So your bass has a hum

Discussion in 'Pickups & Electronics [BG]' started by DiabolusInMusic, May 25, 2014.


  1. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Good day Talkbass.

    This guide is not meant as a slight on the already great guide on here, I have just found myself repeating the same post over 100 times so I figured I might as well make my own guide and link it from here on out. I am far from an electronics expert; I like to consider myself a shielding expert. I have shielded many basses from several major manufacturers and have yet to meet a bass I couldn't silence.

    This guide will only cover shielding, not soldering tips, wiring help or common sense (like soldering over a cloth, not your bass.) Please read the entire guide before trying anything and feel free to PM me with any questions you might have.

    I personally hate hum and would like to remove it from every bass I can. I learned a lot of what I know from here, so thanks for the help and sorry if I steal your tips and publish them here.


    A simple diagnosis can tell you if your bass has a shielding hum or a grounding hum:

    If your bass has a hum that goes away when you touch the strings/bridge/metal than you have a shielding issue. This guide will resolve the issue.

    If your bass has a hum that gets louder when you touch strings/metal/bridge you have a grounding issue. Please refer elsewhere for help on the issue, but I would check your ground connection under the bridge just for good measure.

    If your bass has a hum that remains constant regardless of touching metal/strings/bridge you have a deeper issue, although I would check the ground wire coming from the bridge in this case as well. It might be 60hz hum if you are using singles coils. Shielding does not address 60hz hum.

    Additionally, if your bass makes a popping sound when you touch metal/strings/bridge you are hearing static electricity discharging. Shielding will resolve the issue.

    As far as I know RF interference issues only arise with passive pickup basses. Just because your bass has a pre-amp does not mean it has active pickups. Some basses, such as the Musicman Stingray, are passive with an active pre-amp. I do not shield the battery cavity if it is separate from the control cavity on this style of bass and I have had success every time. I have never shielded a bass with a pre-amp in a separate cavity. I would think it requires shielding.



    This guide will follow my job on a Fender Standard Precision bass using conductive paint. You will need to solder at least one connection but you could get away with copper tape and no solder if you are not comfortable with soldering on this particular job(not recommended.) This job is extremely easy and the perfect time for somebody to learn how to solder. Solder will also stay permanently.

    As a person that has used aluminum tape, copper tape, and conductive paint, I prefer conductive paint for several reasons. Paint requires less effort and time, leaves a cleaner job, and it will not lose it's adhesion over time. Paint can also be put in much tighter spaces. I have experienced basses with such tight pickup routes tape would never fit and would just bunch up when the pickups were re-installed. All the fundamentals are the same regardless of shielding material used and pickup arrangement. If you are paying a pro to do this job demand they use conductive paint, if they don't take your work elsewhere. I would never pay for a copper tape job but that is just me.


    Supplies:
    1) Shielding material - I recommend conductive paint, copper tape, or aluminum tape (in that order.)
    2) Copper tape (if not being used as primary material.)
    3) 1 ground screw and eyelet, the smaller the better. If you need to get multiple wires on it, do not go too small but take the screw length into account. This can be done with copper foil instead if you do not want to screw into your body.
    4) Wire - you will need one wire per cavity. Optionally, you will need one wire for each pickup cover. As far as gauge, if it isn't hair-thin it should be fine.
    5) Painters tape if using conductive paint. TAKE NOTE OF WHAT TAPE IS SAFE FOR YOUR PARTICULAR BASS! I cannot stress this enough. If your bass is finished with poly it will be fine but nitro basses react to painters tape. Please take caution.


    Tools:
    1) Soldering Iron
    2) Screwdriver for ground screw
    3) Scissors/X-acto knife
    4) Tools to remove covers and access electronics
    5) Electrical tape may be required
    *)I highly recommend having acetone on hand if using conductive paint. POLY ONLY!! NOT AN OPTION FOR NITRO FINISHES!! Acetone will destroy a nitro finish.

    For the Jazz bass supplement please click here.

    For the Stingray supplement please click here.
     
