Big shielding project idea--mulling it over

[cassius987]

PREFACE:
This is not a "My 4003 is noisy" post. Neither of my 4003s are. But they are, like any bass, sensitive to "environmental issues" like fluorescent lights and dimmer switches, etc. etc. So that's my caveat--I'm not whining about anything.

I ADORE my 4003FL, and with as little bias as I can, I must say that it is the best bass I have ever had the fortune of hearing or playing. I'm so in love with it. That's what inspired me to think of this project... essentially, I thought in my head the other day, "Wow, this thing sounds like a true boutique-level bass and then some. It just doesn't get any better. Pure velvet." And I realized that the only trouble I have ever had with it is really just the kind of trouble anyone playing single coils has... buzzing, humming, radio frequency issues, and so on. I haven't had lots of trouble this way, and none that has affected any of my gigs to the point that the audience knows it, but I feel like this bass deserves to be hum-free. So with that in mind...

I have been looking at StewMac.com at the carbon paint, copper foil, and other shielding products and have read through a few shielding guides (including their own) which get pretty extensive. Would it not be a worthy project to try to do an extensive shielding project on this bass? I was thinking I could shield all 4 cavities (neck pup, bridge pup, tailpiece, & harness), plus the routing between neck pup and harness and the pickguard; if I was feeling really adventurous, perhaps I'd use the copper foil to add extra shielding to the underside of the pickup guard.

My plan of attack is this:
1) Apply 1-2 coats of the carbon paint to all wooden cavities, but don't connect it to ground at this point
2) Apply the electrically continuous adhesive copper foil over the dried coats of carbon paint and ground to the copper foil in the wood cavities, leaving that extra "lip" of copper foil hanging over the edge of the cavities
3) Apply the copper foil to the pick guard
4) Apply the copper foil discretely to the underside of the pickup guard

Keeping in mind that my 4003FL has two Toasters, which are already getting some shielding from their pickup covers, this would be a very noise-free bass, no?

However, I am a novice when it comes to electronics and I want to make sure I know the best ways to ground all of these shields (i.e. to what parts of the electrical system already in place, and where, and how many times). In addition I have heard that you have to be careful in tight areas or else you can cause some annoying issues, such as with the jackplate. I wouldn't really know what to watch out for here.

I'm sure to many of you this smacks with, "If it ain't broke don't fix it", but I love my bass, and I want to do this to further concrete it as MY bass, my MAIN bass, a bass I feel so confident in that I would take it anywhere to play it. You know?

So... with all of that said... any advice?

cassius

[johnhall]

If it's not humming much already, putting all the copper making contact in so many places will certainly make sure it hums like crazy!

Shielding is like zen. More is less and the art is finding the right places to locate it. The basic rules are 1) one small point of contact between planes of ground and 2) no "flying" planes of not-completely-at-ground material to act as an antenna. Other than that, it's trial and error with an excellent possibility that at least one variation will be significantly worse than it already is.

[cassius987]

You make a very strong case Mr. Hall, for the "ain't broke don't fix it" argument... you are correct, I should probably just leave things alone, especially if, as you say, shielding could just bring more hum in than there already was. I really appreciate your advice and the rules you present--I will store them away in my mind. My main hope was just to prevent, say, crosstalk between guitars, etc. etc., as happened to me yesterday morning in a church service when the guitarist powered on his amplifier and pedalboard. It was a quiet buzz, but enough for me to go, "Eh, I should see if I can shield my baby so she doesn't have to be exposed to this foul language," to put it into metaphor.

By the way, your factory put out a SUPERB bass with this 4003FL. I am not trying to kiss any butt here, it's just that incredible.

[nukebass]

I had luck doing the shielding thing on a Mexican P-bass I used to have. It was quiet unless I played at my buddies church that had flourescent lights and then it was terribly noisy. It was dead quiet after the copper tape, but I haven't had the same luck with my DCM. The DCM is noisy and I tried some tape, but I didn't want to take it apart to get to all the cavities (yeah, I figured that wasn't going to work, but I had the tape and a few extra minutes...) since I wasn't sure I'd be able to get it back together again (kind of like Humpty Dumpty). I gave up on trying to fix it and bought an electro harmonix hum debugger pedal and it works great. The pedal is expensive, at $120 dollars, but it is a metal box plugged into a wall that provides excellant hum protection.

[cjj]

You know, I actually did this with my old 4003, using copper foil. I followed all the right principles of EMI/RFI shielding (yeah, I spent several years designing and testing various products that had to pass FCC Class B, so I've got a bit of a clue as to how to do it). All in all, the effect was fairly minimal.

Most of the hum you get from amps & fluorescent lights (transformers & magnetic ballasts) is magnetic fields. The copper trick does little for low frequency magnetic fields (50/60Hz is low frequency). Most of this energy is picked up by the pickup coils, which, if properly shielded from magnetic fields, wouldn't pick up the strings either. To stop magnetic interference takes different materials with high magnetic permeability such as Mu Metal. We used that in microwave spectrum analyzers I used to design. That stuff isn't cheap and you need some thickness to make it work (no foil, more like 0.050 in.).

That's where humbuckers come in. With two coils wound with opposite polarity, you get common mode cancellation, the field affects each coil the same way, but the output from each has opposite polarity so when connected together, the signals cancel.

With single coil pickups, you're always going to be susceptible to magnetic fields.

[rickenbrother]

In my humble opinion, standard single coil pickups will be prone to noise no matter what. Great quality pickups that those from RIC and a good wiring assembly, using high quality cables and a well made amplifier will minimize the hum as much as possible. Humbucking pickups and a good wiring assembly should not be prone to noise. So in either case, I think shielding is not really necessary.

[chrisdski]

Lindy Fralin makes split pickups for a jazz bass. Each pickup if self humbucking. He might be able to do a custom job on a set of Ric pickups, or maybe Sergio would have an opinion on this.

[jps]

...or maybe Sergio would have an opinion on this.

Oh, I'm sure he will!

[chrisdski]

...or maybe Sergio would have an opinion on this.

Oh, I'm sure he will!

Uh- oh

[cassius987]

In my humble opinion, standard single coil pickups will be prone to noise no matter what. Great quality pickups that those from RIC and a good wiring assembly, using high quality cables and a well made amplifier will minimize the hum as much as possible. Humbucking pickups and a good wiring assembly should not be prone to noise. So in either case, I think shielding is not really necessary.

Most likely correct Joey. My 4003 is not noisy, I was just hoping to avoid noise from external sources, but if that's not really possible it's cool. I think the Toasters reduce noise a bit.

[beatlefreak]

The Toasters might be less susceptible to noise simply because they're not as hot, having fewer windings than the Hi-gains.

[cassius987]

The Toasters might be less susceptible to noise simply because they're not as hot, having fewer windings than the Hi-gains.

Yeah, I was thinking that and that they both have those extensive chromed covers.