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Tandem passive tone control for jazz bass?

Discussion in 'Pickups & Electronics [BG]' started by Rich48, Dec 9, 2017.


  1. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    I came across this article on Best Base Gear. Passive Tone Controls Explained | eBass
    Has anyone tried this on their jazz bass. I just picked up a mim jazz and I'm getting very little change in tone adjusting the tone control. The tandem control is made by John East and seems like a quality part.
     
    Last edited: Dec 10, 2017
  2. If you have both pickups at full volume this "tandem" treble cut does nothing special. The value of both capacitances are summed, to provide the total capacitance of the circuit, but...

    if you turn down the volume of one or both pickups, it will provide a slight degree of independence between the two treble cut knobs

    This scenario is best used with a 3-way pickup selector, where you can have each pickup dialed in to the timbre you desire & then switch between soloed pickups.
     
  3. Seems worthless to me.

    Whenever a volume pot is at full, its tone control is a master. You have to turn your volumes down to make use of the tone controls.

    The way that Fender did this in the '60s was to isolate the pickups with resistors, but that means lower output. In short, there is a reason that these kind of schemes are not popular.
     
  4. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    Thank you for your knowledgeable replies. Is it normal for the tone control on a jazz to not do much? It's not too big a deal because I can use the eq controls on my amp to get the tone I want. It just seams strange to me that the control on the base doesn't change much
     
    Killed_by_Death likes this.
  5. That's not normal at all. Try a higher capacitance.
     
  6. Post a photograph of what your treble cut pot looks like now?
    and possibly see if you can get the values off the capacitor...
     
  7. The standard capacitance for high impedance pickups is 0.047uF. This should give plenty of effect. You may try 0.068uF or 0.1uF for a more pronounced effect.
     
  8. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    The bass is a new special addition ash jazz. I also feel that the volume controls are a little strange in that they only make small changes to the volume until they are almost turned fully clockwise. At this point the volume will have a large increase for a small amount of dial movement.
     

    Attached Files:

    Last edited: Dec 10, 2017
  9. The value of your capacitor is standard, however, ceramic capacitors are known to have loose tolerances. Perhaps yours came out on the low side. Try a 0.068uF film capacitor and see how you like the result.

    As for the volume pots, try switching to linear taper. That will smooth out the response by stretching out the range. Audio taper pots are known to give steep dropoffs toward the end of the rotation. Particularly cheaper ones that approximate a log taper by joining a linear segment to a steeper linear segment toward the end.
     
    bigtone23 likes this.
  10. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    This^^^
    Linear taper volumes are great on a Jazz VVT. You can also piggy back another cap to the stock one to increase the value. Add another .015 or .022uF and the tone will get much darker when rolled off.
     
  11. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    Thanks again for your replies and help. After doing a little more research I think I want to switch to a volume, balance, tone configuration. I can order a new harness with upgraded pots and cap from best bass gear that will hopefully solve my issues and give me v/b/t that I prefer. I will update this post after the change. If for some reason you think this is a bad idea, please let me know.
     
    Killed_by_Death likes this.
  12. In that case, go for an M/N taper blend, rather than A/C. Consider leaving the grounds off of the blend pot's wafers, as well.
     
  13. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    Thanks line6man. Where would be the best place to purchase this pot and the lenier taper volume and tone pots? Should I use 250k or 500k pots? Would you be able to point me to a wiring diagram for this configuration?
     
  14. bigtone23

    bigtone23

    Dec 10, 2014
    Denver, CO
    This is that standard wiring for V/B/T. 250K all around is standard J bass.
    The pots you use will depend on what kind of knobs you use-solid or split/splined shafts.

    a8141adb75b5370d_zps00e49acc-. T

    There is a thread that discusses the blend pot. See post #16 about keeping the ground off the wafer.
    Jazz Bass Blend Pot Wiring - HELP!
     
  15. Axstar

    Axstar

    Jul 8, 2016
    East of Eden.
    This seems like an unnecessary mod justified using a faulty, or lazily argued, premise. To dabble in a bit of 'whataboutism', what about the hundreds of professional bassists out there who have used stock Jazz basses their entire career?

    The argument in the article hinges on:

    "A common Jazz Bass issue, as many owners are full aware, is that unless the neck pickup, bridge pickup, or both are at full volume the tone control “feels weak.” The reason for this is due to where the control is in the signal chain. The illustration below is the standard Jazz Bass wiring common to many if not all Jazz Bass models that utilize three controls."

    The article doesn't actually explain this perceived problem very well, and it blames the problem (whatever it may actually be) on where the tone control falls in a typical Jazz Bass circuit. It doesn't say *why* this is the case and doesn't actually say *where* the tone control falls in the circuit, or where it falls in the improved circuit. What is actually suggested in the diagram is that the revised circuit places the tone controls between the pickups and the volume pots, and has to use a dual-gang pot to keep the two pickup circuits isolated before the two meet at the second volume pot.

    Luckily BestBassGear just happen to have the perfect part in stock to make all of this work. Can you say 'corporate shill' or 'solution looking for a problem'?

    The writer of the article doesn't seem very sure of the circuit, however. In the comments below it they assert that 'It is best to use a tandem pot for this'. I would go further and say it is imperative that you use a tandem pot for this, otherwise you are joining the hot outputs of both pickups together ahead of the volume controls, which will stop you from solo'ing either pickup. Ultimately this is a lot of work and wiring to overcome a perceived problem or performance issue the author can't even articulate in any meaningful sense.
     
    fermata likes this.
  16. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    Thanks again for the help. I ordered the parts to make my Jazz have v/b/t controls. For the blend I ordered a Bourns M/N taper 250k pot. I will update the post after getting the parts and trying it out. I'm glad I checked here before ordering the tandem tone control I originally mentioned in my post.
     
  17. Rich48

    Rich48 Supporting Member

    Aug 26, 2017
    Portland Oregon
    While waiting on the pots, I decided to get a pro setup on the jazz and took it to a reputable place. The tech told me the truss rod adjustment was maxed out and the relief was still too high. He suggested I return it to GC and I did. Long story short I ended up exchanging it for a pbass. So I will never know if I would have liked v/b/t better. Thanks again for your help with my questions.
     
    Last edited: Dec 22, 2017
  18. That's the first thing I check out when I get an instrument home, the setup in general, but also making sure the truss rod can do its job.
    That way I don't waste any time or money on it if it's mucked up in some way.
     

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