Wiring Bartolini NTBT-918 pre-amp with passive tone?

Discussion in 'Pickups & Electronics [BG]' started by Groovecenter, Jun 5, 2003.

  1. Can the Bartolini NTBT-918 two band pre/amp that comes wired in the Vol/Blend Stacked treble/bass be wired so that a fourth knob acts as a regular tone control? (in both passive and active modes)

    If someone could post a website with a diagram for that, or offer advice or anything, it;d be appreciated. Thanks
  2. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    Well here's what I would do. Since you want it to work active/passive you have to add it in between the preamp and the pickups.

    What you could do is tap into the hot line of each pickup and run a lead to a pot which bleeds off the highs through a capacitor to ground.

    Look in the drawing here http://www.seymourduncan.com/website/support/schematics/standard_pbass.html and see how a hot wire gets bled to ground through a cap. You can get a stacked double pot and just do the same thing for each pickup.

    So adding a stacked pot you'd have a wire from one pickup going to the center lug of one pot with the side lug connecting to a capacitor leading to ground. Then the other pickup would go to the center of the other pot and have it's own cap leading to ground. This should allow you to still use the blend in active mode and would even allow you to have a different value cap for each pickup.

    If you can post the schematic you have so far without the passive tone I could probably draw it in for you.

    A passive tone is very similar to a volume, it basically varies how much of your signal you send to ground and therefore silence. The capacitor only lets high frequencies get through so in a tone knob only highs are allowed to be grounded. it becomes a partial volume knob in a way.

    Good luck and don't burn your fingers :)
  3. Moo

    Moo Banned

    Dec 14, 2002
    Oakland, CA
    ... or you could get a concentric pot


    and have a tone knob for each pickup.

    Passive pickups I presume? Then you'd want 250k for stock fender types or 500k for high output screamers. Active would need somewhere between 10 and 50k. Larger values give you a sharper rolloff and if you just go for a stacked pot you can find linear vs. analog tapers which I find much more even in tone rolloff.