Is shielding required on a passive P-bass?

[Koshchei]

Source?

Observation from having used both methods. Next to a noisy transformer or other source, conductive paint seems to let more EM noise through than copper tape at the same distance. Note: They cost about the same on Amazon for enough material to do several instruments (less than $20).

 

[BlueTalon]

Source?

A continuous sheet of copper is going to be conductive. A conductive paint, which depends on suspended conductive particles suspended for its conduction, isn't necessarily going to be as conductive.

 

[Rolling Thunder]

No multimeter. Wouldn't know how to use it!

It's not rocket surgery. A multimeter has a red and black lead with metal tipped pointers. Continuity means that charge is going from point A to point B. Imagine a wire not connected to anything. Put one lead on one end and one lead on the other end. Your multimeter will beep which indicates continuity (when it's set to "continuity" mode). Now cut that wire in half and do the same thing...see where I'm going?

 

[Kro]

A continuous sheet of copper is going to be conductive. A conductive paint, which depends on suspended conductive particles suspended for its conduction, isn't necessarily going to be as conductive.

I can't say I agree, especially to the extent that it's needed for shielding. After multiple coats the paint seems to conduct without issue, and doesn't have the downside of deteriorating adhesive.

Testing continuity I haven't seen any issues with the paint I've used. YMMV, but objectively I don't think it can be said copper tape is superior in this application.

 

[EatS1stBassist]

This is my preferred method and source. Just line the cavities with it, make sure your bridge is grounded (you can solder the bridge ground directly to it) and that the shielding is connected to the circuit ground, and you're set. Don't forget to line the back side of your pick guard over the cavity opening, and make sure the tape comes over the edge of the cavity a little bit to make contact with the pick guard.

Copper Foil Shielding Tape w/ Conductive Adhesive Guitar Bass 3/4" x 18' roll | eBay

By the way, a multimeter would be a worthy investment. You should be able to get one for around $20 or so. You would use it to check continuity, among other things. For example, you could tell immediately if your bridge is grounded or not by touching one of the leads to your bridge and the other to the visible portion of your jack -- it should show zero resistance or something close to zero. If the reading jumps to a much higher number, you know you have a problem. Plus, you could measure your pickups with it.

Good info! BT!

 

[Bassamatic]

I buy the 2" copper foil from StewMac. It is the most cost effective because you can cut it to any smaller size as needed, and you will have less seams or joints.
P Pickups are the most genius hum cancelling pickups out there, but the wiring MAY pickup some EMI from AC power nearby or other gear such as light dimmers or some wireless transmitters. Adding the foil is cheap and easy and WILL prevent nearly all hum pickup. Just be sure everything is grounded. Meanwhile, if you are not experiencing any issues, you don't have to make it a priority.

I I REALLY want to do it right, I do a star ground to the foil - ALL the grounds go to one place. Necessary? Maybe not - but it is the RIGHT way.

 

[BAG]

Firstly, the presence of that screw into the cavity suggests that the shielding paint is under the green. You don't need a full multimeter, just a continuity tester and you can probably get one from your local electronics shop for under $10. It will just beep if there is continuity between two parts. The problem you have is that to properly check if the cavity is shielded you'll need to scrape a bit of paint off..... without scraping so much it goes through the shielding paint.... and you really won't know how well they painted the shielding.

If you're not hearing any noise then you might not have to do it anyway but there is always the chance that you plug in at a gig or rehearsal somewhere and get some noise however with a Pbass it will generally not be too bad.

In saying that, I have done a shielding job on my Pbass as the last two places I lived had horribly noisy environments and while the noise from the Pbass wasn't much, it is now zero. It's not a difficult job with the copper tape that has conductive adhesive. I even shield the pick guard....not entirely, but over the pickup and control cavity as well.

 

[ToneMonkey]

This is my preferred method and source. Just line the cavities with it, make sure your bridge is grounded (you can solder the bridge ground directly to it) and that the shielding is connected to the circuit ground, and you're set. Don't forget to line the back side of your pick guard over the cavity opening, and make sure the tape comes over the edge of the cavity a little bit to make contact with the pick guard.

Copper Foil Shielding Tape w/ Conductive Adhesive Guitar Bass 3/4" x 18' roll | eBay

By the way, a multimeter would be a worthy investment. You should be able to get one for around $20 or so. You would use it to check continuity, among other things. For example, you could tell immediately if your bridge is grounded or not by touching one of the leads to your bridge and the other to the visible portion of your jack -- it should show zero resistance or something close to zero. If the reading jumps to a much higher number, you know you have a problem. Plus, you could measure your pickups with it.

Harbor Freight has a multimeter for around $5.

 

[N. Kentucky Bass]

I’m not hearing any noise or buzzing. But I may get some tape and give it a go. I wrote to Fender and asked about the paint over. Will report their response.

 

[byacey]

P bass are pretty forgiving of noise. I have a P with Wilde P46 pickups, and they are dead quiet everywhere.
I twisted the signal lines, but no shielding.

 

[fourstringdrums]

I had to copper foil shield my Serek. Most p-basses I've had have required it in a few different places that I've lived.

 

[BlueTalon]

I buy the 2" copper foil from StewMac. It is the most cost effective because you can cut it to any smaller size as needed, and you will have less seams or joints...

