Problem with left handed Jazz bass wiring

Discussion in 'Pickups & Electronics [BG]' started by billgwx, Jul 30, 2017.


  1. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Hi folks,

    Long time no visit since I've been off playing mostly guitar these days, but when bass beckons I heed the call. I just completed a total rewiring project (or so I thought) for my left handed Jazz bass, including a series/parallel switch. I didn't use a push-pull DPDT pot for the switch/tone control, because I couldn't find any such pots with a reverse log taper, but instead I have the usual VVT setup using CTS 250K lefty pots, and a separate toggle switch for which I drilled a hole in the control plate. All good you say? Well, was I surprised to find the tone control behaving exactly as I wanted, with a nice gradual sweep, but the volume controls behaving more like on-off switches. I want the change in volume to be gradual as well. Faulty pots or a wiring glitch on my part? I figured I couldn't go wrong with a mirror image of this:

    JazzBass_2VppSP_1T.jpg
     
  2. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

  3. That's exactly the problem.

    You wired the pots backwards, so they have the wrong taper for this application. Wire them as shown, or get linear taper pots.
     
  4. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Sure about that? I'm using CTS lefty not standard pots, so wiring them in reverse should have given me the volume taper I desired, as it is doing for the tone control. For reference I flipped the above and compared it to the Fender Standard Jazz Bass LH wiring diagram, and outside of the DPDT switch wiring they look identical. Could the switch be miswired?

     
    Last edited: Jul 31, 2017
  5. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Any J wiring diagram I've come across specifies 250K pots. Not that it means I have to stick with them, but earlier this year I used 500K's in a Telecaster to go along with some high inductance pickups I installed in that guitar and man that thing is too bright...
     
    Last edited: Jul 31, 2017
  6. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Well I'll be damned. Went to the CTS web site hunting for specs, and found that the "lefty" pots I installed are linear taper, not reverse audio. False advertising by a lot of guitar/bass parts suppliers there!

    Oh well, I'll live with it for now since most times I play the pickups mostly either full on or full off, sometimes with the bridge pickup full on and a touch of neck pickup, which may actually be easier to dial in with this taper. Maybe I'll put the old pots back in some time in the future since their volume taper was just fine, or grab some new 250K true reverse log pots via Mouser. Thanks all!
     
    Killed_by_Death likes this.
  7. Well, switching to linear taper for VVT is actually a common mod as it'll give you a more gradual blend with both near full volume. So give it a go for a while, you might like it...

    You can get them on ebay from asia. Here you go...
     
    Killed_by_Death likes this.
  8. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    I like the switch over the push-pull DPDT so no loss there.
     
  9. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    yeah, this makes no sense.

    linear volumes are the same in both directions and for bass are much smoother of a taper than audios.
    the volumes acted like switches at which part of the sweep? if it was between 10 and 9 then you have the "correct" audio taper pots, which is why i don't like them for bass.

    if it was between "1" and "0" then you had righty pots wired backwards.

    actual linear volumes would evenly turn up and down in either direction.
     
  10. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Yep it was between 10 and 9...a little too much.
     
  11. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    alpha-music.com
    then you had the "correct" lefty audio taper pots. (regular stock J basses have the same problem)

    actual linear volumes will fix the issue.
     
  12. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    I wish everyone used Linear volume pots :wideyed:
     
  13. billgwx

    billgwx

    Apr 10, 2009
    Centereach NY
    Thanks again for all your great pointers! They'll have to wait though as life and recording beckon. Most importantly the bass is functional--the tone taper is better than with the push-pull DPDT series/parallel switch I had prior, and the volume tapers are usable as I mentioned above if not ideal. Replacing all the electronics also solved a noise issue, as I hear much less hum when the pickup volumes are uneven. Also, this could be my ears playing tricks on me, but the bass does sound a little different--I suspect that has a lot more to do with going from super light gauge (30-70) hex core GHS Boomers to medium gauge (45-105) round core Boomers to mix it up a bit.
     
  14. tallboybass

    tallboybass Supporting Member Supporting Member

    Feb 25, 2003
    Tulsa, Oklahoma
    I'm a lefty and got perfect taper for the first time in my 45 year career by using a 250k linear pot for volume and a 500k reverse audio pot for tone, in a P bass that needed a bit of brightening.
     
  15. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    It would have been brighter still if you used a 500k Ohm volume pot.
     
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