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Magnet Structures

Discussion in 'Pickups & Electronics [BG]' started by Bayha, Nov 22, 2010.


  1. Bayha

    Bayha

    May 2, 2005
    Tehachapi
    As a fun project, out of curiosity, I'm starting to look into building a pickup. There is one part I'm still confused on though; the way the magnets are placed. I've seen where there is a large magnet on the bottom with non magnetic pole pieces directing the flux towards the string and also where the pole pieces are the magnets. What are the sonic differences in these two methods? Thanks in advance.
     
  2. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Pole pieces are always magnetic, but not always magnets.

    Early pickups used cobalt steel magnets, like the old Rickenbacker/Electro horseshoe and the Gibson "Charlie Christian" pickup. But they aren't very good magnets.

    The next magnet invented was the alnico. Fender used alnico rods as poles. Gibson used steel screws as poles so they could be adjustable. So as an example the P-90 had steel screw poles and two alnico magnets under them.

    Then ceramic magnets were introduced and some makers used them, such as DeArmond/Rowe, Rickenbacker and Burns. They can be used with or without steel poles, but generally steel poles are used.

    As far as why and when to use each type depends on what tone you are going for.
     
  3. Bayha

    Bayha

    May 2, 2005
    Tehachapi
    Thanks for the quick response. I have a book by Mario Milan about pickups. It's not bad, but only a small portion has information about construction. I've also done some internet searches, but get frustrated very easily because so much unrelated bull**** comes up. Can you recommend any resources for info on pickup construction? Thanks again.
     
  4. wcriley

    wcriley

    Apr 5, 2010
    Western PA
  5. Stealth

    Stealth

    Feb 5, 2008
    Zagreb, Croatia
    It IS a forum full of guys who build pickups. The link is live.
     
  6. wcriley

    wcriley

    Apr 5, 2010
    Western PA
    Yeah, it works today.
    I couldn't get it to open last night after I posted.
    Dang interweb gremlins musta' got me!
     
  7. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    The p90 bar magnet style pickup has a wide 'aperture' magnetic field. Wide enough that not 100% of the windings are always within the field. Another characteristic is that there is more string length within the field. This results in the softer bottom, more enhanced mid range, 'bark' associated with the design. The pole piece as magnet design results in a narrower aperture field. Less string length and a fully engaged coil. Sonically the results are quite striking with a bass. My extreme preference is for the pole piece as magnet with one exception... The Dark Star ... Note sure how that one pulled it off but ... Even with the huge honkin' magnet and I assume mild steel poles, it does have the single coil edge and clarity working over time.
     
  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    by the same token, a pickup with the magnet on the bottom and steel slugs will typically be louder than one with the same amount of wire wrapped around actual alnico magnet poles. it's a more "efficient" magnet structure, which is why leo went to it with his G&L instruments.

    many cheap import pickups are louder than their boutique alnico replacements for this reason. (not to say that the good ones don't sound better, because they usually do.)
     
  9. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    Places like StuMac sell pickup kits so you can get started.

    One other thing: Alnico, with its iron content, whether as a humbucker or P-90 bar with separate pole pieces, or as actual magnetic polepieces themselves, will affect the inductance of the pickup, which affects tone, generally with more mids and a more "complex" high end. Ceramic does not interact the same way, so there is less impedance to a pickup. This means generally not only are the cheap pickups louder for the reasons above, but they have more wire on them so the coil does not "saturate" from too strong a magnet and sound harsh. But unless it's wound and assembled properly, like the good reputable makers do, a ceramic magnet pickup can sound "one dimensional."
     

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