Do I have to live with this hum?

Discussion in 'Pickups & Electronics [BG]' started by frits51, Dec 8, 2012.

  1. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Posted this before, but I'm coming from a little different angle.

    MIM P bass - tone all the way to treble side, volume 100%, I get hum, enough that I don't like it. Very audible. Have to go about 60% of the way toward low side of tone to get rid of it.

    Yamaha RBX250 w/ P pickup configuration - same test, I get WAY less hum. I have to listen close to detect it.

    P bass - If I touch the metal volume knob or strings or bridge, hum stops. I have tested resistance between bridge, each string, jack nut and knobs and there is 0.2 ohms max (probably the test leads!). I seem to be grounded. Jack is new, cap is new Sprague orange drop 0.047uf.

    Neither bass is shielded. My cable path to the amp doesn't hum with any other instrument.

    Is this just a characteristic that's present to varying degrees with every bass that I have to live with? Is it possible to have a dead quiet passive bass with tone all the way to treble? Is there a 'most common reason' for this hum?

    The reason for the hum is surely still there when the tone control is all the way to the low side, but it's just filtered out.

    Grounding is stock, not 'star'. Pots aren't noisy. Solar storm is passed and problem persists.

    Next idea is to re-do grounds in a 'star' configuration unless somebody has a different idea.

  2. subdude67


    Jan 18, 2010
    if the hum disappears when you touch the strings or bridge it could be a ground problem so doing a star wiring job might help.

    is the hum present in any location you use the fender?
  3. KeithPas

    KeithPas Supporting Member

    May 16, 2000
    Sounds like a grounding problem.
  4. bumperbass


    Jun 19, 2012
    Is it a hum or a buzz?
    Star grounding won't help. That's recommended for different pieces of equipment, not within a piece of equipment.
  5. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas
    Just tried the same test with my son's MIJ Jazz. I have modded it with series/parallel switching, blend pot and star grounding.

    Yeah, there's a little bit of hum with tone all the way treble and volume 100%, especially with the bridge pup soloed... but not near as much as with my P. Of course, putting pups in series takes noise to zero, but my P pups are already in series.

    I may do star grounding on the P. If it helps some, I'll take it.
  6. frits51

    frits51 Supporting Member

    Apr 30, 2011
    Heath, Texas

    What's the difference between hum and buzz?
  7. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Buzz is the high pitched sound you are hearing. It's from electrical field interference. Hum is the low pitched noise you hear from single coils. That's caused by magnetic field interference.

    The P bass pickup is a humbucker, but because the pickup/bass is not shielded you hear that buzzing noise. Shielding can help that.

    You can also hear that kind of noise around light dimmers. That noise is very hard to get rid of. Shielding and hum canceling pickups help, but not totally.

    It can also be cause by bad grounds that the amp is plugged into.
  8. bumperbass


    Jun 19, 2012
    I find it very hard to imagine a P Bass with a hum issue if the bass is wired correctly. I played a few P Basses without a pickguard (so they really couldn't be shielded without a pickguard) and never heard a hum.
    SGD Lutherie is right. Put your bass near a fluorescent light and see if that's what you mean by 'hum'. Hum is just mostly low frequencies, close to a low B (around 60 Hz) or a middle B (around 120 Hz). Most likely, you're hearing 120 Hz with a hum problem. A buzz will sound just like the a 'bass honey bee' lol.
    If it's buzz, you need some shielding. I would also point out, you need to plug your amp into a known good receptacle. What happens when you plug in at someone else's house or a club?
  9. aprod

    aprod Supporting Member

    Mar 11, 2008
    I purchased a Boss NS-2 noise suppressor and it works great with my Strat. I have a 1970 P Bass and it never hums or buzzes.
  10. brotondo


    Feb 7, 2012
    Kimball MI
    My thunderbird's got a buzz that I'd reward handsomely to get rid of! shielding didn't do diddly squat. turning tone all way down helps some though. does your buzz change when you point you bass in different directions or lay it flat? I've given up, thrown it in a closet to rot!
  11. bassbenj


    Aug 11, 2009
    Hum goes away when you touch ground. Basses aren't shielded. Well, Duh! Yes, lack of shielding is THE most common cause of hum. Sure P-basses tend to be quiet because they are naturally humbucking, but that doesn't mean wires and other stuff won't pick up hum and noise.

    MY Squire P/J was totally unshielded and while it wasn't horrible there was some hum "that goes away" present. Fix was as always, copper foil shielding in all cavities and back of pickguard (people use aluminum foil on pickguards because it's easy and cheap, but I found it's better to just go whole hog and do it all in copper (unless the aluminum is already there, then I just leave it).

    The difference between basses has to do with just how "shielded" the unshielded wires are. Note that some basses use shielded wire to try to get away without the expense of shielding. While I'm sure this is better than normal wire, best is to just bite the bullet and shield the electronics. It's a common job with how-to instructions all over the net.

    You do NOT have to "live" with this kind of hum. And since a P-bass is naturally hum-bucking, you don't have to live with that kind of hum either!