Solving Bass Hum Problems (Grounding vs. Shielding)

Q: Why does my bass hum when I touch the strings and play in the rehearsal studio? I use SVT, Digitech multi-effects pedal and a Ibanez Roadstar II with big humbucking pickups.

A: There is some confusion out there between what happens when you have a grounding issue vs. when you have a shielding issue.

You have a grounding issue. Here’s how to tell:

  • If your bass hums once you touch the strings (but is otherwise quiet), you have a grounding issue.
  • If your instrument hums but becomes quiet once you touch the strings, you have a shielding issue.

For a ground issue, here is what I have learned from the researching vast the knowledge base of the internet:

All of the metal on your instrument should be connected, from the tuning pegs, through the strings, into your bridge, through the electronics, out the jack, through your instrument cable, into your amp and – eventually – through the ground of the outlet in the wall.

If you have a ground issue (and I’m assuming that it isn’t just bad wiring in your rehearsal space!), it is likely that a wire may have come loose or disconnected somewhere. I would take a look in the control cavity of the instrument and make sure that there isn’t a ground wire disconnected from the underside of a pot or the input jack.

You can also check under the bridge and make sure that there is indeed a ground wire connecting the bridge to the electronics ground in the control cavity.

If you have a multi-meter, you may be able to quickly suss out where the grounding issue is. If you’re scratching your head right now, you might take a quick peek and if you don’t see anything obviously wrong, take it to a repair person and tell him that you have a grounding issue. It should take them no time at all to find it.

For you other readers out there that may realize that you have a potential shielding issue. No Treble has a wonderful article on how to shield your bass.

Have a question for Damian Erskine? Send it to [email protected]. Check out Damian’s instructional books, Right Hand Drive and The Improviser’s Path.

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  1. I have a humming noise from a brand new Fender Jazz bass when I offset the front – back pickups dials, if I don’t have them even with each other my amp hums.
    I got a longer cord thinking I was too close to my amp but that didn’t work but what did work was tilting my bass in different directions the humming stopped . But every time I put the bass in playing position the humming started again ,so I simply keep both pickup dials in line with each other.

    Why would it do this?

    • I have this issue with all my passive basses. Whether they be a Jazz or one with a P/J set up. My understanding is that this is normal…Could be wrong though.

    • Brandon T.

      That is inherent to single coil pickups, like the ones in J-basses. Humbucking pickups usually have two coils per pickup to deal with 60 cycle hum. So, when you have both pickups on full the two pickups act as one humbucking pickup essentially. Depending on the wiring wherever you play gigs the hum that can be either more or less if you solo one of the pickups on your j-bass. I’ve played gigs where if soloed the bridge pickup and there was little to no 60 cycle hum, and other places where if didn’t keep both pickups on the 60 cycle hum would be so loud that it would just annoy the hell out of the soundman. The only solution if you would like to solo either pickup is to replace the single coil pickups with “stacked” humbuckers (humbucking pickups under a j-bass pickup cover)….or, another idea is get a noise gate pedal and adjusting the settings so that hum isn’t audible.

      • Brandon, thanks for your info. after purchasing this Fender Jazz bass I see a Fender bass with the humbucker pickups that’s not on the Fender website, it was at one time but I cant find it now and if I would have known I would have bought that particular bass. Although the one I have is nice the bridge is not made that great. I can move my strings around by just pushing on one side of the bridge , shouldn’t they be locked in.

  2. What about shielding? I’ve noticed that putting cable near strong magnetic field (like power cables, or near stage light) cause hum and sometimes even turning towards such source might cause it. Not mentioning using only one pickup in double J (like in jazz bass) setup while normally pickups should cancel each other. Are there any ways to additionally shield instrument? I’ve read somewhere about putting additional tin foil inside the body but are there any other “tricks”?

    • Brandon T.

      I had a similar issue with a Yamaha BB300 p-style bass. What I did to fix was to completely shield everything. It is preferred by many to use copper foil with conductive adhesive, but I was in a pinch and used tin foil (the tougher variety used for grilling because it tears less easily). I completely lined the control cavity (taking out the control pots first), the control cavity cover, and the pickup cavity (or both cavities if you have 2 pickups). You then need to connect the shielding in the pickup cavities to the shielding in the control cavity via a small gauged wire, and also connect the ground wire from the bridge to the shielding in the control cavity, too. Make sure there’s a just bit of foil slightly coming out control cavity to make contact with the control cavity cover’s shielding. When it was finished all the metal parts of the bass were connected and no more humming/noise (dead quiet).

  3. Fender bass’ have always been notorious for not shielding their products unless you paid the mega bucks for a ‘Custom Shop’ instrument. I have worked on several dozen for guitar and bass player’s that I’ve gigged with over my 46 years of playing. I unsolder everything in the control cavity and paint with shielding paint then do a thorough copper taping of the inside. Resolder and make sure of proper secure grounds(I’ve seen some come out of the factory that completely forget the ground that runs through the channel from the bridge to the control cavity, this sometimes may be your only problem). I myself own a 1968 Fender Jazz that I bought in 1969 when I started playing bass, it is the only bass I’ve ever owned and it is quiet, no hum, fret buzz, crackles or pop’s, whether moving around stage or getting up close and personal with an amp or mic stand. If you play learn the in’s and out of your instrument, it will save you tons in the long run and you feel more satisfied knowing you’ve can work on/fix it yourself.

