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preamp bypass retrofit?

Discussion in 'Pickups & Electronics [BG]' started by centralharbor, Dec 15, 2006.


  1. centralharbor

    centralharbor

    Nov 21, 2005
    hawaii
    I was wondering if it was feasible to put a preamp bypass (active/passive switch) onto my bass. I have an Ibanez sr400 and it has passive pups and a 3 band preamp. im not really knowledgeable in electronics; i could follow a schematic of a passive p or jazz and solder new pups into a bass, but that's about as far as i feel comfortable with.

    would this project encompass more than just cutting a few wires and soldering it onto a switch?
     
  2. tplyons

    tplyons

    Apr 6, 2003
    Madison, NJ
    What year is that bass?

    IIRC, they use active pickups, but don't quote me on it.
     
  3. centralharbor

    centralharbor

    Nov 21, 2005
    hawaii
    its an 01; the serial is c01xxxxxx
     
  4. NicJimBass

    NicJimBass Flossin'? I thought your name was Munson! Supporting Member

    Nov 22, 2004
    Lancaster, OH
    64 Audio · DR Strings · Source Audio · Hipshot
    Can you post a schematic or drawing of what the wiring looks like currently? Show where the wires are coming from and going, and what knobs do what, and I can probably tell you what to do.
     
  5. tplyons

    tplyons

    Apr 6, 2003
    Madison, NJ
    Same year as my SR400. I sold the preamp to a friend who somehow fried his and got rid of the pickups on eBay. If you don't like the preamp, get rid of the whole thing and go entirely passive.
     
  6. centralharbor

    centralharbor

    Nov 21, 2005
    hawaii
    Not too sure if I'm capable of doing this. If anything, I could take a pic of the control cavity.

    It's not that I want to go entirely passive, I just want to be able to shut it off every once in a while, mainly when I'm not really doing anything, but it's plugged in, so it doesn't drain the battery.
     
  7. Espidog

    Espidog

    May 19, 2006
    UK
    I'm not trying to rain on your parade here, but if you do go for the active/passive switch idea, there's one thing you should check first.

    I'm not familiar with the particular electronics of your bass, but if a pickup is designed from the start to be part of an active system, then its strength of output as a passive pickup is no longer an issue for the designer. Consequently, you may find that when your switch to passive mode, your pickups have a pathetically low output.

    Provided you feel equal to the soldering job, I would suggest that you unhook the pickups from the rest of the circuitry and audition them as passives before you decide to do all the modification work.
     
  8. centralharbor

    centralharbor

    Nov 21, 2005
    hawaii
    Good thought. Maybe I won't do this.
     
  9. 62bass

    62bass

    Apr 3, 2005
    You can get a decent tech to do the job for you and it shouldn't cost too much. You'll (or he will) have to select a switch, find a spot to instal it and wire it in, providing there's room for it in the cavity. The pickups have nothing to do with the switch which would be in the battery circuit.

    I've thought myself of doing that on some of my active basses just so I can leave them plugged in and be able to pick up the bass any time I want and play without having to fool around with the cord. But, I never get around to it and actually it's way down there on my list of things to do.

    If you want to get into switching out pickups or going passive that's another matter. I understand that bass sounds pretty good stock.
     
  10. The Penguin

    The Penguin duplicate account violation Banned

    Jun 21, 2006
    I'm not pelagic
    No, it's that simple. And you can make it disconnect the battery also.

    As already mentioned one issue you may run into is the pickups being low output, also you can get a loud pop when switching from active to passive. That can be fixed with a few resistors to control the spike but I can't tell you exactly where to put them. Here's a schematic using them but you're on your own for the science.

    http://bartolini.net/1_wirngs/ppapsw_i.htm

    Any electronics between the preamp and pickups will still work, volumes, passive blends, passive tones. Anything after will be gone in passive mode.
     

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