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Magnetic interaction between pickups

Discussion in 'Pickups & Electronics [BG]' started by 62bass, Dec 21, 2006.


  1. 62bass

    62bass

    Apr 3, 2005
    I have a question I hope someone who has experience with this can answer. Has anyone mounted a J style pickup very close beside a large MM style humbucking pickup? Was there any degradation in the sound of either pickup because of possible magnetic interaction between the two pickups?

    I was thinking of adding a J style pickup in the standard neck position on a bass that is equipped with a MM style humbucker in the standard MM position. I measured and doing so would put the J pickup about 1 inch from the MM pickup. This would not involve blending the pickups. I'd have a switch so it would be one or the other using the existing passive volume and tone controls. I'm just concerned that there might be some magnetic leakage that might degrade the sound of either pickup.

    I know there have been basses with some pickups stuck on very close together, like Bootsy Collins basses and the Fender Urge, but I don't care for the sound of those basses. I just want to be able to switch to the sound of a soloed J pickup in the neck position and have it sound as good as possible, without also degrading the sound of the existing pickup.

    If anyone has any thoughts on this, I'd like to hear them, before I get the router out and start hacking.
     
  2. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    FWIW:

    Seems altering the magnetic field alters the tone. How I don’t know. Personally I can’t accurately predict sound so it’s trial and error. But you have two banks of 44 slug mags in your MM almost 1/2 inch apart so it’s not the distance it’s the relationship of them. I held an Ray and Marcus Miller J side by side and I could feel the mag fields start to interact at about 1 inch, how far out distinguishable tone is effected I have no way of knowing. I have set Bart J’s side by side and basically got a Bart MM tone when wired in accord. At any rate, you’d want to set the pups so they’re pulling toward each other not pushing away (opposite poles aligned).

    An MM is 2 inches wide and Fender Js are basically 4 inches apart center which basically leaves you about 3 ¼ inches between their faces less about 3/16s for the screw tower. Whether you wanted to mount a J as neck or bridge is up to you. I don’t put the back face of a pup closer than about 2 inches from where the strings meet the bridge saddles cause pups get too bright (and I’m a bridge player).

    Either way, if the MM is 4 lead or you can make it that way, you could split a coil out of the MM and wire it so the J is humcanceling if you wanted. Unless the J is humbucking, you'll likely get hum through it if isolated.

    Assuming this is a low end bass, you could also just route out a path below the strings (mine are ¾” x 4” x 7”) so you can many any pickup anywhere and just throw down a pickgaurd to cover. After two years of having mine that way, I wouldn’t have a bass any other way.
     
  3. 62bass

    62bass

    Apr 3, 2005
    Thanks Luknfur. I guess I'll just have to take a chance. I talked to Becky at Bill Lawrence this afternoon and she said she didn't think there would be a problem. She cited the fact that the halves of a P pickup setup have poles very close to each other and nobody seems to notice any sonic degradation. It may affect the sound but not in a way that distresses anyone.

    As far as the 2 pickups go, they'll be wired to a switch and it will be a one or the other situation. I don't intend to blend the 2. I very much like the sound of the MM style pickup as is but I would like to also be able to switch to the sound of a single pickup in the traditional neck position; a sound I also like. I will take into account your idea to make sure the pickups attract magnetically, rather than repel, if I can. I'll be going with the Lawrence J45 N. so I shouldn't have a noise problem. Becky says they have them in stock and will be doing another run in February.

    I read your write up of your pickup experiments and learned a lot from them. That's a very extensive body of work. Thanks again.
     
  4. LoveThatBass

    LoveThatBass

    Jun 28, 2004

    It is this altering of the magnetic field by the motion of the steel core string that produces the sound in the first place.
    Anything that would alter the magnetic field such as different strings material, amount of string material, type magnet, number of windings in the magnet and pickup placement can and will affect the tone. Raising and lowering the pickup affects the tone.
     
  5. 62bass

    62bass

    Apr 3, 2005
    Yes, that much I know and on this bass, raising or lowering that big humbucker produces a larger effect in the tone. So, there is going to be some effect on tone from the leakage of magnetic flux between pickups, and I imagine the big humbucker will affect the sound of the J45 more than the J45 affects the humbucker. Then there is the increased magnetic pull on the strings because of the extra pickup.

    So, in the end I just have to take my chances and hope it works. I'll just have to mull it over and see if the expense and work is worth it. At worst, if it doesn't work and I have to remove the J45, I'm left with a hole in the top of a good looking bass that would need to be covered somehow. I don't know if I want that or not.

    Glenn W-thanks for the articles. I managed to understand them. The first one was particularly interesting.
     
  6. 62bass

    62bass

    Apr 3, 2005
    Brilliant! I'll give it a try.
     
  7. 62bass

    62bass

    Apr 3, 2005
    I remember in high school I got this huge Alnico magnet from someone. I stuck it on the door of my locker. I had to get one of the jocks to pull it off. Man, that was strong.
     
  8. 62bass

    62bass

    Apr 3, 2005
    No, he was pleased to do it because he could flex his muscles in front of all us scrawny weaklings and impress the girls. He wasn't all that bright as I remember. He probably would have carried my amp if he could have worn a T shirt. :D
     

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