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Passive tone into a Thumb system

Discussion in 'Pickups & Electronics [BG]' started by bajerovaquero, Mar 5, 2014.

  1. Hello
    I´m installing a used Warwick Thumb pickups and preamp in another instrument.
    It has 4 holes so I was wondering about adding a passive tone to fill the 4th hole. Makes a lot of sense because you cant shape the tone in passive mode anyway...

    Is this a straight operation I mean hot to 250k pot with capacitor and ground?
    Let me know if it would work or the extra resistor will interact with the active system.

  2. Some Warwicks have active pickups. If that's the case, you will want a lower value pot.
  3. RobbieK


    Jun 14, 2003
    ^ true dat.

    also, some people like to run a passive tone pot from the bypass switch so it only kicks in when the bass is switched to passive mode.
  4. Thanks for your responses! I appreciate

    Here is the wiring diagram:

    There are pots of 500 100 and 25k ....
    I¨m going to wire first a 500k pot between hot and jack and listen what happens if not work then a 50K

    Also I got some 250k dpdt pot so could you provide some schematic RobbieK?


  5. The pickups are clearly stated to be active. This means you should use a 25k tone pot. (Or 50k, to taste.) Additionally, you may want to try higher capacitances than would typically be used for passive pickups, because the frequency cutoff point of a tone control is partly dependent on signal impedance. 0.1uF is a good place to start.

    Note that tone controls behave a bit differently with buffered signals than when they are allowed to interact with the impedance of a coil.

    For a tone control that is only in the circuit in passive mode, use this diagram:
  6. JP Morin

    JP Morin

    Mar 15, 2011
    the thumb pre already have a preamp bypass build-in. a "passive tone knob" would be useful but I'd use the fourth hole for something else... or plug it with a non used dummy knob or switch... May be a EMG afterburner in it, or a drive circuit ??