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jazzbass pickups out of phase ???

Discussion in 'Basses [BG]' started by George Looney, Jul 24, 2002.


  1. I recently noticed that my jazzbass (cheap copy, passive) sounded weaker when using both pickups and stronger (and better) when using only one.
    I removed the pickguard and unscrewed the controls. I saw that the wires from each pickup are mounted in reverse. (neck PU : black wire to Vol pot 1 and white wire to ground / bridge PU : white wire to Vol pot 2 and black wire to ground)
    So the pickups are out of phase, right ?
    If so, is this normal (standard) for a jazzbass ?
    Do out of phase pickups have a hum-cancelling function ? (I can't really see another reason for it)
    Any help would be greatly appreciated, thanks.
     
  2. I've found a lot of (original) wiring diagrams for various Jazzbasses, and the pickups on all of them are in phase ... (at least I think so, because the PU wires are defenitely not mounted in reverse)
    Here's where I found the diagrams : http://www.mrgearhead.com/

    I guess I've already found the answer to one of my questions, but I'm still not a 100% sure ...

    Another question : does the phase of the pickups affect tone ?
     
  3. lost_in_space

    lost_in_space

    Nov 16, 2001
    France
    hi

    phase relationship between pickups alters tone a lot. when two pu's are wired out of phase respective to each other, a lot of the signal is cancelled out and the output is weak and the tone is i would say "hollow" (most of the spectrum is gone, leaving only upper harmonics plus rumble & noise). this is (as far as i know) not good for bass. sounds interesting for guitar. some guitars have a phase switch which i think is a definite plus: many 70s gibsons have that.

    make sure your bass is wired in phase, you'll hear the difference immediately.

    hum cancelling is as you rightly guessed based on phase opposition; humbuckers contain two coils which are wired in opposite directions and phase out difference signals, hence killing extraneous noise. this is the opposite from wiring two same pickups in reverse (which phases out the equal signal) and does not affect tone.

    regards
     
  4. Thanks Lost_in_space ... guess it's time to take out the soldering-iron.
     
  5. I did it, rewired the whole thing, added shielding and removed the groundloops.
    I followed the schematic of a vintage Fender Jazzbass '75. (wich was also shielded)
    The results are great, I can't believe it's the same bass !!! No hum, no noise, just very nice and clear tone, I've should of done this a long time ago.

    Since all off my questions have been answered and because off the overwhelmingly massive response to this thread, I see myself forced to close it ...

    Thanks again Lost_in_space