I wanna add a blend pot to my Thunderbird...

Discussion in 'Pickups & Electronics [BG]' started by theFixer, Sep 27, 2017.

  1. theFixer

    theFixer

    May 30, 2017
    Michigan
    I'm afraid I'm a bit of a dullard when it comes to electronics. I'd like to mod my T-bird from it's original V/V/T config., to a V/B/T config. Can anybody direct me to a wiring diagram and the appropriate pot? Thanks!
     
  2. That would be a matter of taste. There are different values and tapers of blend pots that you can choose from, and different wiring schemes.

    Personally, for a passive bass, I would suggest an ungrounded 250k M/N taper blend pot. That gives you the smoothest blending.
     
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  3. theFixer

    theFixer

    May 30, 2017
    Michigan
    What effect does a higher or lower resistance, have on the sound?
     
  4. Higher resistances preserve more treble, but if you go excessively high, the taper will suffer. (On/off switch behavior, rather than smooth blending.) Lower resistances yield a warmer tone by shifting the resonant frequency of the pickups downward. A lower resistance will provide a better taper, but if it is excessively low, the loading on the pickups will be undesirable. With that being said, there are really only two values in usage for passive basses; 250k and 500k. Either will work in your case, so you can choose based on wanting a warmer tone, or a brighter tone.

    Blend pots are traditionally wired like volume pots, which means that each pickup sees two resistances. One is in series, while the other is parallel. A popular mod with blend pots is to leave off each pot's connection to ground, so that there is only the series resistance. The advantage is that you can get a nice smooth taper from a lower value pot (250k), without the typical loading on the pickups. The downside is that it isn't possible to completely solo either pickup. However, most people can only hear the opposite pickup when they tap on its pole pieces.

    As for taper, a typical A/C taper is equivalent to stacking two volume pots on one shaft, with one of them having a backward taper. As you blend the two pickups together, one gets louder while the other gets quieter. This is usually not desirable, as both pickups get attenuated when you are at the center detent. An M/N taper pot keeps both pickups connected directly to the output at the center detent, and then attenuates only one pickup, as you move toward either pickup. At any given point in the rotation, one pickup always stays at full volume. This is arguably the better choice.
     
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  5. theFixer

    theFixer

    May 30, 2017
    Michigan
    One of my T-bird brethren recommended a 500k pot for the 'bird (presumably due to the inherently darker nature of the Thunderbird), and the M/N taper pot sounds like the way I'd wanna go...
     
  6. 40Hz

    40Hz Supporting Member

    May 24, 2006
    home
    What year and version is your TBird? Gibson used 300K and 500K pots for the volume controls depending on the model/year. So you might want to try to get as close to that for starters with your blend if you want to keep what you'll be getting consistent with what you got with separate Vs.

    Alternatively you could just grab a 250K and 500K and see which sounds better to you. That might yield a pleasant surprise.
     
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  7. theFixer

    theFixer

    May 30, 2017
    Michigan
    It's an '08 Korean TB IV.