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Trick to Make a P pickup Hum-cancel with a J?

Discussion in 'Pickups & Electronics [BG]' started by walterw, Jul 29, 2012.


  1. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    i don't often start threads, but this seems pretty interesting, from another thread, and worth its own topic over here i think;
    has anyone heard of such a thing?

    here was my initial response:
     
  2. Stealth

    Stealth

    Feb 5, 2008
    Zagreb, Croatia
    The trick works, as then you can treat both P-pickup halves as essentially one big single coil - all magnets will have the same polarity (and opposite of the J-pickup) and
    the P pickup's windings will be opposing the J-pickup's ones. However, you then only get humcanceling when both pickups are active, and it won't be perfect because of how different the pickups are - but it should buck the hum quite a lot.
     
  3. kesh

    kesh

    Jul 9, 2012
    Brighton, England
    I would rather have a normal split coil P and a hum cancelling J design.
     
  4. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    Me too. However if you just love that single coil sound then you could put a phase reversing switch between the halves of a standard P pickup and effectively make it into a single coil pickup to cancel a single coil J. It should sound fine as a P pickup (because you will switch the switch to the normal position) but when you use both pickups the string signals on two of the strings from the P will be in phase with the J and two will be out of phase. I'm guessing that at least some people will not like the resulting sound, maybe no one would. But it could be done as an experiment.

    Ken
     
  5. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    The P would have to have the same polarity magnets on each half, and be opposite polarity to the J.

    And this would assume you would always use both pickups on at the same time.

    I think there are plenty of hum canceling Jazz pickups that sound just like single coils to not worry about it.
     
  6. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    no good, like you point out, two strings would then be basically unusable.
    yep and yep, but the idea is still interesting, and like i said, i have literally never seen it attempted.

    oh, and i confirmed with a quick phase test that you could indeed physically flip over one P coil and have it output the same signal polarity, just now with opposite magnetic polarity, i.e., the same as the other coil.

    you'd have to re-run the leads to the other sides of the grommets for it to fit under the cover, but that's not too hard.
     
  7. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    Two strings would definitely be different. One man's unusable is sometimes another's signature sound! I'm about to get a P/J but both pickups are hum canceling so I won't be tempted to try this experiment.

    Ken
     
  8. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Search for threads on out-of-phase pickups. Two strings would have pretty much zero low end and very low volume.

    Also, even if you reverse the polarity on one half of a P, it is still a humbucker due to the reversed magnetic polarity on one coil, so it still won't hum cancel with the J.
     
  9. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    No, the string signals on both halves are in phase and the hum signals are out of phase when they are wired normally. If you reverse the wiring on one half the string signals will be out of phase and the hum signals will be in phase.

    Ken
     
  10. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    The only reason the string signals are in phase is because the magnets are reverse polarity. The two coils are wired out of phase. If you reverse the electrical polarity of one coil, it will now be out of phase with the Jazz pickup.

    Also none of the strings are picked up by both coils on a P bass. This is an important distinction between a split coil and regular side-by-side humbucker.

    You can make split coil pickup where one of the two halves would be out of phase with a single coil pickup, or another split coil, and still be hum canceling. Some of the Delanos are made that way and can't be mixed with other pickups.

    The only way to make a P bass pickup act as a non hum canceling single coil is by having the same polarity magnets in both halves, and having them wound or wired in phase.

    But then you wont be able to use the P pickup soloed without hum unless you flip a coil.
     
  11. kesh

    kesh

    Jul 9, 2012
    Brighton, England
    I always wondered why it mattered that the E and A pick ups be in phase with the G and D pick ups. The strings won't have any meaningful phase relationship.

    The only thing I can think of is that each pick up picks up a little bit of the near most string from the other pick up.
     
  12. khutch

    khutch Praise Harp

    Aug 20, 2011
    suburban Chicago
    The magnet polarity affects the string signal, not the hum pickup. The hum cancels in a split P because one coil is wound CW and the other CCW. If you now want the string signals to be in phase you need to use opposite magnetic polarity in the two halves. I am not talking about changing anything about the internal construction of the pickup. I am talking about cutting the wire that joins the two halves of the pickup and swapping the electrical connections between the two halves. It is just like putting a battery in backwards, it will reverse the polarity of both the hum and string signals. So you will now have a pickup that will not hum cancel (but could cancel the hum of another pickup if they are phased correctly) and the string signal polarity will also reverse. I guess that to be precise we cannot say if that will put the string signals between the two halves in or out of phase unless we know if they were in our out of phase to begin with. On a pure P bass it doesn't matter because as you point out each half senses only two strings and the phase between them is a don't care.

    Ken
     
  13. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    Oahu/valco lap steel pickups and the old suhr-designed fender jazz pickups do indeed use two coils end to end with the same magnetic polarity but opposite wind; they hum-cancel, and since there's no string overlap, they sound fine.
     
  14. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    If we really wanted to go down this rabbit hole, you could run your non-RP/RP P pickup pair with the J that was RW/RP from the pair, but use a 3PDT switch to both cut off the J pickup and flip the polarity of one P coil, so that both choices him-canceled to some degree.
     

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