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Can these mods be done in my new preamp?

Discussion in 'Pickups & Electronics [BG]' started by ampegfuzz, Jan 11, 2014.


  1. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    I just picked up one of these pre amps and want to mod it.
    http://guitarfuel.com/SEB_Preamp_EQ_Harness.php

    [​IMG]

    i want to add:
    passive tone
    3 way pickup selector
    series parallel

    All into my 1979 Ibanez Musician

    [​IMG]

    the current preamp is GONE

    Can this all be done??
     
  2. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    Pics to help with adding passive tone to push pull pot, maybe?

    [​IMG]

    [​IMG]
     
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  4. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
  5. Sure.

    You can do that with any single input, non-PCB mount preamp.
     
  6. P Town

    P Town Guest

    Dec 7, 2011
    I see you have placed your electronics on a piece of synthetic carpet. I would recommend that you avoid this practice, due to the possibility of damaging the board by way of an inadvertent electrostatic discharge. Think about how you can develop enough of a static electric, (triboelectric) charge by walking across a carpeted floor, and touching any object that is at a lower potential, and sensing a "shock", (accompanied by a spark) when the charge on your body, and the charge on the object you come in contact with equalize. If the op amps have an FET input stage, they are very susceptible to this type of damage. You should really observe proper esd control practices when working on electronic equipment. Even components like metal film resistors can be damaged by an esd event.
     
  7. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    Where do I attach my lead from my tone pot on the volume pot? Middle lug?
     
  8. Wire it to the output of the blend pot.

    You're going to need to redo a lot of the wiring to get the series/parallel switch and pickup selector in.

    Also, I don't like the way the diagram shows the active/passive switch. It leaves the preamp input connected to the pickups in passive mode, and that causes a decrease in input impedance on the pickups, which loads them a bit.

    Do you need a new diagram for everything?
     
  9. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    I didn't do the S/P switch for now but it's in and running. I wired the tone pot up and took a alligator clip from the lead and touched all the points on the volume pot and no change. Could the tone pot ground out and not work?
     
  10. Sorry, wire it to the output of the blend pot, not the volume.
    At the volume pot, there is a decreased output impedance in active mode, which is why you hear no effect with standard value pots and capacitors.
     
  11. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    I figured it out. I didn't have the ground hooked up :)
     
  12. vxjoe

    vxjoe

    Sep 22, 2013
    Check G&L website for series- parallel schematic. Look for L-2000 bass.
     
  13. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    Can you make a bass microphonic with a preamp? I swear it wasn't microphonic before but don't remember :). Bass is just super noisy with the pre amp on. Microphonic in active and passive mode. Thinking it just raises the noise floor when it's on because of the microphonic properties. Thoughts?
     
  14. ampegfuzz

    ampegfuzz

    Feb 13, 2007
    Davenport, IA
    Welp I started from scratch and pulled the pre to hook up the series parallel switch. And the pups are a bit microphonic. Going to leave it passive since I think the S/P switch gave it the little bit of beef I was wanting from the active pre for. Going to go get new volume and tone pot and do that from scratch too and install the sprague orange cap I had extra laying around. Just need to decide 250k or 500k pots.
    [​IMG]
     



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