Wiring onboard preamp with no volume control?

Discussion in 'Pickups & Electronics [BG]' started by fourstringbliss, Feb 15, 2014.


  1. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    I'm thinking about installing a Bart NTMB preamp in my bass and want to skip the volume. I have four holes and want bass, mids, treble, and blend. I never touch my volume control anyway, so why have one?

    I'd be using an NTMB that comes without pots and using my own pots. How can I wire it without the volume? What do I do with the wires that are supposed to go to the volume control?
     
  2. ex-tension

    ex-tension

    Joined:
    Jun 11, 2009
    Messages:
    323
    The green wire connected to the volume pot is the preamp output. Connect that wire directly to the output jack.
     
  3. ctmullins

    ctmullins Registered thumper Supporting Member

    Joined:
    Apr 18, 2008
    Messages:
    2,236
    Location:
    MS Gulf Coast
    You might also consider using one push/pull as a mute switch.
     
  4. robd

    robd Supporting Member

    Joined:
    Mar 3, 2004
    Messages:
    1,181
    Location:
    just outside B-more Maryland
    My barts use a stacked knob for treble/bass controls. So volume, bass/treble, blend and mids only take up 4 holes.
     
  5. Register to disable this ad
  6. CrashClint

    CrashClint I Play Bass therefore I Am Gold Supporting Member

    Joined:
    Nov 15, 2005
    Messages:
    4,451
    Location:
    Wake Forest, NC
    You can get this from Aguilar for $20 so you can stack Bass/Treble.

    [​IMG]
     
  7. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    I'm okay without the volume. I have knobs I'm using that I really like and a stacked knob set would look out of place. The top on my bass is pretty thick as well, so I need to use long thread pots. Thanks for the suggestions, though!
     
  8. Technicality

    Technicality

    Joined:
    Feb 10, 2011
    Messages:
    55
    If you want the circuit to behave exactly as if there was a volume control there at full volume, get a resistor that is the same value as the potentiometer would be (for example if the potentiometer is a 25k, get a 25k resistor). Figure out which of the three wires that would connect to the pot joins up to ground, and connect that to one end of the resistor. Then connect both the other two wires to the other end. Any resistor will do, including the low wattage very cheap ones.

    If you are less bothered about how slight changes in the design might affect the sound, you can just connect the two non ground wires together though yes.
     
  9. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    That's aa great idea! I hadn't thought about the resistance of the pot even when full up. Would it make it brighter to leave the resistor out?
     
  10. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    Here's a pic of the volume part of the wiring diagram:

    [​IMG]

    You can see that there is one preamp wire going to the volume pot, and then the pot lugs either connect to the jack or to ground. How would I wire in the resistor in this case? We're only talking about a 25k resistor as well - is it worth the trouble?
     
  11. JustForSport

    JustForSport

    Joined:
    Nov 17, 2011
    Messages:
    1,668
    Just 25k is
    25,000 ohms,
    as opposed to 50,000 ohms
    or 500,000 ohms.
     
  12. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    Yup.
     
  13. khutch

    khutch Praise Harp Supporting Member

    Joined:
    Aug 20, 2011
    Messages:
    2,550
    Location:
    suburban Chicago
    Run the green wire directly to the output jack as someone said. Then connect the resistor between the lug on the jack where you connected the green wire and the ground lug on the jack. It may be a good idea to have a DC ground path on the output of the preamp so it is probably worth the effort. We would have to see the preamp schematic in order to say if it is necessary.
     
  14. fourstringbliss

    fourstringbliss Supporting Member

    Joined:
    Oct 5, 2003
    Messages:
    8,443
    Location:
    Puyallup, WA
    Here's the whole schematic:

    [​IMG]

    What do you think? Do I need to do the resistor? I'm not opposed to doing it - it's just a few more solder joints.
     
  15. ex-tension

    ex-tension

    Joined:
    Jun 11, 2009
    Messages:
    323

Share This Page