pots/out of phase question?

Discussion in 'Pickups & Electronics [BG]' started by Mike in Chicago, Feb 22, 2013.

  1. Mike in Chicago

    Mike in Chicago Supporting Member

    Apr 3, 2011
    Before I replace these Duncans, I think I'll get the pots looked at first. All passive, Duncan Precision pickup, and a Jazz quarter pounder from about 15 years ago.

    Here goes...The Precision pickup with the Jazz all the way down, tone anywhere...minimal volume as I rotate from 0 to about 3/4 up then dramatic full volume increase for the last 1/4 way up.

    Jazz pickup...smooth gradual volume increase from 0 to full.

    With the Precision pickup full open...start the Jazz from 0, minimal increase, reaches full about 3/4, finish the rotation and the volume dramatically cuts like it goes out of phase till you bring back to 3/4 where it has the highest volume.

    I don't know much about electronics. 250s 500s? Greek to me. I didn't hook this stuff up...couldn't if I tried.

    When I bought these pickups I think I remember getting a quarter pounder for the bridge cause I was more in my Jaco phase and thought the bridge needed more oomph.

    I was thinking going MV/Blend/tone, and if it balances out nicely like I hope, I may get a Tonestyler.

    Can anyone pinpoint the problem?
  2. Phase issues are related to the wiring of the pickups, not any other part of the circuit. If there is a phase issue, it will be corrected by swapping the hot and ground of one pickup.
  3. Mike in Chicago

    Mike in Chicago Supporting Member

    Apr 3, 2011
    Great. 250s will be good? Ill have them replaced while its apart
  4. Nerevar


    Jun 10, 2008
    Halifax, NS
    Phasing has to do with other things and is unrelated to what your issue is.

    It sounds like the pots you are using have different tapers. On the back it will probably say A or B. A is an log pot and B is a linear pot I believe. If I had to guess they are mismatching.

    And finally the number values are the resistance of the pot. 250 or 500 is common.
  5. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    yeah, sounds like you have an "A" (audio) on the P pickup and a "B" (linear) on the Jazz; a "B" pot for the P pickup will be more even sweeping from off to full.

    also, if this is the classic V/V/T jazz bass wiring, the tone pot can't be set "anywhere", it matters very much here; anywhere but full-up it makes the volumes drop off even faster between say "8" and "10".

    as for the volume drop when the J is full-up, if it sounds "good" with both pickups (kinda mid-scooped, with a little more treble on top), then things are normal, you naturally get a little loss from two pickups in parallel vs one by itself.

    if it sounds thinner and twangier with the J full-up then that pickup is out of polarity with the P pickup and needs to be reversed.
  6. Mike in Chicago

    Mike in Chicago Supporting Member

    Apr 3, 2011
    Thanks guys. Opens up a lot. I've always been the turn everything up then turn the amp up kind. This amp I have now is so f'n loud those different drops in volume/nice tone spots sound kinda nice when the amp gets cranked.

    It's embarrassing after all these years of playing how much of this technical stuff I don't know. Not a clue.

    Outside of all the goofin around, this site really opens you up to lots of info.
  7. jaywa


    May 5, 2008
    Iowa City, IA
    OP... Your issue is EXACTLY what I experienced in my modded 78 Precision and I was using the exact same pickups as you in both the neck and bridge locations. It drove me flippin nuts cause here I had cut up my Precision to get more of a "Geddy" sound with the bridge pickup and it sounded awful whenever I'd dial in even a little of the J.

    But I didn't know any better till I took it to a guy a few years later and he said the two pickups had been wired out of phase.

    As far as the differing tapers... Some guys get really bent out of shape about that kind of thing but for me it's not that big of deal PROVIDED the interaction between the pots is not affecting the strength or quality of signal. You just get used to the tapers as you live with your bass and before long getting the settings you want is 2nd nature.