Jazz Shielding Pictorial (Big Images Warning)

[earlysecond]

Yes, it is all anecdotal. All I can tell you is that I shielded on of the inexpensive kits I built because it was noisy. That particular build lives at church. It was noisy there but worse at him because I practice in front of my computer near a computer tower, large monitor and under CFC bulbs. The guitar was noisy. I tore it back down to fix intonation issues, lined pick up and control cavities with aluminum flashing tape because it is what I had here and it became as silent as my other factory bass with active pups. That is anecdotal, BUT also based on my experience and results. I paint guitars, its what I do best. I'm wondering if I could add powdered metal to my first coat of paint, or a special coat, spray the cavities and create proper shielding.

 

[Duder]

For prepping the cavities, do you guys just sand them until they're smooth?

 

[selowitch]

For prepping the cavities, do you guys just sand them until they're smooth?

I actually think the goal is to roughen the surfaces so it has some "teeth" for the adhesive to grab on to. I wouldn't take the time or effort to make it smooth. If, on the other hand, you were using conductive paint instead of copper foil tape, then yes, I might go for smooth.

 

[Duder]

I actually think the goal is to roughen the surfaces so it has some "teeth" for the adhesive to grab on to. I wouldn't take the time or effort to make it smooth. If, on the other hand, you were using conductive paint instead of copper foil tape, then yes, I might go for smooth.

Good to know, thanks!

 

[Killed_by_Death]

I'm wondering if I could add powdered metal to my first coat of paint, or a special coat, spray the cavities and create proper shielding.

The only way that would work is if all that is connected to the chassis ground, which is why shielding paint is the last step of painting a body.

 

[BlueTalon]

For prepping the cavities, do you guys just sand them until they're smooth?

Rough or smooth doesn't matter nearly as much as clean. But all other things being equal, smooth is better than rough.

Smooth or rough, the trick is to make sure all of the tape's adhesive is engaged. I use the back of my fingernail to press down on every single bit of the tape, making a few passes all around, just to make sure it all has maximum contact and adherence. When my fingernail won't work, I'll use anything that won't tear the tape -- silverware handle, popsicle stick, whatever. That should keep the tape firmly adhered to the wood, and previously laid layers of tape, indefinitely.

Then, some of the more anal among us will solder many of the seems, just 'cause.

 

[selowitch]

When applying the tape, an even easier tool that the back of a fingernail is a burnishing tool such as this.

 

[Duder]

I shielded my Jaguar this weekend and, somehow, it actually worked! It looks like a train wreck in there, but when I got to practice it was totally silent. I used copper tape with conductive adhesive and did not solder anything (yet).

Edit: my tool of choice for smoothing out the tape was the butt of a plastic butter knife.

 

[DiabolusInMusic]

Yes, it is all anecdotal. All I can tell you is that I shielded on of the inexpensive kits I built because it was noisy. That particular build lives at church. It was noisy there but worse at him because I practice in front of my computer near a computer tower, large monitor and under CFC bulbs. The guitar was noisy. I tore it back down to fix intonation issues, lined pick up and control cavities with aluminum flashing tape because it is what I had here and it became as silent as my other factory bass with active pups. That is anecdotal, BUT also based on my experience and results. I paint guitars, its what I do best. I'm wondering if I could add powdered metal to my first coat of paint, or a special coat, spray the cavities and create proper shielding.

This is what you want, one can does about 10 basses. A can runs me about $50 CDN from my local supply shop.

Invalid Link Removed

Some other members have tried making their own conductive paint but it didn't go well. This stuff is also a major upgrade from the paint Stew-Mac sells.

 

[selowitch]

This is what you want, one can does about 10 basses. A can runs me about $50 CDN from my local supply shop.

Invalid Link Removed

Some other members have tried making their own conductive paint but it didn't go well. This stuff is also a major upgrade from the paint Stew-Mac sells.

Absolutely, yes! The MG stuff works great and is easy to apply.

 

[Duder]

MG Chemicals Super Shield™ Nickel Conductive Coating

Looks like it's about US$37 from Mouser Invalid Link Removed

 

[selowitch]

In my very noisy Traveler TB-4P bass, I used three coats of the Super Shield in the body cavity and after re-installing the electronics it was a whole lot quieter, even without doing anything else.

 

[Dr Dan]

Rookie questions, so apologies in advance: the pot casings in the pictorial don't seem to be grounded. So, one, is this correct? And two, if so, that means pot casings don't need to be grounded? I thought that they did.

