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Change Active to Passive?

Discussion in 'Pickups & Electronics [BG]' started by robd, Apr 13, 2004.

  1. I have a 2000 Modulus Q5 with Barts w/ an 18v preamp. (NTMB I think, the bass has 4 knobs, volume, p/u blend, mid freq, and stacked bass/treble)

    Someone in another forum said the p/u's on this bass were passive and just the preamp was active. So my question is can I just pull the preamp out and put in a couple of volume and tone pots in? Is it that easy? Or will the p/u not have enough output without the preamp?

    Or is there some way to wire it to be able to switch the pre amp on and off so it can be passive or active with the flip of a switch? Actually the pre amp turns off whenever the plug is pulled, so I guess what I want to be able to do is flip a switch and bypass the onboard pre amp if I want. Is this possible.

    Any help greatly appreciated.
  2. sdguyman


    Jan 31, 2003
    San Diego
    You can take the preamp out of the guitar and add the analog pots to the bass. I'm not sure about just adding a switch to the guitar to make it active/passive. I would go to the Bartolini website and look up their electronics. They sell them with an active/passive switch integrated within.
  3. Thanks for all the help, hope I'm not being too dense here but...if I just add the toggle switch what exactly does that do? Would the signal still have to go thru the active electronics to get to the output jack or would the toggle switch route it around directly to the output jack? If so I assume it would then bypass all tone controls and blend knob as well?? Or does it just bypass the boost section of the preamp? Would I be able to play the bass in bypass mode if the batteries went dead??

    I will take a look at the bart site tonite but I couldn't find a wiring diagram that matched my setup last time I looked, so I figured maybe the setup in the modulus was something specific to them and not standard Bart. Maybe I didn't look close enough...

    Thanks very much for all the responses.

    I guess the first thing I should do though is go home and pull on the volume knob and see if it pulls up. I've been playing passive pickups for 25 years and I never thought to check for a bypass switch.

  4. Just out of curiosity, say I added a bypass switch to an active Fender bass. Would it sound exactly like a passive Fender in passive mode? Or would there be some discrepancy in any way?
  5. No, I've found that the bypass switches work well, but not well enough to make the instrument sound totally passive when in bypass mode. But, that's just my 2 cents.
  6. David Wilson

    David Wilson Administrator Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    The most common setup for passive pickups/active electronics is that the bypass causes the signal to bypass the preamp entirely. In this case, the preamp is still working and still drawing power but isn't getting any signal. Think of the bypass switch as a router which decides to either send the signal to the preamp or just pass it straight on to the output jack.
    Unless you have an active buffered blend, which isn't common, your blend controls will still work. Blend knobs generally sit before the preamp in the signal chain, as it's the blended signal that has bass/treble etc applied to it.
    So if you have a signal chain such as:
    pickups->blend->preamp->master volume->tone->output
    Then the bypass switch effectively routes the signal straight from the blend output to the master volume.
  7. rubo


    Aug 25, 2003
    Robd, I'm in similar position as you. I have Elrick NJS-4 with Bart soap bars and NTMB. I just ordered a pair of Van Zandt Jazz passive pups. I'm trying to convert my bass to being completely passive. I'll probably have two volumes, two tones, one for pick up blend and one for parallel / series, so that will leave one knob useless. Well that's what I want - I don't even know if this type of configuration exist or possible to do. I'll contact some local tech guys once I get my pick ups. Of course I will try the VZ with NTMB first to see what kind of tone it will produce.

  8. Thanks again to all. I appreciate the input.

    The volume knob didn't pull up...that would have been too easy.

    "In this case, the preamp is still working and still drawing power but isn't getting any signal. "

    So does this mean that that if the battery is removed or goes dead then the bass is still not playable even when the preamp is bypassed? It would suck to play passive all the time and still have to put batteries in it.

    I guess I'll search the bart site and then head to the luthiers forum if I can't figure it out.
  9. David Wilson

    David Wilson Administrator Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    No, the signal doesn't touch the preamp in passive mode. If the preamp/battery is dead, you can still play in passive mode.

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