All of my basses seem to have grounding issues in some form or another—the hiss/hmmm that goes away when you touch the strings or bridge. my p-bass in particular has this issue. The cavity has the conductive paint in it and I have shielded the cavity with copper tape and have scuffed the back of the bridge. I have experimented with splaying out the ground cable under the bridge and twisting it. Nothing seems to work. I have tried different cables/different amps. Same problem. The problem is magnified if I add a pedal to the signal chain, which sometimes results in picking up radio frequencies. It happens in my computer/music room downstairs where I usually practice but also when I practice upstairs in my bedroom.
I do have transmission lines nearby, but they are 3 houses over.
i am in the midst of researching this as i want to shield my new bass, so my reply is not from experience but from my research…
that sounds like an interference issue, not a grounding issue (touching the strings makes the noise stop = interference, touching the strings makes the noise start = grounding issues)?
100% of the metal on the bass including all shielding needs to have electrical continuity with each other, this might be best sorted out by getting a cheap continuity tester or multimeter. its possible the tape does not have conductive adhesive or you have a big gap somewhere.
I have become something of a self-styled expert in that field.
An electronic buzz which stays constant regardless of instrument positioning, but goes away when you touch the strings, bridge, pots, or tuners could very well be a shielding problem.
That said, first thing I’d recommend is trying a different power cable, guitar cable, amp, and room. Eliminate the easy stuff first. If you do that and you still have a persistent buzz which stays constant with instrument positioning but goes away when you touch the strings, bridge, pots, or tuners, here’s what you can try, it’s worked for me in every situation where I have that:
Shield every pickup and electronics cavity on the bass. This can be done with conductive paint, or copper tape. If you use copper tape, make sure it has conductive adhesive, or that you shove a pin or something through overlapping layers to ensure that the copper connects through the adhesive. Make sure that the paint or tape on the electronics cavity extends past the lip of the cavity, so that it can connect with the pickup cover.
Shield the back of the pickup cover with copper tape that has conductive adhesive, or that you shove a pin or something through overlapping layers to ensure that the copper connects through the adhesive. Make sure it’s wide enough to connect with the shielding extending over the lip of the electronics cavity.
Connect the pickup cavity’s shielding to the electronics cavity shielding. I use screwed in wires for this, but I use conductive paint instead of copper tape. For tape, you can solder the wire to the tape.
Connect the electronics cavity’s shielding to ground. I use a screwed in wire for this, but again… paint instead of tape. For tape, you can solder it. To connect to ground, I’ve soldered the wire onto the pot where the other ground is at, and I’ve run the wire all the way to under the bridge.
Of course, scuffing the underside of the bridge is good. But if you don’t fully shield the cavities and get them connected to the ground, that won’t matter so much.
Again, assuming that shielding and grounding the shielding is your problem.
For whatever all this is worth.
Low End Lobster did a really good sort-of “how to” video on this for the Charvel San Dimas bass. It pretty much explains everything I do above, but with tape instead of paint:
Not all single coil pickups are created equal, some pick up more noise, some less.
Your enviornment plays a role, mixed with how well that noise is picked up by your pickup design. Dimmers, routers, flourescent lights, PC screens, motors, you name it.
Poor ground in your home electric system can contribute.
BUT - you can sheild all day long, and if your pickups are good at ‘picking up’, they will pickup noise.
Ground issues are different than interference issues.
Both create noise.
Ground issues can cause noise, but this is different from picking up enviornmental noise.
Fix the ground path issues, fix the ground noise, but not the enviornmental noise.
Shield things - reduce eniornmental noise, which may reduce it to where you can’t hear it, may not. Again - depends on the design and shielding of the pickup.
If you touch your strings and noise goes away, this is a grounding issue.
If you fix that issue, you still may have noise due to enviornment.
This does nothing if the top of the pickup is open to the enviornment (most cases). This shields the back of the cavity only, and is directional. Still open at the top to interference.
I think you are confusing pickup cover and electronics cover here.
