Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Just any old potentiometer?

Discussion in 'Luthier's Corner' started by bassman519, Jun 26, 2003.


  1. bassman519

    bassman519

    Jun 22, 2003
    Vermont
    I need to replace the potentiometers on my bass. I have 1 single coil pickup. Should I just get two 250k pots (one for my volume and one for tone)? Can I just go to Radio Shack and get some or do they need to be specifically for audio? Does anyone of a diagram of that mod for the vol. and tone to vol. capacitor thing?

    Thanks,
    Bassman519:bassist:
     
  2. Bass Kahuna

    Bass Kahuna

    Dec 3, 2002
    West Lafayette, Indiana
    Luthier, Custom Builder
    Most single coil passive pickups use a 250K potentiometer. I don't think Radio Shack carries that value of pot.

    If you want a 1 volume and 1 tone, then yes, you will need two 250K potentiometers.

    Stewart MacDonald has standard wiring diagrams at:

    http://www.stewmac.com/cgi-bin/haze...&s1=Free_info_sheets&ITEM=freeinfo/index.html

    You will also need to determine the value of the capacitor you will want to use. Stewmac sells them as well.

    :^)~
     
  3. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    the quality of the potentiometer can make a difference too. CTS are some of the best. Just get audio taper, and get them from a guitar parts supplier, and they should be alright. The ones from radioshack have a really long shaft that you have to cut to fit your needs. Just get some meant for guitar/bass use. They should be alright.
     
  4. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    Most local musical instrument stores will have them, too. The value of the pot will depend on the pickup, but most active pickups require 25k Audio taper and as Kahuna said, most passive bass pickups require 250k Audio taper.
     
  5. bassman519

    bassman519

    Jun 22, 2003
    Vermont
    I know this is going to sound stupid, but what does an active bass pickup do differently from a passive pickup? I've seen the wiring for them and noted the 9v battery but what does it do?


    Thanks,
    Bassman519:bassist:
     
  6. Bass Kahuna

    Bass Kahuna

    Dec 3, 2002
    West Lafayette, Indiana
    Luthier, Custom Builder
    Basically, there is a small preamp circuit built into an active pickup which requires a battery to power it. They usually also only require a 25K pot as they are low impedance.

    Also, for passive pickups, the 250K pots are usually used on single coil pickups, while for dual coil or "humbucking" a 500K pot is usually used.

    The higher the value of the pot, the more resistance between your signal and ground. For the tone pot, this can mean less highs are being sent to ground or "rolled off". In some instances, a 1 MEG pot (1,000 K) has been used for just this reason.

    :^)~
     
  7. Note that the pots don't affect the tone or volume in any way when they are full on for a passive circuit. And a cheap pot will sound exactly the same as an expensive pot (contrary to some claims by some hi-fi fanatics) The difference of course is that the cheap pot may soon start making crackle sounds when you turn it. Also, the value of the pot doesn't really make that much of a difference IMHO. So you turn it a tad more or less...whoopeee....