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Jazz Bass "scooping" mids and lows at full volume, why?

Discussion in 'Basses [BG]' started by whovines, Jun 27, 2012.

  1. whovines


    Jun 3, 2012

    Just got a 2012 AM ST Jazz Bass. I typically purchase from brick and mortar, but decided to go online to avoid the grubby hands at GC. As luck would have it, she took a road trip across the country all of last week (while some of you were enjoying a little heat wave... Needless to say, a little TLC was in order upon arrival).

    Upon plugging her in, I found that when both volumes are 100% the overall sound had scooped mid and lows (no matter where tone is set), and the volume was slightly reduced.. Basically, creating an exaggerated bridge sound, with no bass and few mids (and slightly tinny).. When I pull back either the neck or bridge volume to about 70-80% (while keeping the other at 100%) the full tone is restored...

    Anyone care to speculate? Am I just tripping and the bridge pickup is simply too high?

    This is my first Jazz bass, and so I've been reading the various posts about log vs. of linear pots, reverse-wound-reverse-polarity, parallel wiring - all of which are extremely sexy and blowing my mind....
  2. TheEmptyCell

    TheEmptyCell Bearded Dingwall Enthusiast Banned

    This is just the way the pickups work on a J bass. I don't remember the fancy terms for it, but it happens to every single J bass.
  3. seang15


    Aug 28, 2008
    Cary NC
    Strange, sounds like it's wired out of phase. This was purchased new?
  4. Ewo

    Ewo a/k/a Steve Cooper Supporting Member

    Apr 2, 2008
    Huntington WV
    AFAIK, the stock wiring on a J bass is with the two single coil pups wired out of phase, to cancel hum.

    If you solo either pup, you're likely to hear 60 cycle hum. With both pups up the same amount, the hum gets nulled.
  5. john m

    john m Supporting Member

    Jan 15, 2006
    My friend had one in 1975 and I remember it being "weird" that way.

    I recently acquired (and sold) a 1984 Steinberger.
    I was told by the previous owner that the pickups and knobs were wired like a Fender Jazz bass.

    I remember some loss of tone when both pu's were up full.

    I'm sure there's info on this.......sounds normal for a j bass
  6. whovines


    Jun 3, 2012
    Yes, purchased new.

    I was beginning to think all Jazz basses work like this.. I saw the similar thread about volume/tone prefs. If this is the way it is, I dont see how the 100/100% sound is desirable.
  7. whovines


    Jun 3, 2012
    Thanks for the quick responses!

    I'm getting more than the 60Hz nulled with both volumes the same...
  8. Ewo

    Ewo a/k/a Steve Cooper Supporting Member

    Apr 2, 2008
    Huntington WV
    De gustibus non est disputandum, eh?

    I like that scoop; it's why I favor J configuration on my basses.
  9. Kael


    Dec 26, 2004
    Oklahoma City
    Wire a push/pull pot on the neck volume that sets the pickups in series. It will give you more mids/volume and avoid that mid-scoop when you are using both pickups full blast. It will also allow you to still have access to the classic J scoop tone if you want it by disengaging the series mode.

    This mod costs less than ten bucks and is 100% reversible.

    PS: It is the mids that are scooped not the lows. The lows are still there, but they may seem to be reduced due to lower low mid output.
  10. whovines


    Jun 3, 2012
    Let me re-phrase.. I like that sound/taste sometimes, too, but it's not what I expected to happen with both pups at full volume. Especially when slightly pulling back one yields the other end of the spectrum: the lovely low growl.
  11. Kael


    Dec 26, 2004
    Oklahoma City
    When you set both volumes at same level the pickups are loading each other. It is not uncommon for a J player to routinely back one pickup off full to get the volume bump and the growly mids back in the mix.

    There are also a couple preamps out there that offer a buffered blend that prevents the pickups loading each other. Of course, adding a preamp is a matter of taste. I find that I prefer passive these days.
  12. seedokebass


    Mar 21, 2009
    Same here. It just sounds good!
  13. whovines


    Jun 3, 2012
    Considering the push-pull mod... Thanks!
  14. Asomodai


    Jan 21, 2006
    London UK
    Are either one of the pickups especially quieter then the other? If that's the case, switch the pup wires over on the pickup that is quieter. Should get a much better sound and much less volume reduction. It happened to one of my jazz's.
  15. That scoop is completely my idea of typical Jazz Bass Sound and i love it. It can support those heavy guitars perfectly. Who needs deep bass anyways? Both Fender Classix nail the right frequency (their own special spot each, though) to fit into most styles of music.

    If you have space, the P-Bass will just kill. If arrangements get thick, i grab the Jazz Bass. It can be clearly heard and give solid foundation without mudding. It also has a very pleasant tone when heard alone.
    The low end growl you mentioned when the bridge PU has more Volume than the neck PU is also a trademark sound. Even the Neck PU heavy sound can be very cool. But what you describe is exactly what i expect from a jazz bass, and had four different of them: Squier CV 60's, Mex Classic 60's, Standard Mex Jazz and now the US Standard. If it wouldnt scoop, i wouldnt have that bass.
  16. mongo2


    Feb 17, 2008
    Da Shaw
    It's due to the comb filtering of the magnetotropic convolution about the poles of inverse electrostatic divergence.
    Herrick likes this.
  17. ToneMonkey


    Sep 27, 2003
    Newberg, OR
    J bass pickups are reverse-wound with respect to each other, not out of phase. Same thing with a split P set. Big difference. Out of phase pickups would cancel each other's signal out (no output at all with each PU at the same volume), whereas reverse-wound PUs simply cancel noise.

    Agree that every J bass I've played exhibits the "scooping" mentioned by the OP. I believe that it's a comb filtering effect caused by blending two PUs that are relatively close together. Strats exhibit this in spades, while teles do not do it much because the PUs are farther apart.

  18. phillybass101


    Jan 12, 2011
    Artist, Trickfish Amplification Bartolini Emerging Artist, MTD Kingston Emerging Artist. Artist, Tsunami Cables
    Exactly. Man just play the thing. Marcus Miller who is Mr. Jazz Bass plays with his pickups at full blast and relies on the house to bring his volume up. Could Marcus be wrong about making a Jazz Bass sound good? If you're this technical about a Jazz Bass which only has two passive pickups and electronics maybe you should consider being an engineer. Oh wait I forgot to turn my metronome off as I was practicing arpeggios through the scale degrees. What I'm trying to imply is, if your stuck on how the JB works, and spending time trying to tweak a brand new bass there is another guy paying attention to the important stuff and practicing his azz off.
  19. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Yes and no.

    The magnets have opposite polarity, so that puts the pickups back in phase in regards to the strings, but not the noise. Also they aren't wired out of phase, but are wound in opposite directions.

    If this bass is loosing low end with both pickups on, then they are either wired up out of phase by mistake, or the magnets are the same polarity. The comb filtering won't remove low end, just mids.

    Does the bass hum with both pickups on?
  20. MonetBass

    MonetBass ♪ Just listen ♫ Supporting Member

    Sep 15, 2006
    Tulsa, OK
    Bump the mids on your amp, or put a pre-amp on the bass and bump the mids there. :bassist:

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