wiring diagrams to change blend pot to 2 volumes

Discussion in 'Pickups & Electronics [BG]' started by evic777, Dec 21, 2013.


  1. evic777

    evic777

    Joined:
    Jan 30, 2010
    Hello
    Help! LOL
    I have an NTMB918 Preamp. I want to remove blend pot and wire for 2 individual volumes and a master volume.
    Can anyone provide a basic diagram?
    I have one hot (yellow) wire that goes to my blend pot. I'm assuming I need to connect that to each volume pot???
    I just do not have enough knowledge to feel comfortable.
    Thanks!
  2. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    Pickup hots go to the wiper terminals, the first terminals are outputs, and the third terminals are to be grounded.
  3. evic777

    evic777

    Joined:
    Jan 30, 2010
    Thanks Line6man!
    Anyway you could send a brief diagram?

    Curious where the preamp wire fits in to this?

    Thanks!
  4. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    Disregard the capacitor, and wire the preamp's input to the "output jack tip terminal" connection in this diagram. Your jack wiring will not change.

    [​IMG]
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  6. evic777

    evic777

    Joined:
    Jan 30, 2010
    Exactly what I needed.
    Once again... Thank you and also... Merry Christams
  7. ex-tension

    ex-tension

    Joined:
    Jun 11, 2009
  8. evic777

    evic777

    Joined:
    Jan 30, 2010
    Exactly how do I do that? I have the preamp that you have in your link.
    And where do I attached the YELLOW wire from the preamp that was connected to the blend pot?
    Thanks!
  9. ex-tension

    ex-tension

    Joined:
    Jun 11, 2009
    Yellow wire is your preamp input. This is where you connect your pickups (via a blend pot or via 2 volume pots).

    Green wire is your preamp output. This needs to go to output jack.

    So, on the line6man's diagram, don't use the last pot and the wire going to that pot should be connected to the yellow wire.

    Then use the Bartolini diagram to wire your volume pot. You need a 25k pot for it (as you see on the diagram).

    For the individual pickup volume pots you can use 250k or 500k.
  10. JoeWPgh

    JoeWPgh

    Joined:
    Dec 21, 2012
    I can't believe how many still do not know about the wealth of wiring information at Guitarelectronics.com. While every possible variation might not be illustrated, there's more than enough info there to piece together what you're after. For the record, my only affiliation is as a customer, and a browser of their impressive library.
  11. evic777

    evic777

    Joined:
    Jan 30, 2010
    Line6man... After reading many posts until my eyes began to blur I think I am going to wait on adding a master volume and try the 2 individual pu volumes first
    The current volume pot in the bass is 25K
    Can I just add another 25K
    What recommendations for you have ... I value your opinion
    Thanks!
  12. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    Not unless you have active pickups. You can use 25k pots after preamps because preamps lower the output impedance. Before the preamp input, you have a higher impedance signal, and thus, you need to use 250k or 500k pots. The use of 25k pots before a preamp with high impedance passive pickups would load the pickups down and kill a lot of output.
  13. evic777

    evic777

    Joined:
    Jan 30, 2010
    To clarify... I have 2 bart humbuckers (99% sure they are passive) and NTMB918 pre
    I have two 25K pots... would you use them or replace with 250K ???
    Do I connect the YELLOW preamp wire to each volume pot where my each of my pu are connected???
    Will I be able to solo each pu?
    Once again... THANKS
  14. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Location:
    Brookfield, CT
    No, you connect it to 'output jack tip terminal' as explained in post 4.
  15. evic777

    evic777

    Joined:
    Jan 30, 2010
    oh... Obviously post 4 confused me a bit (easily done LOL)
    If I understand... If I am NOT installing a Master Volume I will not bridge the two volume together like the diagram shown above. Each volume pot will independently connect to the output tip along with the yellow preamp input. Correct?
  16. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Location:
    Brookfield, CT
    No, in that case you'll connect it to the left lug of the bridge pot as shown..... it would feed the master pot but you're omitting that. So in your case, the wire that's shown feeding the master (actually tone) pot is your yellow wire.
    The two volumes must be connected to each other as shown. The yellow wire connects to the second (bridge) pot. Thus the two pots act as a sort of mixer, sending the result down the yellow wire.
  17. evic777

    evic777

    Joined:
    Jan 30, 2010
    Dmusic148
    Finally got around to tackling this mod.
    I have everything wired as diagrammed.
    The yellow input to the NTMB918F preamp to the left lug of the bridge.
    The green out put from the preamp to the + tip of the output jack
    It works but the gain is significantly lower that before and when both pu are turned all the way off they still are very slightly on. ???
    I'm using 250K volume pots.
    Can you offer any suggestions?
    Thank you!
  18. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Location:
    Brookfield, CT
    Can you post a pic of what you've done? Please try to arrange the wires such that we can see what you've done .
  19. evic777

    evic777

    Joined:
    Jan 30, 2010
    Will do... I will post it in an hour or so

    Sent from my ALCATEL_one_touch_995S using TalkBass mobile app
  20. evic777

    evic777

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    Jan 30, 2010
    Hopefully this will post
    [​IMG]

    Attached Files:

  21. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    This points to improper grounding. There cannot be any other explanation for this behavior, because a properly wired pot reduces impedance to zero Ohms, which makes it impossible for any signal to pass through. Double check your grounding, and be sure there are no cold solder joints.

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