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Precision Bass wiring variations and capacitor value

Discussion in 'Pickups & Electronics [BG]' started by Banksy76, Dec 15, 2018.


  1. Banksy76

    Banksy76

    Nov 5, 2013
    I intend on rewiring a P-Bass of mine, upgrading the pickups, and using it as a project to develop my understand of such things. In my research I have found a few variations of how to wire up a precision bass and even Fenders website provides different methods for their standard American Precision and their Vintage. What difference to sound/tone/operation would you expect from these 2 different wiring methods below and what would the difference in the value of the capacitors make? Many thanks in advance.
     

    Attached Files:

    Alain Decont likes this.
  2. Slater

    Slater Leave that thing alone. Supporting Member

    Apr 17, 2000
    The Great Lakes State
    There should be no difference in tone between the two methods of wiring. The .1uF cap will take away more treble than the .05uF tone cap.
     
  3. Banksy76

    Banksy76

    Nov 5, 2013
    Thank you for your response and info provided.

    Regarding the .1uF cap, I'm assuming that this will not result in less treble with the pot fully open, only a greater reduction when attenuating?

    So the 'Vintage' Fender P-Bass tone is as much to do with the tone pot capacitor value as it is the pickups installed?

    In addition to the 2 diagrams contained in my opening post, are there any other methods of wiring the passive p-bass?
     
    Pbassmanca likes this.
  4. ex-tension

    ex-tension

    Jun 11, 2009
  5. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    The two wiring diagrams sound the same. FWIW, I prefer the non-vintage wiring because I prefer a wire (instead of the cap) bridging the pots. If a pot comes loose and turns, that cap leg wire breaks pretty easily whereas a wire has more flexibility and is much less likely to short out on a solder tab on the pots.
     
  6. Slater

    Slater Leave that thing alone. Supporting Member

    Apr 17, 2000
    The Great Lakes State
    Correct. There won’t be much of a difference until you reach the last 1/4 turn or so of the pot. See the videos that @ex-tension posted a link to.
     
  7. 40Hz

    40Hz Supporting Member

    Probably. But wiring diagrams (often mistakenly called “schematics”) only show the physical layout of an electronic circuit.

    A true schematic view shows the funtional design of an electronic circuit.

    As long as one physical wiring scheme produces the same electronic circuit as shown in the schematic, then (from an electronics perspective) it’s the same as any other wiring scheme that also does so.

    tl:dr - There’s multiple ways to wire up something to produce the same electronic circuit.
     
  8. Banksy76

    Banksy76

    Nov 5, 2013
    Thank you all so much for taking the time to reply, your feedback has been most helpful and really appreciated. With the info which you have provided above, along with the video that ex-tension provided a link to (top job on that video by the way Robbie K!), I feel that I have got my head around the basics of the wiring of the p-bass and the influence that the tone cap has on the audio. What I'm now trying to establish is how best to determine which value the volume and tone pots should be, 250K or 500K. I appreciate that ultimately this all comes down to personal opinion and preference but is there a general rule of thumb here, does the impedance of the pickup/s typically dictate the resistance value of the potentiometer? Also upon looking at some of the pots that I have found installed in my bass guitars, I have some marked A which I understand is logarithmic/Audio , B which in Linear, but what the hell are these pots marked with D?
     
  9. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    D taper has a deeper curve than audio taper. It drops resistance faster.
     
  10. Banksy76

    Banksy76

    Nov 5, 2013
    Thanks for explaining that, just I've never been aware of a D taper until now. So any reason why a D-pot would be used instead of a regular A for either the tone or volume control?

    And is the preference between 250K and 500k volume and tone pots often determined by the impedance of the pickups?
     
  11. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    I imagine a D taper would be better for a volume pot for guitarists playing with distortion. It will clean up faster as you roll down the volume.
    Stock P bass is 250K audio for both. I think that may have been influenced by Fender only needing to order one type of pot for both controls, keeping the parts ordering and assembly more simple and foolproof.

    My favorite is linear taper volumes and audio taper tones. Linear volumes don't turn down as fast, giving you more precise control of your volume setting. It's especially nice on a VVT set up for more precise blends.
    As far as 250 vs 500K, that's more of a preference thing.
    A 500K volume has less resistance and will make for a touch brighter overall tone vs a 250K. Similar for the tone pot: if you want an extra shot of clarity, use 500K here too. You can always turn the tone control down to 7 or 8 to have the same tone setting as a 250K pot.
    If you are using vintage output pickups, 250K is fine for both. If they are hot or overwound, the 500K are nice to retain some high end. It's also sometimes nice to mix a 250K linear volume pot with a 500K audio tone pot. You get a nice, smooth taper on the 250K volume and a slightly wider tonal palate with the 500K tone.
    I recently rewired my P/J with a set of Wilde P46/J45L and used a 500K linear volume, 250K M/N blend and 500K audio tone with .047uF cap. The Wildes are fairly vintage output, but I wanted to get extra clarity out of them and reduce the loading of having two pickups and 3 pots (technically 4 since it's a stacked blend). It's easy enough to back off the treble on the amp or the tone control to darken the tone. It works and sounds great.
     
  12. Banksy76

    Banksy76

    Nov 5, 2013
    Thanks again bigtone23, this is most insightful and informative.
     
  13. Banksy76

    Banksy76

    Nov 5, 2013
    It seems that my Squier Vintage Modified Jazz Bass has 500K pots for each of the volume pots and its tone pot. I'm curious to know what difference 250K pots would have on the sound but instead of going to the bother of unsoldering all the wires and swapping each of the pots out, couldn't I just add a resistor to a 500k to essentially turn it into a 250K pot?
     
  14. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    You can add a parallel resistor to the pot to make it 'see' closer to 250K. Typically, this is a 470K or 510K resistor. Wire it to the outside lugs of the pots and you are done. The catch is that this can change the taper, for better or worse, but tonally you will have a better idea of what a pot value change will have on your bass.
    Rparalel.
     

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