An in depth text on AlNiCo magnet grades used in guitar pickups

Discussion in 'Pickups' started by Antigua, Dec 9, 2017.

  1. Antigua

    Antigua Senior Member

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    The German group GITEC http://gitec-forum.de/ has recently translated from German to English a chapter on AlNiCo magnets from a larger body of work called "Physics of Electric Guitar", which is still mostly only available in German to date. Here's a link to the PDF https://gitec-forum.de/wp/wp-content/uploads/2017/12/PotEG-4.4.1-Alnico-Magnets.pdf

    This section is rich with information about AlNiCo magnets, including how they're made, why they work the way they do, how they differ from other kinds of metals and permanent magnets, and why AlNiCo can be anistropic or isotropic (oriented). It's rather technical, but it's easy enough to follow, and it serves as a starting point for further googling.

    It's fairly rare to find such in depth information about AlNiCo for free on the Internet, especially since AlNiCo is all but an obsolete type of permanent magnet this day and age, and for it to be geared towards the study of guitar pickups is a double plus, with some interesting pickup history mixed in with the technical details of AlNiCo. There is even an interesting quote from Seth Lover (though keep in mind it was translated to German and then back to English again) in which he claims his preference was for AlNiCo 5, though for technically stated reasons, not tonal reasons.
     
  2. tonybony

    tonybony Senior Member

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    That was a very interesting read, even though a fair chunk flew right over my balding head. It is fun to think that such a simple construct as a pickup has so many different variables that determine the final sound and feel.
     
  3. Leña_Costoso

    Leña_Costoso Senior Member

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    So.... Since alnico 2 magnets are stronger then alnico 3 magnets does this called BS on people who say they use almico 3 for a little boost over alnico 2?
     
  4. Mike_LA

    Mike_LA Silver Supporter

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    Well, maybe the less strong magnet allows for more string movement due to the lessened magnetic field and they can get the pick up closer to the strings?

    Ha ha just kidding . . . .
     
  5. Leña_Costoso

    Leña_Costoso Senior Member

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    Re-re reading that... its all well and good.

    But, as far as tone vs magnet is concerned, its like "kissin yer sister".

    In other words "NUTHIN!"

    It also makes a bit of an issue with "Seth said this and Gibby said that" A bit of techno "nyah-nyah I got ya".

    I do not doubt what they wrote is the truth. I do not doubt they quited Seth correctly (as an old guy when the interview was done) is what he said.

    I also keep a mindful eye out for hyperbole and ingrained group-think lore. That is so much of what we (as a community) see today.
     
    Last edited: Dec 10, 2017
  6. Leña_Costoso

    Leña_Costoso Senior Member

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    Thinking more about this I need some schooling. Seymour Duncan worked with Seth Lover directly. Supposedly the Seth lover pickup buy Seymour Duncan is just the way Seth wanted it and the way Seth originally designed it which was with an alnico 2 magnet. So now these yokels from Germany according Seth Lover as saying no no it's an alnico 5 magnet. I suspect there are multiple levels of BS going on here.
     
  7. CheopisIV

    CheopisIV Copper Slinger MLP Vendor

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    Actually the original humbucker had double pole coils. The screw poles were added for commercial reasons so Duncan didn't build them 'exactly' how Seth wanted them. Looking forward to reading the article when I can get to the computer. Most these type things need to be taken with a grain of salt though. Likely more interesting than factual.
     
  8. Antigua

    Antigua Senior Member

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    The [13] reference beside the Seth Lover quote ties back to this book https://www.amazon.co.uk/Gibson-Steve-Berger/dp/1859093027 . In general, the text is so thorough that it's easy to verify with further searching. This is in contrast to a lot of what Bill Lawrence RIP had posted, where he made claims but didn't really explain how he arrived at many of his conclusions.

    In fact, I saw something in the text that I thought was an error at first:

    "Alnico-VIII, -IX and -XII contain 35% Co. The expensive cobalt enables coercivities up to 130 kA/m, however production is difficult because the material is very brittle. The remanence and specific energy density are smaller than for Alnico-V."

    it's saying AlNiCo 8 has a lower residual flux than AlNiCo 5... but how can that be? We all know AlNiCo 8 is stronger, but with subsequent searching I found out that the higher coercivity also makes a magnet stronger, because this makes it more resistance to self-demagnitization. In other words, it's only stronger because it's not fighting against itself as much. Here's the reference for that https://www.duramag.com/techtalk/alnico-magnets/how-is-alnico-8-different-from-alnico-5/

    Speaking of AlNiCo 8, I don't think I've seen any AlNiCo 8 pole pieces offerred for Fender style single coils, but if there were, due to the higher coercivity, the AlNiCo 8 pole piece would have a more focused magnetic field than the currently used AlNiCo's 2, 3 and 5, because the higher coercivity means more of the magnetic domains within the metal are pointing in the desired direction, and not straying.
     
    Last edited: Dec 10, 2017
  9. LtKojak

    LtKojak Senior Member

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    The magnetic force produced by A8 rods in a SC would make it very difficult to nearly impossible to set-up without getting the dreaded strat-itis. I think that's the main reason why you don't see it advertised everywhere, like A5 rods.
     
