Is shielding required on a passive P-bass?

[N. Kentucky Bass]

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

May we presume an AmPro P-bass cavity is painted with "correctly formulated shielding paint" and "properly applied?" It's probably cheaper for production to just spray the body coat over everything and not bother to cover the cavity.

Also curious about the need for shielding the cavity area for the pickups. If one needs to shield the POTS area, does the entire cavity (including pickup area) need the tape?

 

[DiabolusInMusic]

It won't hurt, and if you're uncertain about whether it's already shielded, conductive copper tape is more effective than conductive paint. Just make sure to get the underside of the pickguard as well to properly enclose the Faraday Cage you're constructing.

Source?

Nickel Conductive Coating - MG Chemicals

Check the specs, it is just as effective as copper tape. The cheap paint Stew-Mac sells might not be as effective but that stuff is junk.

Having worked extensively with both paint and tape (including aluminum), paint is the superior option. It is easier to work with and you can finish a job much faster. It mostly comes down to personal preference though, either option will perform equally as well.

 

[dwizum]

Also curious about the need for shielding the cavity area for the pickups. If one needs to shield the POTS area, does the entire cavity (including pickup area) need the tape?

Possibly, yes.

You have to remember that shielding is basically like insurance. You never "need" it, until you do.

Any conductive part of your bass's circuit can pick up noise. The pots, the wires, the pickup coils, the tiny bits of coil wire inside the pickups that connect the actual coil to the external wiring, and so on. Noise isn't a digital "it's there or it's not there" thing, it's pretty much always there, and just varies in it's intensity. The result of a specific component picking up noise will depend on how strong the noise signal is, how big the part exposed to the noise is, the orientation of the part, where the part is in your circuit, and so on. Shielding a given part helps protect it from picking up noise by reducing the strength of the noise signal by the time it hits a given part.

"Shielding" is just a fancy way of saying "large conductor that's grounded." Shielding basically helps by absorbing some of the energy from the noise signal and shunting it to ground, so you don't hear it. Adding shielding basically becomes a game of wrapping a conductor that's on the ground side of the circuit around all the parts that are on the signal side of the circuit, so the noise is absorbed by the part of the circuit that you don't end up hearing it. Shielding the biggest and most noise-prone components will have the biggest impact, but if you are in a very noisy environment, you may need to shield "everything" in order to really prevent noise.

 

[DiabolusInMusic]

May we presume an AmPro P-bass cavity is painted with "correctly formulated shielding paint" and "properly applied?" It's probably cheaper for production to just spray the body coat over everything and not bother to cover the cavity.

Also curious about the need for shielding the cavity area for the pickups. If one needs to shield the POTS area, does the entire cavity (including pickup area) need the tape?

If it has paint, it is the cheap crap. That is what Fender uses. They are also known for doing half-assed shielding jobs. As somebody that loves Fender, I expect to shield every single instrument, any any price point.

 

[andare]

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.
View attachment 4173590 View attachment 4173591

I did the same to my Player P that had sloppy shielding paint that was doing nothing. Dead quiet now. Why do a half-assed job, Fender?

 

[40Hz]

May we presume an AmPro P-bass cavity is painted with "correctly formulated shielding paint" and "properly applied?" It's probably cheaper for production to just spray the body coat over everything and not bother to cover the cavity.

I’d be surprised if it wasn’t paint shielded. Took me a loooong time to come around to accepting shielding paint. I was pretty much sold on the superiority of copper foil for a long time. But when you consider how virtually every high end bass comes with shielding paint these days, you have to ask yourself if all these custom and boutique shops using it would jeopardize their product’s reputation by allowing inferior shielding? I think not. And considering the cost of quality shielding paint (go through an electronics source and don’t bother with the guitar suppliers) and the time needed to apply it properly, I don’t think it’s all that cheaper for them if it even is. I think it’s been adopted because it just works better for this particular purpose.

Last parts guitar I assembled saw me use paint for the first time. It wasn’t cheap. And I followed the directions for surface prep and applied the recommended three coats and allowed the recommended drying time between coats. And bingo! No noise. So going forward I’m using paint.

Also curious about the need for shielding the cavity area for the pickups. If one needs to shield the POTS area, does the entire cavity (including pickup area) need the tape?

The pickup area is a definite yes. Especially if you’ve got unshielded single coils. That provides at least some shielding for them.

