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25K or 250K volume pot?

Discussion in 'Luthier's Corner' started by Smac61, Dec 19, 2002.


  1. Smac61

    Smac61

    Nov 24, 2002
    I've asked this on all the non-pro boards and usenet with no luck. Now I turn to the pros!

    I'm going to be installing a set of Bartolini 9J's in a MIM jazz along with an NTBT preamp. The 9J's call for a 250K control, and the preamp uses a 25K.

    If I wanted to do an active / passive switch, what value control should I use? What are the issues of using the 25K passive or the 250K active? Should I just skip it and consider it an active from here on out?

    Thanks,
    Sean
     
  2. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Use a 250K, just make sure it'san audio taper pot.
     
  3. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    The preamp changes the impedance of the audio signal. You match the pot with the impedance of the signal you will be tapering.

    Use a 250k pot, audio taper, before the signal hits the preamp/bypass switch. Basically, the pickups go to the blend pot, the blended signal goes to the 250k volume, that signal goes to the active/passive switch.
     
  4. Smac61

    Smac61

    Nov 24, 2002
    Ahhh, makes sense.
    The wiring diagram shows:
    pu's>250K blend>preamp>25K volume>output jack
    So I would go:
    pu's>250K blend>250K volume>preamp>jack if I read you right.
    No problems running the pre straight out to the jack?

    Thanks,
    Sean
     
  5. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    Bartolini has a wiring diagram for an active/passive switch on their site. It's pretty simple. The switch output goes directly to the jack. No problems running the preamp output direct to the jack. Your amp should sort out the differences between a passive and active signal.
     
  6. Smac61

    Smac61

    Nov 24, 2002
    Bartolinis site shows it wired pu's>blend>preamp>volume>jac so value would be different for passive vs. active.
    I took your advice and wired it pu's>blend>vol>preamp>jac with a 250K and modified Bartolinis diagram acordingly.
    All is well, sounds great both active and passive.
    Now if I could only decide how to dual batteries...

    Thanks and Happy New Year,
    Sean