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Pickup impedance question...

Discussion in 'Pickups & Electronics [BG]' started by JRBrown, Jun 6, 2005.

  1. JRBrown


    Jun 21, 2000
    North Carolina
    Assume the neck pickup in a J bass is 12K Ohms and the bridge pickup is 7K Ohms.

    - What happens to the sound when one pickup is almost twice the impedance of the other?

    - Will the pickup with the lower impedance appear louder?

    - How does the impedance difference impact phasing and frequency cancellations between the two pups?


  2. A9X


    Dec 27, 2003
    Generally, the higher Z pickup will be higher output, but will have less high end. To save me a lot of typing, read this excellent explanation.

    Usually, it will be the other way around.

    Because the pickups by nature are so reactive, ie they vary markedly in amplitude and phase with frequency, and then are loaded by the pots/tone control, the amp input impedance and the capacitance of the cable it's hard to answer without more specific info for the individual application. An exception to this would be where an onboard pre uses a buffered input for each pickup, then all the other effects of the passive controls are moot.

    When you pluck an open E, you get the fundamental at 41Hz, and then a series of harmonics that extend above that up to several kHz. The amplitude and phase of the harmonic structure will vary depending upon how to strike the string, where you strike it, the type/guage of the string and the filter effects of the bass structure itself. Then the pickup placement will determine what the pickup is actually capable of picking up and outputting.
    Here is an excellent graphical description of how all pickup placement affects output.

    Now add all of these together, and you'll get an idea what the ouput will be for a give bass, pickups, placement and electronics configuration.

    I'm sure others will chime in with their own experiences and generalities for placement/types etc.

    I've found enough exceptions that here is no easy answer to the system combination to get a given sound if that's what you're looking for. For example, Alembic and Villex pickups have very different impedances, but the lower Z Alembics certaily don't lack bottom end, and the higher Z Villex aren't missing any at the top.
  3. luknfur


    Jan 14, 2004

    If that don't ring your chimes, nothing will.

    (and now you know where Brett got his screen name :- )

    Seriously, some great links Aussie.

    However, if you're like me and don't live in the research triangle in NC, I will dish out some homeboy chime with a little help from another from Dixie (Lyle Caldwell's Leo LTD).


    Leo was more my speed in that the only way I know is to do it. As someone once sang, "Its in the way that you use it." I'd speculate if you use a lot of one and very little of the other - won't matter. Probably the more of an equal mix of each the more a problem would be inclined to arise.

    I mix pups all the time including actives and passives and never had a problem - but I run each pup straight to seperate jacks into seperate channels of the same amp. So they're basically independent. However, there is a seperate/combine switch for the amp channels and I frequently bounce back and forth between the two to alter tone. And I'll get phasing issues with pups through the amp just like I would onboard when using the combine channel. So I would guess I'd have got some Dr Who in the mix when combining pups at some point if impedence mis-matches were a serious threat. But I've definetly read related comments of caution.

    Personally, I'd be suprised if there was any problem at all but it's not like it would be the first time I was suprised - or the last.

    Actually, I would think manufacturers would tend to make the bridge much higher impedance than the neck pup to compensate for the volume loss of bridge placement. And from what I know, it would take more like a 12 - 4 not 12 - 7 to pull a fairly even balance off for a typical bridge to neck placement.

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