I I REALLY want to do it right, I do a star ground to the foil - ALL the grounds go to one place. Necessary? Maybe not - but it is the RIGHT way.

I prefer using 1/2" or 10mm tape. Seems & joints are a non-issue with conductive adhesive, and it's a helluva lot easier to cut bits of it to length and use that than cut narrow bits off of 2" tape. It may take a little less time to shield the broad flat areas, but how many broad flat areas are there in a bass cavity? The little bit of time saved with wider tape on broad flat areas is more than made up for by reduced pain-in-the-ass in the smaller tighter areas.

A star ground is pretty much meaningless on a passive bass. The entire cavity shield is the center of the star -- if you ground the bridge at one point on the shield and the pots at a different point, it's still the same ground. It would be like connecting at two different points of the same wire. Electronically, it's the same. You can do a star ground if you want to, of course, but you don't gain anything by doing it.

 

[BlueTalon]

I can't say I agree, especially to the extent that it's needed for shielding. After multiple coats the paint seems to conduct without issue, and doesn't have the downside of deteriorating adhesive.

Testing continuity I haven't seen any issues with the paint I've used. YMMV, but objectively I don't think it can be said copper tape is superior in this application.

You're not going to see the difference by testing for continuity, you're going to see it by testing for resistance.

 

[Andy Daventry]

Everyone should have a multimeter. They are easy to use and come with a sheet of instructions.

Now, I am not an electronics expert, and I'm saying this in the sure knowledge that one of the experts here will correct me if I'm wrong, but I understand that if your guitar is already shielded under the body paint, then adding a further layer of tape - a second shield - could, if both shields are grounded, lead to capacitance issues which could affect the sound.

Does anyone know if this is actually true?

 

[Gilmourisgod]

Ive tried both paint and foil. The paint has to be thoroughly mixed to work, it dries literally as you apply it, so it tends to clump, and usually requires two coats, so i tend to use it in places that would be a PITA to do with foil. The little bottles you see on line are barely enough to do one or maybe two guitars, which makes it a bit expensive for what you get. They make spray cans too, which probably does a more even coat. The conductive adhesive foil is pretty idiot proof, and works better on big flat surfaces like the back of a pickguard. Ditto on the Harbor Freight multimeter, perfectly serviceable continuity check and simple resistance readings, and dirt cheap at $6.79, or less with a coupon.
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[Kro]

You're not going to see the difference by testing for continuity, you're going to see it by testing for resistance.

You're going to see the difference yes - I'm just arguing if it's something that is meaningful or not in this application. I'd argue that the difference in resistance doesn't tell you much of anything in terms of how effective the shielding job is (between say, paint and foil). Happy to be corrected.

 

[Killens84]

I bought an American Pro P bass last year, and installed a Lollar pickup. The bass was a little noisier than I liked, especially if I wasn’t touching anything metal on the bass, so I shielded the whole cavity with copper tape (from Amazon). If there is shielding paint under the top coat of paint, it wasn’t doing its job 100%. Since that one particular ground wire was already screwed into the body, it was easy to ground the foil. It made the bass 100% noise-free... Works perfectly! As you can see, I ran a little bit of the foil over the edges, in order to make contact with the pickguard’s foil.

 

[40Hz]

It won't hurt, and if you're uncertain about whether it's already shielded, conductive copper tape is more effective than conductive paint.

When a sufficient number of coats of a correctly formulated shielding paint are properly applied, it works every bit as effectively as copper foil.

Problems occur when it’s a cheap formulation you’re using, or you don’t provide sufficient coverage. Most reputable formulations recommend at least two and preferably three evenly applied coats.

Just make sure to get the underside of the pickguard as well to properly enclose the Faraday Cage you're constructing.

You’re not really constructing a Faraday cage. A Faraday cage needs to be completely electrically enclosed. No openings or gaps at all. Think wire box. The shielding on a guitar or bass doesn’t meet that criteria.

While all passive pickups, are grounded, many aren’t shielded at all. The standard Fender style PB splits and JB single coils have no shielding. So bye-bye Faraday cage. The Tele beck pickup is shielded. But the bridge isn’t. Nor are any of your regular Strat pickups.

If you really want a Farady cage you’ll need to get a few rolls of shielding mesh, build yourself a box, completely shield the box, and play your bass inside of that.

Fortunately, we don’t need to go to that extreme to get a virtually noise-free bass. “Pretty good” shielding is good enough.

 

[40Hz]

Minor note.

You probably won’t ever want to apply copper foil over shielding paint. Especially if the foil’s adhesive isn’t the conducting type of adhesive.

If you put a nonconducting layer of material between two conductors you’ve basically built a capacitor. That additional capacitance in the circuit can affect your tone.

If the OP’s bass has shielding paint under the finishing paint like the picture seems to indicate, that finishing paint is an insulator. So I wouldn’t want to apply shielding paint or copper foil over anything until I was 100% sure there is no shielding paint underneath it. Because good luck removing it later on if you have to.

 

[dwizum]

I'm not sure if it's meaningful to try to debate tape versus paint. It's pretty clear that both can work very effectively. It's also pretty clear that you can screw either one up if you have no idea what you're doing and/or are sloppy about it. Some people have a preference one way or the other, so be it.