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Pot value question

Discussion in 'Pickups & Electronics [BG]' started by sprag, Mar 27, 2015.

  1. sprag


    Sep 15, 2011
    Melb Australia
    If I'm installing new pickups in my bass and a Bartolini NTMB preamp outboard from the bass do I need to alter the pot values for volume and tone to allow for there being two lots of volume and tone controls? if so, to what?

    Current specs:
    NTMB Bass, treble, mid pots are 50k linear
    Vol 25K audio and blend dual 250k 5a5c taper. (blend will be on the bass not the pre)

    Note: I want the bass to sound the same or as close as possible to having the above pots and bart preamp inside it.
    the intended setup on the bass thus far will be 2 x soap bar dual coil pickups, 2 x 4 way pickup selectors, 1 series parallel switch, vbt pots - values yet to be determined (could maybe skip the tone knob and get it all done on the outboard pre).

    I intend to use this outboard pre with a 250 k loaded p bass and whatever is in a standard Marcus Miller iv and musicman stingray 4h so I might need to alter things for those scenarios also but mainly interested in the above example.

    So, what say you?
  2. GoLeafsGo

    GoLeafsGo Not Quite Right! Supporting Member

    Oct 25, 2013
    Whitby Ontario
    Ohhhhh....never mind. Misleading title....
  3. rtav

    rtav Millionaire Stuntman, Half-Jackalope

    Dec 12, 2008
    Chicago, IL
    Start with this...

  4. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    So are you removing the pre from the bass and installing it in an outboard inclosure? Or installing another preamp in an outboard inclosure, while leaving the current Bart pre in the bass?

    If you are removing the preamp from the bass and want it to sound the same, you would have to install the same value pots in the outboard inclosure that are on the bass now, and run directly from your blend knob to the output of the bass. Though I don't understand why you want to do this.
  5. sprag


    Sep 15, 2011
    Melb Australia
    Removing existing mk1 pre from the bass replacing it with a NTMB preamp.
    I want it outboard so i can still have all available controls the pre offers with the addition of coil switching on the new pickups being installed and not have to get out the drill.

    I want it to sound the same so 1. when I find what pickup configuration I like, I may choose to install it in the bass and not change anything tonally.
    2. Bartolini gave them those values for a reason and that is probably what sounds best.

    The following is speculation only:- The blend control shouldn't matter as there will only be the 1 (onboard). If i forgo onboard tone controls they can remain the same values on the outboard. its just the volume control which is 25k… if two pots that add up to 25k are used would this make it the same, as the circuit would then see the same overall resistance?
  6. Usually 50 bucks for 1/8
  7. sprag


    Sep 15, 2011
    Melb Australia

    Not sure if I need more sleep cos it took longer than 5 seconds to get this or more Doritos cos… it took longer than 5 seconds to get this
    rtav likes this.

  8. You should note that changing resistances only results in a very slight change in tone. The values were more likely to have been chosen based on a combination of convention, and performance in regards to taper and adjustability, rather than tone.

    You need to be more specific on what you are planning to do. In what precise manner will you be configuring your scheme? It may be important to note that your 25k volume is placed after the buffering stage, so it has zero effect on the impedance of the pickup coils.
  9. sprag


    Sep 15, 2011
    Melb Australia
    If thats the case I'll just go with good ol' 250's. I know they get it done in my P and I have some lying around
    thanks L6M
  10. LoveThatBass


    Jun 28, 2004
    I put the single chip NTMB Bartolini in the bass in the icon photo on the left. My volume is a 250K as is then Blend. I used the Bartolini recommended pots for the Bass, Mid, and treble. On the mid I used pot/DPDT switch combo to select between 250hz and 800hz
  11. JustForSport


    Nov 17, 2011
    Stack the bass/treble pot(s) and there's no need for a drill.
    LoveThatBass likes this.
  12. ex-tension


    Jun 11, 2009
    Then don't use a volume pot on the bass. Wire the blend pot directly to the output jack. Use the existing volume pot on the preamp box.
    If you use a volume pot on the bass (which needs to be 250kΩ or 500kΩ after the blend pot) it's not going to be the exact configuration as when the preamp is inside the bass. But the difference on the sound is slight.

    Marcus IV and Stingray already have preamps onboard. You're not gonna benefit a lot from an outboard NTMB with those basses.
  13. sprag


    Sep 15, 2011
    Melb Australia
    I was thinking more of the Marcus which has passive mode. But thanks for the insight

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