    Last edited: Jun 4, 2014
  2. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Step 1) Access

    We need to access the electronic guts here.

    With painting I would recommend removing everything from the bass. If you are using copper/aluminum tape I would just remove the strings and pickups (and of course the guard and plate.)

    If you are removing the electronics from something more complicated and aren't good with electronics like myself, I recommend taping off all the wires so all you have to do is put them back. A P bass has everything attached to the pickguard, so it all comes off together. If you are doing a jazz bass you will have to de-solder all the connections to remove the pickups. If you have a vintage-style bass with brass plate/s in the cavity you will want to remove them prior to painting. You can tape over/onto them with success if you want, but removing them leaves a much cleaner job.

    You do not need to prep the body surface for any of these options but I do recommend giving the body a good cleaning to remove any debris. If it makes you feel better when painting don't do more than scuff the finish, but the paint will stick to poly and nitro without any prep work.

    1 bare body (Small).JPG


    Step 1*) - paint only step

    Tape your bass off everywhere! I cover everything, even the sides. You can end up spraying from all angles and the extra fifty cents in tape can salvage an entire paint job. Get the tape pressed down firmly. Sometimes when doing jazz basses I re-tape between each spray just to see if there is any bleedthrough onto the top. Better safe than sorry. Again, ensure that you can tape your finish and what type of tape is safe for it. I have used copper to shield a nitro bass only to remove the job over a year later with no ill effects on the finish, so you could probably use that but there has to be a better option. I do not know. My copper tape may not use the same adhesion as your tape, ensure this is safe on your particular bass with your particular tape!!

    A Fender Standard is done with polyurethane so it a durable finish that can take any kind of tape. It can also withstand acetone wipe downs to remove any excess conductive paint.

    You must remove any excess paint wet as it will not come off once dry. Period. The Goof Off graffiti remover you see in the picture is what I use to remove excess paint. I also like to wear a respirator and latex gloves when spraying.


    Step 2) Start shielding


    In this step we are going to line the control and pickup cavities with our shielding material. I like to bring my material up over the edge in certain spots ensuring the pickguard screws pierce the shielding on both the body and the guard. At least one or two screw holes is nice to cover if not more.

    Paint is nice and quick, spray it, let it dry (for 10-20 minutes) and spray again. I like to do three coats, but I go overboard with it. When doing nitro I like to spray the paint into a cup and brush it on. Ensure you spray the can out upside down once finished to prevent any particles from plugging the hole and wasting the can. I do not do the wire routing channels when shielding a jazz bass or similar style. I have found my basses are as silent as they are able to get without doing this step. If you are going to do shield the channels, it can be accomplished by spraying some paint into a cup and dipping pipe cleaners in them. Only surface routing needs to get shielding.

    If using copper foil it should always have conductive adhesive in my experience but you can always double check. You just need to tape the entire cavity, making sure to leave no gaps. Take care when cutting and laying your pieces. A professional looking job is quite hard to accomplish with copper as it can bunch up. That being said, nobody should ever see this work but you and your tech so I wouldn't stress the aesthetics.

    Aluminum foil works the same way but it usually lacks conductive adhesive, so you need to take that into account. In my experience it should work just as well as copper just ensure to overlap your pieces. Again, this is a little tricky to lay out a professional looking job.

    I have never tack soldered my shielding and it has never been required it to complete any job I have done, I wouldn't bother with it as it is a lot of added effort.

    Both copper and aluminum tape will be fine long term on poly finishes. As I said earlier, I have removed copper tape that was over a year old from a nitro bass with no ill effects but I have not used aluminum on nitro so I cannot speak for it's effects.

    2 Taped off (Small).JPG
     
    Last edited: Jun 3, 2014
  3. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Step 3) Shield Pickup Surrounds and Pickguard

    We need to shield the pickup covers and pickguard. If you have a metal control plate it does not require shielding but it needs to be connected to it.

