Phase inversion of half the P pickup, who did this ?

Discussion in 'Pickups & Electronics [BG]' started by Nunien, Apr 28, 2021.

  1. Nunien


    Mar 22, 2020
    Hi I just got an Ibanez sr1000e from around 1987 and first thing I noticed was a weird lack of low frequencies. Actually the problem came only when the P and J pickups was blended. Each pickup played on it's own had plenty of lows, no problemo. Also I noticed that the problem was only about the E and A strings, D and G were fine.

    So I thought it was a phase cancelling between half the precision pickup and the jazz pickup. I rewired the upper side of the precision pickup and it worked very much better.

    The weird thing is that I noticed no signs of odd jobs inside the bass. So how is it possible that no one, since 1987, noticed an obvious problem that took me 30 minutes to analyse and fix? Is it possible that it came out of the factory like this? Are there people that prefer to play like that? Who did this???
  2. crguti


    Feb 14, 2011
    You should ask that to the previous owner.
  3. MattZilla


    Jun 26, 2013
    How is it possible that you aren’t considering that someone in the last three or five years tried to scam a pawn shop into giving them $100 for the bass and then buying it back a year or so later for $50 because of the faulty wiring?

    more than 0.00% likely.


    Ray Davies.
    markanini and kesslari like this.
  4. Nunien


    Mar 22, 2020
    I doubt it because you had to have experience with basses to ear the problem and I don't think sellers at pawn shop would trust a client that say "listen to that, the sound is weird give me 50%" if they aren't convinced of the problem.
    And where I live the pawn shop would give you only 50% of the price you could sell it on internet so it would be a very risky scam. And the bass costed me 350€.
  5. Nunien


    Mar 22, 2020
    The previous owner had no clue.
  6. Nunien


    Mar 22, 2020
    Is this a joke? I don't have the reference.
  7. JKos


    Oct 26, 2010
    Surprise, AZ
    An interesting question is whether the P was in a hum cancelling configuration before your fix or is now.
  8. Nunien


    Mar 22, 2020
    I have no idea about that. How can I check that, should I try to make the pickup hum?
    >edit : just check, there is a slight hum with the p alone, no hum with j alone.

    I only switch the only two wires that were coming from the upper half of the p pickup.
    Last edited: May 4, 2021
  9. Nunien


    Mar 22, 2020
    Can a P pickup from 1987 have a hum cancellation system? I noticed metallic plates
    underneath the pickup, doesn't it mean that it doesn't have hum cancellation?

    The pickups are stock PJ-IBZ/USA C2 made by DiMarzio
    I've found this if it helps :

  10. Jazz Ad

    Jazz Ad Mi la ré sol

    P pickups, cancelling hums since 1957. When wired the right way.
    MattZilla likes this.
  11. Nunien


    Mar 22, 2020
    Oh, this is getting interesting.

    After reading this P-Bass hum suddenly worse I want to add that the hum (which is very light) isn't affected by touching the strings or not. But the hum do vary when changing the orientation of the bass.
  12. JKos


    Oct 26, 2010
    Surprise, AZ
    There are two ways for a split P pickup to be hum canceling (as they are intended to be).

    1) The two halves of the split pickup are identical and one wired opposite polarity of the other. In a single pickup bass (or mode), this works fine as the relative difference in phase does not matter as each string is only sensed by one half of the pickup. The opposite polarity wiring cancels hum. However, when combined with another pickup, two strings will be in phase and two out of phase.

    2) One half of the split pickup is reverse-wound reverse-polarity of the other. This is how normal humbuckers (non-split) are made. This method allows both halves to be in phase with other pickups.

    It would appear you have situation 1.
  13. Nunien


    Mar 22, 2020
    Thank you very much for your help.

    So my understanding is that I have in my P/J bass a P pickup that is meant to be alone and is not compatible with a paired Jazz pickup.
    Could it be possible that one half of the P have been mounted upside down in it's casing or smth like that ?

    Is there a way for me to check the way of the wounding ?