Passive bass hum

Discussion in 'Pickups & Electronics [BG]' started by frits51, Jul 26, 2013.

  1. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Just bought a Yamaha BB414 passive, PJ configuration, V-T with pup select/blend switch.

    It's got a hum. Controls don't affect it. Touching strings, bridge, jack doesn't affect it. Wiring cavity is FULL of LONG wires! Many could be shortened.

    Cable and amp are noiseless with my other passive bass.

    I'm thinking this may be my initiation into shielding that I have been trying to avoid for a long time.

    Unless you have another solution!

  2. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    I shielded the bridge pickup only. The 'P' neck pickup is dead quiet.

    No change really. Bridge PU soloed is still noisy. Mixed with neck PU... not so noisy. Noise is more severe with tone rolled forward, goes up and down with volume (contrary to original post).

    Touching strings, bridge, etc. has no effect. I'm wondering if the bridge PU is what it is and the noise will be with me until I change the bass or the pickup.
  3. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Forgot to mention... standing in front of the amp, the orientation of the bass to the amp has a big effect on the loudness of the hum. I hadn't noticed that before.
  4. WoodyG3


    May 6, 2003
    Colorado, USA
    If touching the strings doesn't help, the first thing I would check is your bridge ground connection.
  5. uOpt


    Jul 21, 2008
    Boston, MA, USA
    You say the P pickup is OK but the single coil is not.

    You know that shielding only helps against electrostatic but not electromagnetic interference? That means if you have strong sources of electromagnetic interference you won't get rid of it short of real hum canceling. Would you say that a large part of the noise is 50/60 Hz cycle hum and other strong "individual" sounds, as opposed to more random buzzing possibly mixed in with radio?

    P.S. I would be careful with so brutal shielding on the back of a single coil. It doesn't do anything about electromagnetic interference but it has eddie currents that can dampen the single coil quite a bit. I can't tell you whether it's audible to you or not, just saying don't tape it up without doing before/after soundclips.
  6. This isn't the only case where there is a slight hum. I have played one that also had it and even in videos from youtube you will find it present.
    It might not make sense but check the connection on the volume and tone pots instead of the bridge ground.
  7. Rune Bivrin

    Rune Bivrin Supporting Member

    Oct 2, 2006
    Huddinge, Sweden
    Well, there you go!

    A regular J pickup is a single coil. Single coils pick up magnetic fields. Your amp puts out a fairly strong magnetic field from the power transformer, and the alignment of the pickup to that field will determine how much of it gets inside the coil of you pickup.

    You can basically only do something about this by either:
    • Change pickup
    • Add a reverse wired coil in series or parallel with the pickup
    • Change amp
    • Move the amp to another room
    • Shield the amp with a thick steel box
    • Get a hum killer pedal
    • Find the best possible position and stay there
    • Don't use the bridge pickup

    My band had a practice space which was very close to some kind of big transformer, and I had to change pickup on my Aria Pro to make it bearable.
  8. I have an active Yamaha 5 string bass. Every so often it gets a nasty 60 hz hum (a 'b' note hum). I purchased the ElectroHarmonix Hum Debugger. Click on that, hum goes away and leaves your tone. For me, $120 well spent.
  9. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    I would bet its just 60hz hum. A split or stacked coil Jazz pickup will most likely fix it.
  10. iiipopes

    iiipopes Supporting Member

    May 4, 2009
  11. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Thanks for the ideas.

    I just got the bass. We're going to try it as-is, see how it works for us where we play.

    I expect we'll be using neck and neck/bridge mix but not soloing bridge pickup (although that would be a giant waste of some great tone!).

    I really don't want a hum-killer pedal and another 9v battery... but it could happen.

    We'll see. Thanks again!
  12. bassbenj


    Aug 11, 2009
    Then it's obvious. Your bridge pickup is single coil and what you've got is single coil hum. Shielding will do nothing for that.

    1. Hum that goes away or gets less when you touch strings is due to need for shielding.

    2. Hum that does NOT change with touching strings or ground but DOES change with bass orientation is single coil hum, only fixed by going to hum-cancelling pickup.
  13. bassbenj


    Aug 11, 2009
    Yes, it's a conundrum. My P/J has a Dimarzio J bridge PU I put in it which is hum cancelling just for this problem. But single coil tone is the shiznit. So there you go. Rock and hard place.
  14. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Thanks, bassbenj.

    I have a lot to learn. Thanks for being willing to teach.

    The bridge PU in this Yamaha BB414 is not a J form factor. Very different. Not sure what replacement options there might be.

    Thanks again!
  15. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Also, I've got a Yamaha RBX1000 with PJ configuration that I'm re-building with Bart NTMB pre and Bill Lawrence P46 and J45 pickups. From what I've read, I don't expect to have this noise problem with this bass.

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