There’s some debate I’ve read about whether it’s worth it, or even necessary, to shield the control cavity.

To my mind it probably doesn’t hurt to do it. But I can’t say whether it’s really needed. About the only downside I can see is if the foil comes loose and shorts something in there. Or some chunk of paint flakes off and does the same.

When it comes to noise the real problem mostly revolves around the design of the pickups. Unshielded single coils are inherently subject to noise. You can minimize but never completely eliminate it. It’s just the way it is from an electronics viewpoint.

 

[micguy]

There are two sources of interference:

1) Electromagnetic hum - wiring and transformers nearby, the currents flowing in them create fields that will make some basses hum.

2) Electrostatic interference - can be any frequency, the voltages on things create electrostacic fields that can cause noises in your bass.

Your bass is pretty well protected against electromagnetic hum, as the pickups (where the vast majority of that problem comes from) are humbucking. Against electrostatic interference, it hasn't got a chance.

A very well shielded Jazz bass (using single coils) is protected against electrostatic interference. Against electromagnetic hum, it doesn't have a chance. The only way to eliminate hum from single coils is to encase them in a magnetic shield, which.....will kill the intended signal.

Any shielding (assuming the shields are grounded) is better than none, but electrostatic shieding relies on conductivity, which is why the copper stuff is better. Wheter it's a singificant or marginal difference depends on a lot of things - mostly how good the paint is and whether or not it's thick enough.

Star grounding is a useful technique - it's especially useful if you're building something like an AC powered amplifier, where there are currents inside that you have to isolate from small signals. In certain circumstances, star grounding is NOT the right way to do things - RF intrusion, you're better off with a short wire to the closest point in the shiielding, as a longer ground wire is an inductor. In a musical instrument, unless you have a preamp in there with a switching power supply, it's not something that you need to worry about. Getting every thing shielded and all the shields grounded is what you need to focus on.

The good news is, your bass, if you do a decent job of shielding it against electrostatic fields, can be immune to most of what's out there. But as is, it's not bulletproof.

 

[themickster]

I wouldn't have thought that passive basses put you at higher risk of covid than active. Shielding is wise, whatever your electrics.

 

[micguy]

There’s some debate I’ve read about whether it’s worth it, or even necessary, to shield the control cavity.

If you're going to have your cell phone on your body while playing, I'd highly reccomend it - it can make the difference between hearing GSM noise from your phone and not hearing it.

 

[ToneMonkey]

Personally, I've not had to shield the entire cavity of a P bass, as I routinely do with stratocasters. The hum cancelling pickup and small amount of shielding on the pickguard seem to do just fine for me.

I have experienced a situation with stratocasters where excessive shielding (full cavity tape job as well as conductive aluminum pickguard) did in fact change the tone slightly. Ultimately in a way I did not like. That might not ever happen with tape in the cavity, but I think it's something to be aware of. It's awfully hard to unshield a body.

Regarding the Player P. I don't believe the body on mine is shielded at all. There's doesn't seem to be another ground wire connecting directly to the body, only the ground wires going to the bridge and jack. Previous MIMs I've owned didn't seem to be shielded either. An early MIM J I owned did not have a hum canceling set. Normally Js hum cancel when volume is equal. These did not, which was obnoxious.

 

[coyote1]

Shielding should be part of every electric instrument build. Period.

It is preposterous that, to get the crispness of single coils, you have to stand a particular way onstage else you generate a swell of hum into the performance.

 

[40Hz]

Personally, I've not had to shield the entire cavity of a P bass, as I routinely do with stratocasters. The hum cancelling pickup and small amount of shielding on the pickguard seem to do just fine for me.

Agree 100%. Any PBass I’ve ever owned (and there have been many over the last 50 or so years) never required shielding beyond whatever shielding they came with. Come to think of it, I’ve never experienced noise issues with a PB. (JBs were a different story! ) But the split-coil humbuckers and minimal shielding on my PBs have always given me noise free operation wherever I’ve played.

There’s a lot to be said for adoption of the philosophy that says: Don’t fix it if it isn't broken. And if in doubt, start with the least elaborate solution and escalate from there only if it becomes necessary. There’s wisdom in sometimes taking the minimalist approach.

A bad shielding job can cause worse noise problems for you than having no shielding.