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  10. LtKojak

    LtKojak Senior Member

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    I've never seen or heard this before. Would you be so kind to cite your source/s?
     
  11. Leña_Costoso

    Leña_Costoso Senior Member

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    Have not seen it, that I recall, on MLP, but when reading about, researching pickups in general, I see many references to that effect over on the Seymour Duncan forums. Others too, like TDPRI (just comes to mind).

    Admittedly, the SD forum seems a bit kiddie to me, but, I tend to be a sarcastic old curmudgeon with a strong electronics background, as well a background in precision molding, and production manufacturing. I tend to look at things, perhaps a bit more skeptically and analytically then some.

    But I remember various posts, in reference to "juicing up" some pickups that had AlNiCo II magnets, saying that AlNiCo V was "too strong, too harsh" but that AlNiCo III was the perfect upgrade for such and such tone, which invariably required a stronger magnet to boost pickup output. Posts usually go on to berate Duncan for not using AlNiCo III in the first place, etc etc.

    I take all of this in stride, and try not to follow the group-think, but have a more open mind. If you try it and like it, and it works for you, then by all means... go for it.

    Group-think is a powerful marketing lever. Quite some years ago, I was in Guitar Center in Hallendale, Florida. Pickin' up some strings for my Adamas, the sales guy asked what amp I use with it. Mostly acoustic, but if I need to amplifiy, I use my Twin Reverb. It was like I told him I was flying a garbage truck to the moon. He said playing an acoustic guitar through an amp made for standard electrics was going to "tear up" the amp. Why? Something to do with the speakers. So it just tears up the speakers, not the amp? No the whole amp will be fried. Group-think in action.

    BTW, the Twin Reverb, with EV Force-12s (the poor man's JBL) sounded great with my Adamas, which has its own 5 band EQ to compensate for the "Fender scoop". Never any complaints at least. And I have no idea what magnets EV used in them, nor do I care.
     
    Last edited: Dec 10, 2017
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  12. ARandall

    ARandall Senior Member

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    Alnico 4 has been the typical recommendation in those cases on the Duncan forum for the maybe 10 years or so. It certainly was already when I joined close on 8 years ago.
    Both the Lt and I are on that forum and I cannot remember a single time where A3 has been used in that context.

    It is often recommended for neck pickups however where less boominess is wanted but you still want some of the mids and rolled treble of A2. But this is not at all the same direction.
     
    Last edited: Dec 11, 2017
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  13. freefrog

    freefrog Senior Member

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    Believe it or not but I’ve already seen such a thing happening. Recipe to follow:

    -set a parametric EQ in order to create a drastic mid scoop (-20dB, Q=1, center frequency = 1khz);
    -put it in the loop of a tube amp with an undersized OT;
    -play. You’ll have to bump the output level since the mid scooped EQing will have generated a really low volume;
    -use a guitar with the strongest humbuckers. At first, you might find delightful to hear it sounding so crisp and clear, almost acoustic.

    What doesn’t appear is that the EQ is now sending way too much voltage to the power section, in a high frequency range that guitar loudspeakers can’t reproduce.

    So, keep playing and the output transformer will fry, unless the amp is fitted with “flyback diodes”… The tubes might die too.

    Such an accident if of course way less probable with a Twin, whose Output Transformer has been designed to be ultra linear and includes incredibly big “irons” (hence the weight of these monsters).

    Now, if memory serves me, most Twin’s don’t feature flyback diodes so it seems theoretically not impossible to “tear” their OT with too high voltages in the extreme high range – like those potentially sent by a preamplified acoustic guitar.

    END OFF THE OT (= OFF TOPIC and not “output transformer”- LOL). :)


    Such posts might have referred to fatter mids due to A3 causing a higher inductance, while the idea of “too harsh” A5 mags can easily be correlated to their stronger mag field paired with a weaker inductance / higher pitched resonant frequency of the host pickup.

    IOW, even if such posts are worded in a necessarily not precise metaphorical way, there’s potentially “something” behind, IMHO.

    IOW: there's no smoke without fire. :)

    I’ve really not enough free time to develop the experimental data that I've archived about AlNiCo alloys (and no desire at all to discuss such things in a potentially controversial context) but I find it to be a complex subject, knowing the vast diversity of magnets in empirical reality (even in a supposedly same alloy), the variations in their interactions with other pickups parts and the results that some tests can give, as soon as they aren’t limited to Rz, flux density or inductance measurements considered separately or exclusively.
     
    Last edited: Dec 11, 2017
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  14. Antigua

    Antigua Senior Member

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    AlNiCo 2, 3 and 4 have very similar permeability values, and so they make for virtually identical inductances for a given pickup. AlNiCo 5 has a lower permeability than 2, 3 or 4. I'm not sure about the permeability of 8, but I imagine the higher coercivity means the permeability is going to be substantially lower that 5.
     
    Last edited: Dec 11, 2017
  15. freefrog

    freefrog Senior Member

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    Sorry to quote impudently myself, dear online community: as I always visit hastily Internet forums before or after busy days, I often feel the need to edit my answers later or to treat them as “to be continued” (even if in “dotted lines”).

