, lining more of them up. Domains in a high permeability material are easier to flip than in a low permeability material. A permanent magnet is a material in which the domains remain flipped when the applied field is removed. Very strong magnets (such as Neo) have low permeability since nearly all the domains are already lined up and it is quite difficult to flip more.

[David Schwab]

But if you saturate the steel blade, you have the maximum magnetization it can support, and so you get the highest reading above it. Using weaker magnets will not give a stronger field at the top of the blade.

This is exactly my thoughts on it. You motivated me to do a test. So I took a pair of blades I use, and tried three different magnets and took reading touching the top of the blade. When the pickups are in the cover the strength is a bit less.

Alnico:

Humbucker size A5

Magnet = 452G
At blade = 224G

Ceramic 8:

3.33"L x .196"W x .500"T

Magnet = 1271G
At Blade = 502G

N42 Neodymium:

1"L x .500"W x .250"T

Magnet = out of range (>1500)
At blade = 704G

The blades were 3"L x .125W X .750"T and made from 1010 carbon steel. I put one on each side of the magnet and read the north pole on each one.

Is the blade with the neo saturated? I wonder if the reading would be higher otherwise?

[Mike Sulzer]

Is the blade with the neo saturated? I wonder if the reading would be higher otherwise?

It might be saturated near the magnet, but not a bit further away. These are short, open pole pieces.

Notice that the ratio, Bmagnet to Bblade is not quite the same for the alnico and ceramic. This might mean that even with the ceramic, the steel right at the magnet could be saturated, or at least on a portion of the B-H curve with decreasing slope if not completely saturated.

[Joe Gwinn]

What's missing is the difference between field intensity (in Gauss or Tesla) and total flux (in Webers). The Neos (like all permanent magnets) generate total flux in proportion to their volume. This flux then spreads out through the iron and air, and the field intensity is set by the flux per unit area of the iron poles. (Well, I'm simplifying, as the iron can saturate and not all the neo flux will go through the iron, et cet, but this rule is pretty good.)

Weber (unit) - Wikipedia, the free encyclopedia