What you want to do is sheild the pickup, not the cavity, and connect it back. This is only necessary if the pickup design is not sheilded. If pole pieces are exposed, you can tape the bottom of them and run a wire back to ground from that sheild tape.
No, he’s asking about a p-bass. The pickup cover is the electronics cover.
That said, on a bass that has a dedicated electronics cavity, yes, you would do the same on the electronics cavity.
Yet:
Now, in that video, Lobster does also put some tape on the pickups and wrap the spongy spacer thing:
I did forget to mention that. But the cavity should get shielded as well.
Honestly, John, I kind-of feel like you take issue with many of the posts I make about shielding and grounding. All I can say is that the exact procedure I documented above, with the exceptions on this post, is what has 100% fixed this issue for me on 6 or 7 basses.
I think that maybe we should just agree to disagree on some of this stuff.
One point he brings up is important - some pickups are just going to have noise issues regardless of what else you do. Single coil pickups are the worst for this, and it is magnified when they are unbalanced by another single coil.
In terms of noise potential, for which no amount of shielding will fix, I would say of the standard configurations it would be roughly (in deacreasing order of noise, noisiest to least noisy):
J-bass wired with pickups oriented the same way > P/J > J-bass wired with inverted pickups > humbuckers or P only.
Unless your J is wired weird, a P/J will pick up the most due to the single unbalanced J pickup.
Guitars get worse, with the many single coil pickup combos.
Obviously nonstandard pickups (i.e. hum-cancelling J’s, etc) aren’t accounted for there, and pickup noise potential varies greatly with pickup quality and other factors (number of windings, etc). And all pickups, even humbuckers, will leak some, it just may not be audible if you’re lucky. They are never perfectly offsetting.
I agree the grounding and earthing issues is not one and done. It’s like a sqeaky noise you find on a bike, it takes many, many troubleshooting to finally get to the bottom of it and usually the thing that work on one instrument may not work on the other every time that’s why the pajama boy covers everything from soup to nuts. He did not mention the one area that “Usually” plagues the bass, the bridge.
Most “assembles” gets too lazy to scrape the chrome off under the bridge where the grounding wire makes contact. This can be the last step you do. It’s funny how this is such a common problem when there’s only a few things in the electronic components. I feel like the companies got together with the shop and came up with this conspiracy.
Most of us experience “more than usual” noise @Old_WannaBe because we are all sitting / standing in front of / near our PCs emitting noisy, USB, , monitor, etc noise.
It does become a good way to judge bass design from a grounding/shielding perspective though.
you can’t do a Faraday cage on an instrument, because the pickups would need to be inside the cage (otherwise it’s not a Faraday cage), and it would prevent the pickups to pick up the magnetic field variations caused by the strings vibrations.
And while I’m in software now, that’s what I went to school for. I’m not talking out of my bunghole, here. I wouldn’t make a recommendation that I didn’t know worked based on my knowledge and experience.
I’m not citing him as an expert. It’s just a good video on shielding and grounding regardless.
thanks for responses but superconfused on some points
how do i connect the copper tape from the pickup cavity to the electronics cavity… there is just a tiny drill hole that the pickup wiring passes through.
not sure what you mean by pickup cover…its a standard P with exposed pole pieces
If you’re asking me, to clarify some of what I typed out hastily before, if you have a “standard” Fender-style p-bass like the ones I’ve shielded, you don’t have a separate pickup cavity and electronics cavity. They’re the same thing, all underneath the pickguard. Kinda like this:
So, what I’ve done is paint the entire cavity with conductive paint and go a little bit above the rim in the areas that the pickguard will cover. On the backside of the pickguard, use copper tape to shield the entire area that covers the cavity and meets up with the paint above the rim. Make sure the shielding is grounded; I screw a wire into the cavity floor and solder it to the pot where the ground is soldered. That will ensure that the shielding on the cavity is grounded, as is the shielding on the back of the pickguard by way of the contact around the rim.
Then ground the pole pieces of the pickups as shown in the images above and put it all back together.
