The perfect jazz bass sound... without any pots (help needed)

Discussion in 'Pickups & Electronics [BG]' started by Luke the Fluke, Jul 17, 2017.


  1. Imagine you have a jazz bass - plug it in and then turn it up to play lovely scooped Miss jazz bass tone ... now imagine you do the common thing of very slightly rolling off one of the volumes so the mids come back.

    Right now imagine that rather than two volumes I wanted a sellector switch:
    pickup 1 - both pickups - pickup 2

    I wouldn't be able to have the setting where one volume is slightly rolled off would I?
    So I should be able to wire it with a couple of resistors so the switch goes:
    Pickup 1 - both pickups (pickup 2 slightly attenuated) - both pickups (full on) - both pickups (pickup 1 slightly attenuated) - pickup 2

    Any of the clever folk on here know what value of resistor would give me a slight attenuation so that the mids come back, but without killing the volume of the pup altogether?
    My first guess is that if a jazz bass uses 250k pots then a 25k resistor would get me about there?
     
  2. 20k?
    50k?
     
  3. Thats kinda what I was thinking - but the mini pot is just a variable resistor isn't it - so I should be able to work out what that is and then substitute for a non variable resistor. Might need to get a 250k pot and multimeter and experiment.

    The confusing thing is I haven't fully explained what I'm trying to do...
     
  4. Standard setup for active bass is volumes and blends fed into a preamp to do the tone shaping.

    Stingray preamp has the pickup going straight into the preamp and the volume actually the output stage of the preamp.
    So if I want to add a second pickup to the stingray influenced bass I'm building I want to use switches between the pickup and input to the preamp .... except if I put the pickups into single coil mode there is that "slightly roll off one of the pickups" effect I want to recreate.
    So if the 250k pot reads 300k at that point the passive setup like you've drawn would be a 300k resistor - but for me I think 50k would be where I start...
     
  5. SteveCS

    SteveCS

    Nov 19, 2014
    UK
    If you want to really replicate things, you will need 4 resistors to create voltage dividers and load the pickups in the same way the pots do. So if at the top (hot to out) you have say 50k, put 200k between hot and ground.
    All IMHO, and YMMV...
     
    Crater likes this.
  6. RobbieK

    RobbieK

    Jun 14, 2003
    Yeah, just one resistor should do. If you think about an unearthed MN blend pot, then in the middle, the pickups are summed with no resistance, then as you turn it one way, you are simply adding a single resistor in-line with one pickup, while the other remains hardwired to the output.

    A rotary switch can be wired to replicate this. I used to do this back in the 90's because MN blend pots were pretty hard to come by and expensive, pre-ebay etc. But rotary switches were (and still are) cheap and easy to find in retail. You need a 2-pole switch. A 5-way makes more sense I guess, but a 2-pole/6-way will be just as cheap and you can set an extra blend.

    To set the blend, you can, as you said tack in a pot and measure the resistance. If you are decent with the soldering iron, you could probably also mount a couple of trim pots to the switch as well, so you could tweak them if needed.
     
  7. SteveCS

    SteveCS

    Nov 19, 2014
    UK
    Another option might be to keep the VVT but put a small resistor (10-25k but you'd have to experiment ) in series after one of the pots. With both dimed, ie easy to find, you get the 'not quite' blend required, but you can still get the scooped blend if needed by rolling back the other volume and you still have most of the VVT capabilities intact. IME the difference between 100/100 and 95/95, although discernable, is marginal.
    Just thinking aloud...
     
  8. SteveCS

    SteveCS

    Nov 19, 2014
    UK
    Like this...
    IMG_20170718_143433.JPG
     
  9. wiring.

    this is what I'm planning....
     
  10. Of the four resistances, one is zero Ohms, and two are parallel to each other. So that reduces to two resistors. However, one of those two is just parallel to both pickups, so it serves no purpose in the OP's scheme. Hence, only one resistor is needed.
     
    Rich Fiscus likes this.
  11. RobbieK

    RobbieK

    Jun 14, 2003
    Yep, that's exactly what I was talking about. I've wired this type of thing many times. (In fact the bass in my avitar pic has something similar these days.) The resistor can be wired to the switch lugs, then the resistor tail can weave between the other lugs as hook-up wire.

    However, with a MM 2-band pre, you may get some switch noise. This is because rotary switches are usually not MBB (make-before-break). That means that the input of the pre is not connected just for a split second as you go between switch settings. This is time enough for the input cap to charge (it is 4.5v on its other side). You should be able to fix this with a resistor from the input of the pre down to earth. A 1M to 2.2M resistor should do the trick.
     
  12. Since you won't be blending pickups, I picture you'll get the following config:

    1. BUzzzzz...Bridge Pickup only
    2. Silence...Both Pickups (yeah!)
    3. BUzzzzz...Neck Pickup only :)bawl:)

    But why not, experimenting is fun.

    Now, keep in mind that every wiring, or pickup config the human brain can possibly conceive or imagine has been tried already...and not been adopted by other players usually for a reason.

    Installing a passive Stellartone filter will take you closer to your sonic goal, you'll get exactly the sound you described and still keep the option of blending the pickups with a VVT config. IMO
     
    hondo4life likes this.
  13. :) a good hour pouring over spec sheets means I've got myself a 2-6 position (I'll set it to 5 position) make before break switch .... or it should be - is there a way to test it?
     
  14. it won't be that bad - as I'll only get possible troubling buzz in single coil mode- the pups are humbuckers.it means I'll get the stingray sound, something similar to my G&L L1000 or P bass and a approximation of a jazz sound (the bridge pup coil isn't quite in the right place) the other settings are bonuses if they work out.
     
  15. Ahhhh! It'll work then. But again look into a Stellartone as a simplier option.
     
  16. hondo4life

    hondo4life

    Feb 29, 2016
    SC
    What is this Stellartone thing? Don't answer that. I just watched every Youtube video demonstration. I am definitely getting one.
     
  17. I've looked up the Stellartone stuff - not for me I think. Firstly cos it would cost too much, and secondly cos it looks like more of a tone control than pickup switching - which is cool, but a varitone + a preamp - way too complex when you're using it. I think it's cos you can't "see" it like you can pickup switching.
    I may be slightly biased by my warwick thumb pickups - they are these active seymore duncan's with tone shaping on the pickup - 8 different options per pickup... that's 64 variations before you get to blend and the preamp. To much! :)
     
  18. A more practical option is to put a handful of well-chosen capacitors on a rotary switch. Cheap, simple, and useful.
     
  19. hondo4life

    hondo4life

    Feb 29, 2016
    SC
    I just want the "simple" 6-way tone control thingy in place of the standard tone pot on a passive P-bass. I think it's $85. Not cheap cheap, but not bad.
     
  20. AcridSaint

    AcridSaint ベーシスト Supporting Member

    Jan 30, 2012
    Raleigh
    I don't play well.
    Why not put a dual concentric pot in place of one of your volumes? Then when you select both pickups, you can roll off the volume however you like.