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Passive tone control with Active preamp?

Discussion in 'Pickups & Electronics [BG]' started by littlebooner, May 26, 2018.

  1. littlebooner


    Jan 27, 2012
    Kelowna, BC
    I’ve seen a few basses having active preamps along with a passive tone control and have heard people quite like it. I’m thinking of adding it to my bass with Aguilar DCBs and OBP-3 preamp.

    I have two questions/

    1. What are people’s thoughts with this control set up?

    2. How is a PTC wired in while having an active preamp?
  2. Snaxster


    Nov 29, 2008
    Hello. There is a fair amount discussion about 1. Search is you friend; but here is a recent thread with opinions for and against:

    Why bypass tone knob in active mode?

    And here are some search results related to 2:

    Search Results for Query: preamp passive tone | TalkBass.com
  3. Crater


    Oct 12, 2011
    Dallas, TX area
    Two options:
    1) If the tone control is placed before the preamp, you can use a standard 250 k Ohm pot and 0.047 mfd cap. This setup also allows the tone control to function if you can switch out the preamp.

    2) If the tone control is on the output of the preamp, you'll have to use a 25 k Ohm pot due to active preamps' lower output impedance. (I don't know what value of capacitor is appropriate)
  4. Well personally, I'm not into passive tone controls really at all. I only have one passive bass and it has a very different tone control. But this is a very popular mod. In fact there are lots of basses coming out that have this from the factory.

    You'll have to either drill a hole for your extra control, or stack two existing controls to free up a space.

    If your bass has an active-passive switch, you'll also have to decide whether you want the passive control on always, or only in passive mode. If you want it on always, it is simply a matter of wiring a standard A250K pot with the cap of your choice (47n or 100n are the most common for bass). If you want the PTC only to operate only in passive mode, you may have to re-wire your bypass switch. But if you want it on always, simply take a wire from the input of the volume.
    Passinwind likes this.

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