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Isolating tone controls from two pickups

Discussion in 'Pickups & Electronics [BG]' started by Stealth, Apr 14, 2009.

  1. Stealth


    Feb 5, 2008
    Zagreb, Croatia
    Suppose you had a two-pickup bass, each with its own V/T stack. Considering tone controls commonly interfere with each other if the pickups are later connected into a parallel (turning one will necessarily affect the other as well), is there any way to somehow have each of the tone controls function independently on its respective pickup?
  2. spode master

    spode master

    Jan 21, 2007
    Yes, a buffer after each tone and volume control, then a summing amp. Basically 3 op amp or discrete buffer channels.

    Assuming you are using two volume and 2 tone controls
  3. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Yep, you need to step beyond passive into active circuitry at some point if you want isolation and more definitive control. Whether you do this on the bass or downstream, that's what it takes.

    One way a few do it is just to have separate outputs from each pickup, to separate signal chains.
  4. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    certain old danelectro basses had their two single coil pickups in series, at which point the individual tone pots were isolated. it made for a surprisingly useful effect, as since you could kill the highs of just one coil, you could effectively have the low frequencies being heard by both coils (series fatness) and the highs by just one (single coil clarity).
  5. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    On passive instruments the controls will always interact. That's probably why fender stopped putting two tone controls on Jazz basses.
  6. GlennW


    Sep 6, 2006
    I had a two pickup bass set up so each pickup went to its own 6-position rotary switch that went Off, .1, .069, .047, .033, .022.

    I thought it would add flexibility by having one pickup bright and the other dark...didn't work all that great. It's one of those ideas that seems a lot better thinking about it than it sounds in real life. I changed it to one switch to select pickups and Off, and the other switch for caps.
  7. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    It is a cool idea to roll the highs off the neck and some lows off the bridge when you mix them together, you eliminate some phase cancelations and overlaps, but it doesn't work well passive.

    I guess that's why stereo instruments were made.

    I was going to stick a preamp with bass/treble for each pickup in one of my basses, but then I used the other preamp in another bass.

    I think it's still a cool idea though.
  8. UncleBalsamic


    Jul 8, 2007
    This probably wouldn't work, but couldn't you put a diode after the tone pots?
  9. mje


    Aug 1, 2002
    Southeast Michigan
  10. GlennW


    Sep 6, 2006
    It didn't do anything that couldn't be done with a master tone switch and fiddling with the amp a little. All those caps take up a lot of space too.
  11. no...the diode will create a small forward voltage problem to overcome...this could act like a "gate" on your signal and kill your sustain...heck, if the Vf is high enough, the entire signal could be killed.

    for eliminating interaction, active buffer is the suitable solution.

  12. HogieWan


    Feb 4, 2008
    Lafayette, LA
    how is a les paul guitar wired - it has separate vol and tone controls for each pickup and is a passive instrument
  13. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    A diode might cause a little clipping. That Black Ice Passaic distortion thing is a couple of diodes.

    I used to wire up diodes where you would out the tone cap for built in passive overdrive. Jack Bruce had one in his Gibson basses.

    A couple of resistors would add some isolation at the expense of reducing the output.
  14. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    The Les Paul has a switch that lets you select each pickup individually, therefore it makes sense to have a tone control for each.

    The tone controls will interact when both pickups are selected.
  15. What about a Ric4001/3 in stereo? I've always been a bit annoyed by this phenominon.
  16. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Les Pauls also have the problem of one volume control effecting both pickups when you have them both on. If you turn one pickup off, they are both off.

    Rics in stereo have separation as long as you have each pickup going into a separate input or two amps.

    But really why would you want to remove the highs from one pickup and not the other? It seems like a good idea until you try it and then it doesn't sound all that much different.
  17. Stealth


    Feb 5, 2008
    Zagreb, Croatia
    Well, the wiring layout I made (as a purely mental exercise) was supposed to go mono/stereo. The stereo not interfering with itself makes sense considering the output branches from each of the pickups is split into two channels that aren't connected anywhere...

    However, if I have a Mono/Stereo wiring (similar to the RickenBucker diagram on the Seymour Duncan site), am I correct in assuming that I better use an on/off switch for the mono output, because without it even the stereo tone will get mixed and I'll get tone-pot interference due to the fact the signals mix in the mono output branch?

    My common sense just isn't tingling these days - ergo the slightly silly question. :smug:'
  18. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    The tone pot shunts highs to ground via the capacitor. You have to have the pickups isolated from each other totally for the tone control to work only on one PUP and not the other. And the way passive electronics work, there aren't many good options for creating that isolation. The original wiring for the Fender Jazz Bass used resistors to isolate the signals, but it also reduced the output level of the system. So for the Vintage Series reissues, they elected not to use the resistors, but the tone controls interact.

    They don't on a Gibson style instrument only if the switch is soloing the PUP. That's becasue the switch isolates the control circuit for the bridge PUP from the neck PUP totall- if you have only the one PUP selected. If you put the toggle in the middle, either tone control will cut the highs.


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