    Here are a few words that I couldn’t add to the last post, by lack of time.


    When I slide two mags of the same dimensions in a same PAF clone, its inductance reaches 4.4H @ 120hz with A3 Vs 4.1H with A5.

    It’s not that negligible, knowing that 0.3H is roughly the difference between a Fender CS69 and a mid or neck Fat 50’s.

    Then, when I measure the A3 and A5 bars with our lab Teslameter and notice in the A3 60% of the charge exhibited by the A5 after the same time in a magnetizer, I’m not surprised to see the pickup with A3 as fatter and softer sounding than with the A5 on frequency charts summing up played tracks…

    But of course, such data are only a part of the pic.


    "To be continued" (or not)... :)
     
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  16. Antigua

    Antigua Senior Member

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    Keep in mind that the higher the inductance, the smaller the difference becomes. Assume 470pF capacitance:

    2.2H = 4.95 kHz
    2.5H = 4.64 kHz
    ... difference of 310Hz

    4.1H = 3.63 kHz
    4.4H = 3.50 kHz
    ... difference of 130Hz

    That being said, 130Hz is still a difference that can be heard, though it's probably subtle. When you get into JB's and P-90's you see inductances around 8 to 9 henries, and one henry doesn't make nearly difference when you get way up there.

    Another interesting aspect of permeability is that it will also make the pickup produce more voltage by itself, aside from the increase in inductance, and that's because the lower magnetic reluctance also causes the AlNiCo magnet to see a greater magnetic change in response to the moving guitar string. Therefore, even though AlNiCo 2, 3 and 4 have a lower residual flux than AlNiCo 5, to where it can be said that they do not charge the guitar string as well, it can also be said that they're more receptive of the magnetic change caused by the moving guitar string. This lower magnetic reluctance allows AlNiCo 2, 3, and 4 to win back some voltage production that they lose due to the relative lack of residual flux. It's especially noticeable with Strat / Tele pickups where you see rather little difference in voltage output between AlNiCo 5 pole pieces compared to AlNiCo 2 or 3 pole pieces, despite the fact that the AlNiCo 5 pole pieces hold nearly twice as much residual flux. AlNiCo 8 presumably goes even further than AlNiCo 5, with even more magnetic strength, and still less inductance, getting ever closer to ceramic.
     
    Last edited: Dec 11, 2017
  17. freefrog

    freefrog Senior Member

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    … & to avoid comparisons between apples & oranges: 4.4H is also the inductance mentioned by Bill Lawrence for a typical P.A.F. … while 4.1H is a value that I’ve measured more than once on T-Tops – models making NO difference at all, as anyone knows. LOL.

    More seriously: as I said above, “such data are only a part of the pic”. I see inductance and “Gauss” levels as basic specs, providing a rough idea or the reasons why A3 gives a tad more mid and smoother high than A5 (with tighter bass than A2)...

    But it’s just a rough idea: one of my friends has designed a (covered) PAF sized humbucker measuring a whooping 12H of inductance and whose sound is still clearer than the tone of current Gibson models, with an inductance 1.5 to 3 times lower… So, granted, "inductivity" alone doesn't reveal the whole pic.

    I’ve my own reasons to keep unpublished some testing procedures & experimental data about magnets but I can share at least a conclusion: the differences underlined above can be seen in the dynamic response of a pickup, during lab tests… & It helps to understand why people “hear” differently various AlNiCo’s. :)
     
    Last edited: Dec 12, 2017
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  18. Antigua

    Antigua Senior Member

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    I've always heard the PAF variability was too great to nail down an average inductance, but if Bill Lawrence worked for Gibson, I suppose he'd be somewhat authoritative. Since Gibson was using a mechanical winder, I'd expect their pickups to be more consistent than Fender, who were hand guiding their pickups. I measured 4.8H @ 120Hz for my late make 57 Classic.

    The only way you can get an inductance that high, without using added external series inductance, and without incurring a correspondingly high parasitic capacitance, would be to use a ferrite core. That's incidentally how the Bill Lawrence Q filter works, which is really nothing more than an high inductance, low loss inductor. DiMarzio also puts small ferrite buttons in some of their PAF type bobbins to increase the output slightly. It's an open question as to why ferrite cores are not a more common feature in guitar pickups.

    Outside of a profit motive, what good reasons are there not to share?
     
    Last edited: Dec 12, 2017
  19. Antigua

    Antigua Senior Member

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    I found an interesting table that puts a handful of magnet metrics in one place, for among others, AlNiCo 2, 5, 8, ceramic:

    [​IMG]

    Notice that ceramic and AlNiCo 8 are similar in that they have lower residual inductaions than AlNiCo 5, but higher coercive force, so it's from that higher coercive force that they derive their higher strength in situ.
     
  20. freefrog

    freefrog Senior Member

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    Your question creates its own answer.

    The first version was asking: “What good reasons are there not to share?”

    Then you have edited it to add a restriction: “Outside of a profit motive, what good reasons are there not to share?”

    Something is clearly missing here if you want people to share things with you. Hear the frog:

     
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