 

[FronTowardEnemy]

Rookie questions, so apologies in advance: the pot casings in the pictorial don't seem to be grounded. So, one, is this correct? And two, if so, that means pot casings don't need to be grounded? I thought that they did.

The pot casings are grounded to the metal plate that are in turn grounded to the overlap of the copper foil in the control cavity.

 

[cheechi]

I wanted to say I read the whole thread. I got to page 16 and think I found a good enough answer but hopefully I can get some 'for sure' advice here.

One thing I noticed with this stock Fender MIM wiring is that they didn't put a ground wire on the jack ground lug. Is it grounded by the collar?

Anyways, keeping things as simple as possible going forward, could I ground each pot to the next, then tone to jack, then jack to the ground lug in the cavity? that way only three wires coming from the jack plate same as in the OP example. Thanks.

 

[Duder]

I wanted to say I read the whole thread. I got to page 16 and think I found a good enough answer but hopefully I can get some 'for sure' advice here.

One thing I noticed with this stock Fender MIM wiring is that they didn't put a ground wire on the jack ground lug. Is it grounded by the collar?

Anyways, keeping things as simple as possible going forward, could I ground each pot to the next, then tone to jack, then jack to the ground lug in the cavity? that way only three wires coming from the jack plate same as in the OP example. Thanks.

I just repaired my friend's Geddy Lee jazz bass and it was set up the same way. I have no idea what's grounding it, but the thing was silent.

 

[BlueTalon]

One thing I noticed with this stock Fender MIM wiring is that they didn't put a ground wire on the jack ground lug. Is it grounded by the collar?

Anyways, keeping things as simple as possible going forward, could I ground each pot to the next, then tone to jack, then jack to the ground lug in the cavity? that way only three wires coming from the jack plate same as in the OP example. Thanks.

There is no wire connecting the ground at the jack's ground lug because the metal control plate is being used as the ground path. The ground lug on the jack connects to the main body of the jack, so connecting a ground at the lug is not necessary, as long as the electrical connection remains good between the jack and the control plate, and also the pots and the control plate.

That said, sometimes those connections deteriorate -- nets get loose, dirt or rust build up in the connection, etc. So to be absolutely sure of a good connection, it's best to use a soldered connection rather than mechanical. Doing what you suggested makes things not only "simple" but reliable as well.

 

[cheechi]

Perfect. Thanks both of you.

 

[amacjazz]

Guys, with all due respect, there's a lot of misleading info here about shielding, fields and "Faraday Cages" etc. You can't lump electrostatic fields together with electromagnetic fields -- both potential sources of interference and noise -- and make anything but accidental progress. Anything electrically conducting like copper is good for electric field shielding and to a small extent high frequency EMG like RF, but bass electronics are already fairly immune. RF is thousands of times higher frequency than bass tones. The hum everyone is aggravated by is 60hz and its harmonic at 120 that comes from anything with a coil (speakers, power supplies, transformers, and poorly shielded power lines in buildings. That's why it changes when you move around. Shielding low frequency EMG requires a material that at a minimum is magnetic which aluminum, copper, stainless steel are not. But even that is not enough because it also must absorb magnetic radiation and dissipate its energy. MuMetal is one such material. When trying to shield a recording space from strong EMG fields in the wiring in my building even 1/4" steel did absolutely nothing. The wavelength of a 60hz mains EMG is about 3,000 miles -- it wraps around everything. But MuMetal is an alloy that absorbs electromagnetic energy and cancels its energy. MuMetal foil is available on eBay. I would not waste my time wrapping electronics and pickup enclosures with anything else. Here is some help from Wikipedia: For static or slowly varying magnetic fields (below about 100 kHz) the Faraday shielding described above is ineffective. In these cases shields made of high Invalid Link Removed metal alloys can be used, such as sheets of Permalloy and Mu-Metal,[5] or with nanocrystalline grain structure ferromagnetic metal coatings.[6] These materials don't block the magnetic field, as with electric shielding, but rather draw the field into themselves, providing a path for the magnetic field lines around the shielded volume.

 

[selowitch]

amacjazz, that's all quite interesting. Do you have a recommendation for what to do in practical terms when trying to reduce unwanted noise produced by a Jazz Bass? Do you think one should use MuMetal instead of copper foil? I've heard someone on TB say that shielding is a waste of time if you “just wire using coaxial cable instead”—is that correct?