 

[groooooove]

not required at all. but, it's hard to imagine a situation where shielding wouldn't be a "worth the time or money" upgrade.

copper tape works, or that fancy black paint some folks use.

i've got high end basses with copper shielding, and i recently had a bass modded by a great luthier in brooklyn who used the black paint and that came out awesome as well.

shield away!! good luck.

 

[bassdude51]

Starting with the first split coil P Bass 1957 and going to about 1966, the pickguard was either anodized aluminum or there was a thin full aluminum plate under the plastic guard. There was also a brass shield under the pickup that was grounded to the pots. There was no shielding in the control cavity.

Then around 1967, there was aluminum tape on the back side of the pickguard only in the area of the pots and jack.

I have a 1966 P and it does not hum. Has the full aluminum plate under the guard.

I have assembled multiple P Basses and I've done them with only the aluminum tape on the back side of the guard. That has always worked out fine.

Until..........one time I put together a P Bass with the Fender Original P Bass Pickups and I had bad hum when my fingers touched the magnet poles. I went back over my wiring and found no errors but I couldn't get rid of that annoying hum. (I put clear finger nail polish over the tops of the poles and it still hummed when my fingers touched.)

So, I copied what I saw with Nordstrand pickups. I put a piece of copper tape over the back side of the pickup touching and connecting to the magnet poles and I grounded it to the wiring. Problems solved.

Funny thing is that I've used the Fender Original P pickups before and never had a problem and never had to put copper on the back side over the magnets.

I'd suggest grounding everything! Do the job right! Copper tape or shielding paint. Get a cheap mulitmeter and check for grouding connections at all points. Bridge, shielding, pots, metal knobs, everywhere.

Good luck!

 

[MtManiac]

Title says it all. I just acquired a 2017 Fender American Professional Precision bass. It's the passive model. The POT cavity is not painted black nor does it have shielding. The color of the bass body is antique green, as is the internal walls of the cavity. Should I add shielding? Thank you!

View attachment 4172612

The cavity is actually painted with shielding paint - it's a black layer underneath the green. But no, you should not need it. That's the hum that humbuckers buck.

 

[ToneMonkey]

Until..........one time I put together a P Bass with the Fender Original P Bass Pickups and I had bad hum when my fingers touched the magnet poles. I went back over my wiring and found no errors but I couldn't get rid of that annoying hum. (I put clear finger nail polish over the tops of the poles and it still hummed when my fingers touched.)

So, I copied what I saw with Nordstrand pickups. I put a piece of copper tape over the back side of the pickup touching and connecting to the magnet poles and I grounded it to the wiring. Problems solved.

I've seen brass shields that function exactly as you describe. I believe that they are genuine Fender parts. One piece of brass shaped in the outline of a split P set. I've never used one but clearly there must have been a need at some point.

 

[Gilmourisgod]

What’s the common wisdom on shielding basses with humbuckers? I’m building an Alembic tribute clone with two Soapbar humbuckers, I tend to shield all my basses regardless, but since I’ve never owned or built a bass that wasn’t shielded (except a Ric), I guess I don’t know what I’m “missing” so to speak.

 

[dwizum]

I'd go ahead and shield it. The humbuckers don't protect the wiring in the control cavity or the pickup leads. I've had plenty of humbucker-equipped basses that hummed without shielding in the pickup cavities. Copper tape and/or paint won't impact your tone at all (like a solid metal pickguard or large metal plate can) so there's really nothing to lose by just doing it anyways.

 

[bassdude51]

I've seen brass shields that function exactly as you describe. I believe that they are genuine Fender parts. One piece of brass shaped in the outline of a split P set. I've never used one but clearly there must have been a need at some point.

The problem I had was with a set Fender Original Pickup with the brass shield and it was the one I had to put copper tape onto the back side of the pickup and magnet pole ends.

It was a strange little problem that I never had with other Fender Original Pickups.

 

[andare]

What’s the common wisdom on shielding basses with humbuckers? I’m building an Alembic tribute clone with two Soapbar humbuckers, I tend to shield all my basses regardless, but since I’ve never owned or built a bass that wasn’t shielded (except a Ric), I guess I don’t know what I’m “missing” so to speak.

Shielding gets rid of interference buzz attracted by the electronics. That's a separate source of noise from single coil hum. I would shield every instrument, regardless of pickup type.