Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

P90 Magnets

Discussion in 'Just Pickups' started by ftbtx, Nov 3, 2017.

  1. ftbtx

    ftbtx Tele-Holic Silver Supporter

    Hello,
    I'm going to swap the baseplate and cover on a P90 and was thinking about swapping the magents while I'm at it. It'll be in the bridge of an LP Jr and I'm going for that Leslie West kind of sound.

    I was thinking about an A2/Rough Cast A5 pair. Any other ideas?
     

  2. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    They're pricey, but go to Throbak's website and check out their options. They supposedly (and are the only one's doing it) recreated the Alnico make up of vintage magnets. I have a set of A4 long, rough cast from them. I really like them.
     
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  3. rigatele

    rigatele Tele-Holic

    755
    Apr 20, 2014
    Ontario
    Magnet swaps are over rated.
     
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  4. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    A mixed par of A2/A5 rough cast? I have no experience with that, but from the little bit that I understand about this stuff I'd reckon it would sound good.
     
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  5. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    I can't necessarily disagree with you, though I've done it. The changes are there, but they are subtle.
     

  6. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    Changing the magnets is very much like adjusting the height of the pickup, but people choose not to think about it in those terms.
     
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  7. Asmith

    Asmith Friend of Leo's Ad Free Member

    Age:
    21
    Nov 27, 2014
    Morley, England
    Do you know what magnets are currently in the pickup? Also, I wouldn't read into too much into the differences between polished and rough cast magnets, a magnet is a magnet and the only differences you'll hear are the differences in the field strength.
     
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  8. jvin248

    jvin248 Friend of Leo's

    Apr 18, 2014
    Near Detroit, MI
    .

    Can't say for bar magnets, but the shape of the tips on Strat-style magnets can make a difference: "pointy" or "flat" changes how acute the magnetic flux lines leave the end of the pole piece, and they sounded quite a bit different when I tested them. I have imagined that the bar magnets that are ground with sharp square corners behave differently than the rounded raw sand-cast ones.

    .
     
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  9. BorderRadio

    BorderRadio Poster Extraordinaire Silver Supporter

    Apr 2, 2014
    Phoenix, AZ
    Then factor in the physical limitations of a given pickup design. Only so close one can get to the strings before string clicks (*glaring at Filtertrons*).
     
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  10. rigatele

    rigatele Tele-Holic

    755
    Apr 20, 2014
    Ontario
    That's probably because the Filtertrons have more distance from coil top to string. The tall protruding pole screws create that. It's actually a design flaw. It stems from a misconception of output as being relative to static magnetic circuit field strength vs. output relative to dynamic string field strength in the pickup geometry.

    The early designers observed that the output increases in proportion to the field strength at the poles and made efforts to increase it. However the output is also inversely proportional to the distance between the coil and string. If a coil is too tall, the windings that are furthest away from the strings have a lesser induced signal than the windings up closest to the string. The closer the strings are, the greater the difference. Horizontally, the outer windings of the coil also have a diminished signal, so flattening the coil has no benefit beyond a point. Since the best signal is to be had close to the string, the best coil cross section would be almost square. The best position for the pole would be as close to the top of the coil, because it places the coil at the optimum position for the chosen pickup height that is dictated by the pole top position. The pickup height is a trade off between playability if close, and output volume if distant. Experiments have also shown some tonal changes due to magnet pull, which also influence the technician/player's choice of height.
     
    Last edited: Nov 3, 2017

  11. BorderRadio

    BorderRadio Poster Extraordinaire Silver Supporter

    Apr 2, 2014
    Phoenix, AZ
    I don't consider it a flaw, just a quirk. With 11s it doesn't click as much due to tension. When I had 10s and a TVJ Classic+ it was mildly annoying. If the bar was changed to A8 how would characteristics change compared to a A5 at max practical height?
     

  12. rigatele

    rigatele Tele-Holic

    755
    Apr 20, 2014
    Ontario
    I reserve an opinion on that as I haven't
    Not quite. Different magnet alloys have different permeability, which manifests itself in the pickup as a change in inductance. That can measurably change the frequency response, hence the tone. However the differences are subtle.
     
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  13. rigatele

    rigatele Tele-Holic

    755
    Apr 20, 2014
    Ontario
    The way to figure it out - if the Gauss is higher, the output will be higher. If the permeability is lower, it will raise the resonant frequency and make it slightly brighter sounding.
     