    Remove the pickups from their covers and line them with shielding material. This is a perfect step to do while the paint dries. I prefer copper foil for this step as you can easily solder to it. Soldering a ground wire to the pickups is the ideal situation but some people are worried about melting their pickup covers, this guide will not be soldering this connection. You will note in the picture that after I lined the pickup cover I added another strip from the short ends on the inner walls around to the outer walls covering the screw hole. This way the screw pierces the copper foil and connects with the shielding in the cavity grounding it all.

    I also brought the shielding over the edge on the long ends so I could solder a wire to the outer edge of the cover, grounding the cover the aforementioned way. Don't bring it too high as you do not want the copper to be seen on the pickup cover above the guard.

    When I used aluminum foil I made skirts of foil folded over so it would remain conductive on both sides, these skirts would touch the shielding in the cavity grounding them covers. If your shielding might touch your pickups connections ensure you wrap electrical tape around the connections. Ensure the magnet holes are clear of foil.

    I have not shielded covers with conductive paint but it should would work.

    When it comes to pickguards just shield the areas that are over cavities, you do not need to foil an entire guard. I put tape over all any screw holes over the shielding to make a better connection.


    3 paint and covers (Small).JPG

    Step 4) Better ground wire connection

    This step is optional but recommended. I like to add a strip of copper under the bridge, covering a couple of screw holes. I like to solder the wire to the strip of foil. If doing this step, ensure that the ground wire and solder does not prevent the bridge from sitting flat on the body.

    I have also added copper foil over the screw holes for the pickups. This is not needed as there is some paint in the holes, but it will ensure a better connection between the cavity shielding and pickup shielding. Odds are you will have some little odd pieces left from shielding the covers anyways.


    4 copper body (Small).JPG
     
  4. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    5) Ground it all

    In this final step we will ground all our shielding.

    You will notice the red wire I have added. This wire connects from the eyelet attached to the ground screw to the common ground in the electronics. I like to solder the wire into the eyelet before I screw it into the body. Unsure of your ground point? Just follow the bridge wire and add it there (not the bridge side but that works too.) I have added mine to the common ground on the pot. People do not recommend soldering to pots as it can cook the pot. I am just not worried about a couple dollar part that has already lasted a decade. Do not use a ground screw longer than your body can handle! I recommend pilot drilling your ground screw hole.

    If you did the entire job in copper tape I would just solder the connection directly onto the copper shielding. It is fairly easy to solder to. Be careful not to overheat it as it will discolour and lose some of it's adhesion. You can screw through the tape if you prefer, but I personally wouldn't for fear of ripping the tape.

    If you do not want to put a screw into your body just take a piece of copper foil and stick it in the cavity, solder onto the foil and it will work just as well. The foil needs to have a conductive adhesive, so this trick does not work with aluminum foil.

    You can tape your connections down with copper foil tape but it is not an ideal solution and will probably fall off in the long term. I have done it for months before, but not really long term. I recommend learning to solder far more than this, but it is a fool's option if no iron is handy.

    If you were going to solder to your pickup covers now is the time to do it. My covers are being grounded by the screw piercing through the copper on the body and the covers. Each cover needs it's own wire or some means to connect the shielding.

    You will need to ground all cavities and pickup covers. You can check the connections with an ohm meter. You should have a resistance across all the shielding. The resistance should read close to zero. I usually find a 0.1-0.2 ohm resistance.


    5 Done (Small).JPG

    6) Re-Assemble and Enjoy

    Put it all back together and test. Your bass should now be quiet and you will guaranteed enjoy it more. Take care when putting the guard/plate back on that none of the electronics are touching the shielding. You will note my electronics were covered with electrical tape. My aftermarket guard doesn't fit my Fender as well as an ebay seller described.

    6 Completed (Small).JPG
     
    Last edited: Jun 5, 2014
    wistfulhum, Jefenator, Ron H and 8 others like this.
  5. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Troubleshooting

    If the issue persists double check all your connections. Start by soldering connections if you have not been soldering. Ensure all soldered connections are smooth and shiny.

    If you lack output after it all goes back together your shielding is grounding out your electronics. Ensure the wiring and shielding are not touching, check the pickup connections first. If you have a weird new hum, check your ground connection under the bridge.

