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push/pull preamp bypass produces loud "pop"

Discussion in 'Pickups & Electronics [BG]' started by bino, Feb 17, 2006.

  1. bino


    Jun 27, 2002
    Orange County
    I've got a bass with an 18 volt Aguilar preamp installed by the luthier. When I engage the preamp I get a extremely loud "POP". Loud enough that I won't switch back and forth for fear of damaging my speaker.

    I've had several Laklands with the 9-volt bart preamp and this was never as noticeable a problem. You definitely heard something, but nothing of concern. Is this normal with the Aggie or can it be remedied?
  2. Edwcdc

    Edwcdc I call shotgun!

    Jul 21, 2003
    Columbia MD USA
    My Laklland 55-01 does this. I turn down the volume before I switch back to active. I don't have much need to switch during a song so it isn't a big deal.
  3. fookgub


    Jun 5, 2005
    Houston, TX
    An 'extremely loud' pop might be indicitive of a DC offest on your output. Amps are AC coupled, so they don't care, but it does mean your preamp is wired wrong. Take it back and make the guy fix it.
  4. klorence


    Nov 21, 2001
    Pittsburgh, PA
    I had this exact same problem with my Dingwall AB-II; 18v aggie 3-way.

    I wanted to keep dingwall's BluEQube cicuit in there, along w/the active-passive switch for the pre.

    Turned out that the popping would go away if a toggle was used for active/passive instead of a push-pull pot. But there wasn't any room in the cavity to add another toggle.

    Ends up that if a new type of push-pull switch that addresses this popping issue becomes available in the future, that would solve it.

    Turning the volume knob all the way down before pulling or pushing it "solved" the problem.

    It was only a pain in the a$$ the first couple of times I forgot to turn down first. Then it was not a problem at all.

    for what it's worth, hope this helps.
  5. You could try something like this:

  6. bino


    Jun 27, 2002
    Orange County
    hmmm. I seem to remember trying the volume down approach last night and still getting the "pop". I'll double check this evening before I call the shop to see what's what. Can't imagine the guys missing it. It's as plain as day.
  7. klorence


    Nov 21, 2001
    Pittsburgh, PA
    could be a different issue then, with your pre setup.

    with the particular electronics setup i had in the dingwall, turning down solved the pop.

    good luck!
  8. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    I'm thinking it's a DC offset, too.

    Is the output of the preamp capacitor coupled? If so, a bleed resistor--maybe a half megohm or higher--will help pull it to ground.