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Question re: MIM Jazz + Bartolini wiring

Discussion in 'Pickups & Electronics [BG]' started by FunkyD, Jun 10, 2011.


  1. FunkyD

    FunkyD Supporting Member

    Mar 16, 2011
    NJ, USA
    Hi everyone and thanks in advance for your time and feedback. I've scoured the archives and don't see my question already answered.

    I have a ~2000 MIM Jazz bass and I'm in the process of replacing the OEM passive PUs and replacing them with the Bartolini 2-way preamp NTBT-918 and Bartolini PUs. A single battery compartment has been routed out of the back of the body and a wire access channel has been drilled so I'm good there. I will be shielding all the cavities with copper tape. I can decipher a basic schematic and handle a soldering iron so I will complete the electronics installation myself, but I've run into some questions after viewing the Bart schematic shown below.

    1) The schematic shows 4 externally accessible pots labeled A-D. I interpret this to mean that if I want to configure things as shown I will need to move the output jack to the side of the body so that the four holes in the control plate will accommodate the four pots. I would like the guitar cable off on the side of the guitar but really don't want to carve up the body any more - the battery compartment routing was successful and I don't want to push my luck, so perhaps I can combine bass and treble controls by using a concentric pot?

    2) There is also a gain trim pot labeled E in the schematic. This appears to be "set it and forget it" in that it should be stored inside the body cavity. Is there any reason I'd want this to be accessible from outside the cavity, and if so, can it be replaced with a more common panel-mounted pot? Assuming yes, would it be possible to use a concentric pot here as well, perhaps partnering with the volume pot?

    I suppose the best-case scenario, if possible, would be to keep the output jack mounted on the control plate and use three concentric pots (volume/gain, bass/treble, neck/bridge PU blend).

    3) Is there any reason I might want to consider switching between active/passive, and if so, am I correct in assuming it's as simple as adding a small toggle switch somewhere in the circuitry?

    Again, I appreciate any suggestions/advice/experiences you all might be willing to share.

    Thanks,

    D
     

    Attached Files:

  2. Rano Bass

    Rano Bass

    Sep 9, 2006
    Tijuana Mex.
    Answers:

    1) Yes, you can use a concentric 50k pot for bass/treble.

    2) That is a set and forget case, is used just to match the output of the bass with other basses you might have.

    3) That depends of what you want, to me it is not that important because i want the preamp all the time.

    One thing i would recommend is that you use a vol/vol configuration instead of the blend knob. The blend pot is deeper then the volume knob and the preamp would be squeezed below the blend.
     
  3. FunkyD

    FunkyD Supporting Member

    Mar 16, 2011
    NJ, USA
    Hey Rano:

    Thanks so much for the reply, it was very helpful.

    I'm not sure it matters but since my original post I've discovered that I incorrectly referred to "concentric" pots when I should have said "dual" or "stacked". I think you probably understood what I meant however.

    I was able to pop into an electronics shop earlier today and the folks there were also very helpful. They immediately understood what I'm trying to accomplish here - including the use of vol/vol instead of the blend - and know exactly what parts I need. I should have everything in my hands early next week.

    Thanks again.
     
  4. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Concentric and dual are not always the same thing. Some dual or stacked pots have both decks turning with the one shaft, such as with a blend control.

    Concentric pots have concentric shafts, with one inside the other.

    You also want one with center detents.

    So you need this part:

    Potentiometers - Pots | Jacks | Switches | Shielding

    Go down to where it says:

    "Stacked EQ Pot- $18 (50K w/center detente - for active systems)"

    That would replace the tone control on the Jazz plate. Then you can do two volumes or a volume and blend. I prefer volume/blends, but either one will work.
     
  5. Rano Bass

    Rano Bass

    Sep 9, 2006
    Tijuana Mex.
    Cool!

    Let us know how that project turns out.
     
  6. FunkyD

    FunkyD Supporting Member

    Mar 16, 2011
    NJ, USA
    Thank you also David. I'll keep that link in mind but first I'm holding out to find something with a lower profile, although I'm finding it extremely difficult.

    Thanks again,

    D
     
  7. kb9wyz

    kb9wyz

    Sep 8, 2008
    Bloomingdale,IL
    Not to be thorn in anybody's side, but every time I have seen a Bartolini pre, the freaking knobs run in reverse. That is to say that clockwise is down, widdershins is up. I thought it was just my bass, because it's lefty, but all the righty's I've seen are the same way. NOTE: These were all Ibanez basses.

    So, long story short, is this how all Bartolini preamps are setup? If so, should dude get left-handed pot so he doesn't have one oddball control?

    Just thinking out loud.
     
  8. FunkyD

    FunkyD Supporting Member

    Mar 16, 2011
    NJ, USA
    Thanks for the post kb.

    Wow, this just seems to get more complex instead of more clear. I'm already having such a hard time getting through this "simple" mod and now there may be something else to consider. I can tell you that sometime around 1994 I purchased a brand new Pedulla MVP with an active Bartolini P/J configuration and the pots ran clockwise...I think I'll worry about this if and when it presents itself.

    D
     
  9. kb9wyz

    kb9wyz

    Sep 8, 2008
    Bloomingdale,IL
    Maybe it's just Ibanez, then. I have seen a few goofy things that have left me scratching my head. I guess a good look a the schematics and a quick email to Bartolini would be the easiest solution.

    Some people think that counterclockwise should be down. This happens on a lot of lefty basses. I can't explain Ibanez, though.

    Fun story: The bass I just rewired had the pots set to reverse. This is because making the bass lefty means that the player lives in bizarroland. :D The fun part of the story, you ask. The pots were standard, right-handed audio taper.
     

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