    These are the only issues I have encountered.



    All in all this is a pretty easy job. This particular bass was my first shielding job and it was done extremely poorly. That was part of the reason I re-did the job. I took a picture so you could see how poorly this can be done and still work. I did the job with aluminum tape. I used folded over tape to make skirts for the covers. I honestly do not even know how the shielding was even grounded. This job worked fine for the last 4-5 years and never failed once. In my stupidity of youth I figured it would be smart to cut the aluminum tape off after installing the pickguard, as you can see in the pictures this was a bad idea and it left horrible scars. Do not cut on your bass.


    Old job (Small).JPG

    I did many basses with aluminum before I learned you can source copper foil tape locally from stained glass supply shops. It can also be sourced as slug and snail tape from some hardware stores. Do not buy the Stew-Mac stuff as it is highway robbery.

    Aluminum tape works but it is very difficult to solder onto, copper is quite easy to work with. Aluminum tape is used in ducting, it can found at any hardware store. I highly recommend not using aluminum tape but it may be all some have access to, and it does work just the same in the end.

    I buy my MG Chemicals Supershield conductive paint locally from B&E Electronics, they are a wholesale electronics parts seller. It runs about $40/can and a can does several basses. Your city should have something similar. It can apparently be purchased in brush on form.



    I think that is everything I know on the subject. Thanks for reading and feel free to ask me for help. I will be glad to assist in any way I can.


    :bassist:
     
    wistfulhum, Lillianna, Ron H and 11 others like this.
  6. Can you do a guide for a jazz bass? I feel like it might involve a tiny bit more work than a precision bass. Great guide!
     
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  7. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    I most definitely can.

    I will pop open one of my jazz basses and snap a pic so you can see one finished. I will have to find one to shield to make a fresh guide. It is essentially the same process except you will need to do one additional cavity (possibly two depending on your routing.)

    You shield the pickup cavities just the same and run a ground wire from each of the pickup cavities to the common ground back in the control cavity. You can run a separate wire to each pickup cover, but lately I have been using the copper foil trick to cut down on the wires used. (Putting foil over the cover screw holes causing the screw to complete my shielding.)

    With a jazz bass I try to not bring the pickup cavity shielding all the way to the top. I find it hides it a little better and functions just as well.

    I should also add I have never bothered shielding the wire cavities running between the control and bridge/pickup cavities.
     
    Sascha Erni likes this.
  8. I can also shield the pickguard near the pickup holes too right? I do remember my old American fender p bass had shielding on the pickguard so I assume its the same for a jazz bass.
     
  9. bluebird28

    bluebird28

    Feb 25, 2012
    Tacoma. WA
    Great Post I really appreciate the write-up. Thank you.
     
  10. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Correct.

    You have a Fender Standard Jazz if I recall, those have a "swimming pool" route under the guard. That whole route needs to get shielded and the guard covering the route needs to be shielded as well. It doesn't have to cover the whole guard, just the part over the route. On a higher end jazz basses, such as an American Standard, that route is not there so the pickguard doesn't actually require any shielding. I play my jazz basses without any pickguard and without any RF noise.

    Thank you Bluebird.
     
  11. gebass6

    gebass6 We're not all trying to play the same music. Supporting Member

    I have two Tune TWB63 basses.Exactly alike(except that one is fretless and made of Ovangkol.The other is fretted Walnut.But I digress).The fretted one has a buzz.The other doesn't.Both have soapbar humbuckers.Now,internally every thing LOOKS the same in both basses.So I shielded the electronics and pickup cavities(in the buzzy bass) with copper tape and put everything together.Now I still have a buzz,just from from the bridge pickup.It used to be both.I suspect that something changed when I put everything back together.The bridge ground is connected to the bridge but it's attached to a five pin bus connecter.(Small bus on the left.Is this normal?)

    Snapshot_2014531 (2).jpg

    This buzzing doesn't go away when I touch the strings,but it does decrease at a point when I rotate in a circle.Any advice would be appreciated.
     