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  14. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    Another way to look at it, then, is that a stronger magnet give you more choice in terms of distance.

    Another caveat is that the magnet also changes the inductance, a lot in a Fender style single coil, and a little in a humbucker/P-90 context, but when we talk about magnet swaps, it's only every in a humbucker/P-90 context. I forget the exact amount it altered the inductance, but then again this is the sort of think that also readily changes when you switch out guitar cables, or an assortment of true bypass pedals.

    The permeability of AlNiCo 2 is a little higher than AlNiCo 5, so if you have two pickups that are 6k, exactly 8000 turns, and one has AlNiCo 2 and the other AlNiCo 5, the one with AlNiCo 2 will sound like the one with AlNiCo 5, if the AlNiCo 5 were lowered, and had a few dozen or so additional turns added to its coil.
     
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  15. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    You lost me at "quite a bit different". I think it's suspect that it would sound any different, because when you talk about the result of varied aperture width between, say 5mm and 3mm, or flat versus chamfered, the physical widths of the harmonics you're increasing or decreasing sensitivity to would be of a very high frequency. With PAFs / Filter'trons being about 18mm apart pole to pole, you're nearing the edge of audibility, and with single coils sized humbuckers, even thinner still, its more or less an inaudible difference between two blades and single row of pole pieces.

    Another possibility is that the the pointy pole piece pulls on the string differently than a broad pole piece, but that's getting really out there. I don't know for certain it would sound no different, but I'm fairly sure it wouldn't sound a lot different. In order to adequately test something like this you'd need pristine test conditions that go far beyond your everyday pickup swap A/B test.
     

  16. BorderRadio

    BorderRadio Poster Extraordinaire Silver Supporter

    Apr 2, 2014
    Phoenix, AZ
    Yeah, this is more or less what I mean. I know when I was experimenting with a magnet swap in a cheap ceramic Epi Dogear P-90, I had limited choices for height adjustment with shims. I replaced the ceramic bars with AlNiCo (forgot which types) but the height variable had to stay pretty much the same, which was whatever shim got me closest to the strings without bumping into them. I still had clicks from my pick scraping the pickup top when I dug in.

    So maybe I could of mounted the ceramic pickup without the shims and get the ‘alnico sound’ lol, but then I’d have to live with the social stigma that comes with using cheap ceramic pickups :)
     
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  17. Asmith

    Asmith Friend of Leo's Ad Free Member

    Age:
    21
    Nov 27, 2014
    Morley, England
    Inductance is effected by the magnetic permeability of the core material and the bar magnets are not in the core of the coil so they're affect on inductance is minimal. Also I doubt there is a massive difference in the permeability of different alnico magnets (although I haven't checked so) if I'm wrong about that me
     
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  18. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    Permeable metal all around the coil effects the inductance, because it is all within the magnetic field of the coil. That's what transformers, and sometimes inductors, have metal cores that go all the away around the coil. It's just that the core is where the flux is most concentrated, so the contribution of the permeable material is disproportionately high in that location.

    AlNiCo 2, 3 and 4 are all near identical with respect to permeability, but AlNiCo 5's is lower. None of the AlNiCo's permeability is anywhere close to that of electrical steel, though. This measurement I made a year or two ago demonstrates this.You kind of need a magnifying glass to read it, but the higher peak frequency means lower inductance, hence lower permeability.

    [​IMG]
     
    Last edited: Nov 4, 2017
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  19. rigatele

    rigatele Tele-Holic

    755
    Apr 20, 2014
    Ontario
    The
    You're right. The difference is in small fractional dB's. I've seen strong evidence that some things that people claim to hear, can not be supported by science. But I don't often debate such perceptual questions these days because I barely have time to do the research that I do, let alone that. If you go to journal articles on human hearing, you are in for a shock regarding how poor our physical hearing mechanism actually is. The psycho-perceptual layer that connects it to our brain, fools us into thinking it is a lot better than it really is.
     
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  20. deytookerjaabs

    deytookerjaabs Friend of Leo's

    Jun 5, 2015
    Nashville

    That's nice, but improving the function of the ear across pitch/timbre/harmony to near perfection is provable scientific fact. Training is everything. Play a piano concerto to a music school freshman, then play it to the same guy when he's getting his PHD in composition. Can you pick out recorded voices of 50 of your most known family/acquaintances? Do you know how long that would take you, if say, you tried it with 50 random mandarin speakers? Our acute hearing abilities are as equally impressive as they are flawed.
     
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