Feedback from Jazz Bass

Discussion in 'Basses [BG]' started by Mosfed, Jan 27, 2014.


  1. Mosfed

    Mosfed The mighty mighty Supporting Member

    Joined:
    Apr 21, 2013
    Location:
    On the Mont Blanc
    Hello to all:

    A little background on my rig before posting the question. I use mainly Fender basses ('72 Jazz, '75 Precision, '13 Cabronita, '13 Road Worn Jazz bass and the odd duck SG bass) to a 1972 Ampeg SVT.

    Pedals include - a Boss OC-2, a Keeley Fuzz Head, a Moog MF-101 Envelope filter, a MXR Phase 90 reissue and a EHX Memory Boy.

    When I use my '72 Jazz bass, I find I can't have either pickup's volume anywhere close to max without creating ear splitting feedback. In general, with both guitar and bass, I like having my pickups dialed as hot as possible and then adjust volume and levels either on the amp or through pedals.

    On the '72, I have to back WAY off on the pickup volume and adjust in other places. The tone I get is different but basically fine.

    This only happens with the '72. It doesn't happen on any of my other basses.

    I had the bass checked through by my tech who couldn't find anything wrong. Now if I just need to play it as is, that is fine as I have an answer. But has anyone else had a similar issue? I would love to find a fix. As it is, if I switch basses during a session, I need to dial in a whole set of new settings.
     
  2. pfox14

    pfox14

    Joined:
    Dec 22, 2013
    Feedback from a bass is very unusual unless you have it facing right up in front of your amp, which I assume you're not doing. Have you tried another amp? Have you adjusted EQ settings to try and eliminate the feedback?
     
  3. Mosfed

    Mosfed The mighty mighty Supporting Member

    Joined:
    Apr 21, 2013
    Location:
    On the Mont Blanc
    Yeah man - I am with you - never really heard feedback from a bass before.

    The EQ doesn't really change much.

    I am absolutely baffled. Naturally my tech doesn't really bring it up to gig volume when he messes with it.
     
  4. Selta

    Selta

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    Feb 6, 2002
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    Somewhere Far Beyond
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    Just to clarify, if you just solo one pickup or the other, you still get the feedback? Or does it seem to happen with just one of them?
     
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  6. Mosfed

    Mosfed The mighty mighty Supporting Member

    Joined:
    Apr 21, 2013
    Location:
    On the Mont Blanc
    If either pickup (or both for that matter) are turned more than say 60% of the way up, I get ear splitting feedback.

    So yes - either on its own or both together and I get squeals galor!

    Thanks in advance for any advice.
     
  7. ux4484

    ux4484

    Joined:
    Apr 25, 2013
    I had a similar problem on my Fender JP-90, with my J pup.
    One or both of the pups might have gone microphonic.
    Turn down the volume to where the feedback stops, try this with each pup separately and together: Tap these places on your bass with your finger make notes on where the tapping comes through the amp: the pickguard (in a circular pattern), the bridge, and the pup cases, and lastly the pup poles.
    The only tapping that should come through the amp (even slightly), is on the selected pup's case/poles.
    If it comes through on the guard, it should be worse near the pup with the problem. If they are microphonic, you will hear an echoing thud through your amp, since it's a jazz bass (no switching) you then would have to isolate the pups from the controls to determine which pup. (Easy to do with a set of jumpers w/alligator clips with the control plate removed). If the pups DON'T have the problem clipped directly to the output jack, then one of your controls could be microphonic (rare, but possible). A microphonic pup needs to be repotted (covered elsewhere here on TB) or replaced. A bad control needs to be replaced.
    Both pups going microphonic simultaneously is a rare thing, though it can happen if your bass was in the sun in 90+ weather or if someone tried to adjust the pole pieces in the pups without heating them first.

    If any of these taps cause a static pop, it is likely a grounding/shielding issue. I've seen corroded or broken ground leads on a bridge cause all kinds of fun problems on guitars and basses. If you run your finger across the pickguard and hear a "Woosh" through the amp, your pickguard needs shielding (if not done already), and your grounding needs checking.
     
  8. Sollie7

    Sollie7 Supporting Member

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    Mar 13, 2011
    Location:
    Woodstock, Ga
    +1 yeah id check the ground to the bridge first
     
  9. Mosfed

    Mosfed The mighty mighty Supporting Member

    Joined:
    Apr 21, 2013
    Location:
    On the Mont Blanc
    Incredibly helpful! I will definitely go through what was suggested. Thanks so much

    If the pickup has gone microphonic potting would not be a big deal. Replacing would blow donkey nuts...
     

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