    Last edited: Jun 1, 2014
  12. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Does anything happen to the buzz when you touch metal? Or does it remain completely constant? Does it happen in any other rooms? Are there fluorescent lights in the room? Does it get louder when pointing at the lights? Do the batteries in your pre-amp need changing?

    Is the shielding in the picture grounded? You mentioned the electronics being grounded, but not the shielding and I cannot see from that picture if one has been added.
     
  13. Bassist4Eris

    Bassist4Eris Frat-Pack Sympathizer

    This thread has "sticky" written all over it. Nice job, DiabolusInMusic!
     
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  14. gebass6

    gebass6 We're not all trying to play the same music. Supporting Member

    There is no change when I touch metal.It stays constant,but gets quieter if I face East and West.It happens in all rooms.Even when I use a Vox Amplug.Even outside!Turning fluorescent lights off doesn't make it go away,but it gets louder if I bring the bass REAL close.But that's expected.And the preamp batteries have been changed out recently.

    As far as grounding,I've heard two schools.1)That you don't have to have a soldered wire ground attached as long as the grounded metal components are touching the copper shielding.2)There must be a soldered wire ground attached to the basses wire ground.Regarding the latter I would have to know exactly where the ground wire terminal is to do so.Even so I tend to think it is grounded to the bridge by default.I.E.
    1.The bridge is connected to wire ground.

    2.Three of the bridge mounting screw tips enter the 9v battery cavity('bout .062).

    3.The copper shielding tape is punctured by the bridge screws.
     
    Last edited: Jun 1, 2014
  15. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    It does not sound like you have a shielding issue. If your issue was due to RF interference your body grounds the circuit and stops the buzz (my science might be wrong on that but my diagnosis is correct.) It still wouldn't hurt to ensure the shielding is grounded.

    If there are grounded components touching the shielding it is grounded no differently than if a wire was soldered to it. As long as that connection is made. Both those schools are the same thought. Your jack is not touching the shielding, if it was both the hot and the ground would be touching and there would no output from the bass. I do not know where else the shielding would be getting a ground from in that picture.

    Do you have an ohm meter? Test for resistance between the bridge and the shielding. If there is no resistance the shielding is not connected to the bridge ground.
     
  16. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
    Great job thanks .
     
  17. gebass6

    gebass6 We're not all trying to play the same music. Supporting Member

    I don't have an Ohm meter.I wouldn't know how to use it if I had one.At any rate,I will be taking the bass to the local guitar store repairman in the future.
     
  18. I've recently bought a second hand stingray, and it had a nasty buzz, which seemed to be affected by touching the bridge. Suspected the bridge ground was bad, checked, and it was (no continuity to ground). Lifted the bridge, the underside and wire were corroded. With a new connection, the buzz diminished significantly.

    There was still a tiny buzz though, which went away when I touched metal. I've already shielded the control cavity (then ran out of copper tape), should I do behind the pickup as well? Or is my problem with grounding?
     
  19. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Can you see any kind of physical connection from the ground to the shielding? I am not familiar with your bass but I am guessing it has a ground wire coming from the bridge. Assuming it does, just run a wire from that connection under the bridge into the cavity shielding instead of taking the ground from your control cavity. If that make sense.
     
  20. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism

    Your problem is most definitely a shielding issue if it goes away when you touch metal. I intend to pop open my Stingray when I open my jazz to take pictures so you can see the job in that as well.

    Here is an old post where I discuss shielding my Stingray. It is essentially the same process as the one you see in the guide.

    You need to shield any control and pickup cavities. A Stingray should have a metal control plate, that is already conductive, if it is plastic it needs shielding too. If you want to add some shielding to your guard you can but I don't think the Ray has surface routing so it is not needed (it has been a while since I have opened mine up.) You will also need to shield the pickup covers. Then you need to ground all the shielding.

    I hope that helps. I should have time to get pictures up this week.

    @Eris and Mjac thank you, I appreciate that.
     
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    Primary TB Assistant

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