    • There’s the perfect link/article/instruction above at the end of the article on how to do all this grounding/shielding . That’s why I love No Treble.

      • Fender has big bucks, why cant they make their basses like they should be made if they know this grounding/shielding is going to affect their product. I got little help from the people at Guitar Center when buying this new Fender bass and had to return the first one 3 times for inconsistencies with the product coming out of the box defected. So I had to do a update and finally got a nice bass, these guys could have told me buy a Yamaha instead. But they get angry at me for returning a bass 3 times that looked like a pawn bass not a new one.

        The very first bass I picked up when I was 18 in 1975 was a 1969 Fender P. Bass and it was awesome sounding , I said one day I will buy me a Fender bass, now at 59 I finally buy one . This Fender J. bass is pretty nice but the one I returned 3 times and had the manger order a new one 3 times was junk.
        I truly don’t get it ,

        • Hi Doc, are the Fender Bass’ you’re purchasing/returning American Standards or Made-in-Mexico? I bought my son a Red Squier P-bass from Fender and took it apart and re-soldered everything after shielding all the cavity’s, I replaced the bride with a heavier high density bridge and put a real ‘bone’ nut on it instead of the vinyl one they ship with. After setting the intonation and the action on it it was a very good beginner bass with better than average tone. Don’t feel bad about returning your gear if you’re not happy with it, I myself have a tendency to shy away from your ‘Big Box Chain type music stores’ they are all about making money and fall short on good customer service. There are some very good outlet’s online, if there are local mom and pop shops where you live check them out. I have done business with both as seller and buyer and haven’t had a bad experience yet. Don’t be afraid to buy used either. As stated before No Treble has lots of resources and reference material on their site another is Better Bass Gear, they are friendly on the phone and have everything you need for beginner to advanced DIY’fers. If Guitar Center wants your business bad enough they should take of you but no guarantees on that. Good luck, another good bass that I have personally bought as a back up is the Schecter Diamond-P Custom Active, priced right and very well built with plenty of tone to dial in.

          • Doc.Hoc.

            lewtenantdan , it was my own fault for not taking my time buying this new Fender bass, I rushed in to it and purchased the cheapest Fender J. bass Guitar Center had , made in Mexico.
            I just wish they would have talked to me about it , last December 22nd I bought this Fender bass and it was in the box when I got it home.

            This particular bass was $499 at the time , I took the first one back because it had a cracked pickup and scratched up pick guard and they ordered another.
            It came in the box and had scratched up tuning keys, then they ordered another, it came in the box and had a sap run that turned black under the clear natural wood finish across the bottom on the bass.

            Then around February 5th everything fell apart when I took the 3rd bass back. The only thing I could think to do is pay a little more and update and ended up buying this bass but its Lake Placid blue.

            I was made to feel guilty for taking back those 3 basses but the one I have now is okay, made in Mexico. I just wish I would have taken my time and bought a better bass like a Schecter , but things mushroomed and got out of control.
            I felt bad about taking those 3 basses back. It was my fault for not taking my time , I was just all stoked out about finally buying a nice bass and ended up making everyone angry at me , my old Ibanez needs rewiring.
            But this isn’t new , I seem to rube people the wrong way , it wasn’t my intentions to upset all those nice guys at Guitar Center ,making me feel like a outcast .
            I should have taken my time ,so I take the blame.

          • S

            Actually even Fender CS commonly lacks shielding, particularly on vintage RI’s as it is period correct to not use shielding (outside of brass plates.) Fender did not use conductive paint from Squier to Custom Shop until 2008. Even then, their shielding job is lacklustre at best. On a side note, your 68 P is susceptible to RF interference, which shielding addresses. You may have not experienced it anywhere but it is most definitely susceptible to hum.

            On a side note, the guide has one major flaw. You shouldn’t buy supplies from Stew-Mac. Their shielding supplies are low-grade but their prices are top-shelf. Use MG Chemicals Supershield for a better, more durable paint and source your copper tape off Ebay, just ensure you get double-sided conductivity (conductive adhesive.)

        • So why did you want a new one when there are so many beautiful old intsruments out there?

        • matt

          I hear that. Fender has gone downhill fast. I got a Geddy Lee Mexi jazz bass it cost me 900 bucks and ive had to put 500 bucks into it to make it stop humming. They really need to get thier shit together.

          • Lester S.

            Hum Debugger. Done.

          • S

            It costs $60 CDN in materials to shield a bass and that is including buying a $50 can of paint that will do over 10 basses. If you spent $500 to remove RF interference then you wasted a lot of money somewhere.

            If you are referring to spending a pile of cash on swapping the pickups, that was your choice. You bought a bass with single coils and expecting a totally hum-free operation, that is user-error. If you wanted humbuckers you should have bought a bass with humbuckers.