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Jazz Shielding Pictorial (Big Images Warning)

#961
Great info.Thanks. I wanted to ask if you know about the cavity in my MIJ Marcus Miller bass? I opened it up and it has a black smooth finish inside. Like plastic almost. Is that shielding ? Should I put copper over that? Thanks
 
#962
I had a look at conductive paints and the test results show that the MG Chemicals carbon based acrylic paint is the best by far. Has anybody tried the carbon paint? I know it is effective on lower frequencies and limits noise from small processors and controller chips but has anybody here tried it?
 
#964
CodyMonster said:
The carbon has a much higher resistance, in the order of 100-1000x vs the nickel and copper/silver versions. It's more for static electricity.

https://www.mgchemicals.com/downloads/category-data-sheets/CDS-Conductive Spray Paints.pdf
Click to expand...

Did you read the frequency response chart that you linked to? I don't think we care about electrical impedance through the applied material for hum and RFI just how much suppression we can get from the material. Look at how much more effectively the carbon paint suppresses the RF energy from 30Hz. to 15KHz. than any other paint.
 
#965
Using copper and other metal foils works, we used copper on secure microcomputers back in the olden days (early 1980s) designing and building Tempest class secure systems for the military. But even heavy copper shielding is not nearly as effective as the spray applied carbon pigment paints.

I can't say people have been doing this all wrong for bass noise suppression because I know using metal foils does work but is not nearly as effective as using a good carbon loaded paint on all bass body cavity surfaces you would use the metal foil.

I will have to use a carbon pigment paint down the road whenever I decide on what new pickups to use in my PJ bass which has the usual Fender single coil J-bass hum and noise.

Annotation 2020-10-29 121625.jpg
 
#968
Lyle Caldwell said:
There have been a lot of questions about shielding and star grounding, so maybe this will help someone.

Here's the schematic I came up with to do this with:

View attachment 2309237


First, I took everything out of the cavities and cleaned them to get rid of dust and manufacturing residue. Then I applied copper foil with adhesive backing to the control and pickup cavities. I tack soldered the seams and made sure each piece of foil read 0 ohms potential with every other piece. Then I made copper tubes (wrapped the foil around a screwdriver shaft of the right diameter) that run from cavity to cavity, tack soldered on each end. I also screwed a ground lug to the wall of the control cavity through the copper shielding. See photo:

View attachment 2309238

Here's the shielding inside the pickup cavities:

View attachment 2309239

Here's a closeup of the ground lug:

View attachment 2309240

Here's the actual wiring on the pots (reference the schematic above):

View attachment 2309241

And here is the other side of the wiring:

View attachment 2309242

Here's the top side of the control plate:

View attachment 2309243

Now, while there is still single coil hum (reduced, but still there), there is no noise at all when the blend knob is centered, and the bass is quiet even when I'm not touching any grounded metal components (strings, bridge, controls, etc). Soon I will put Sadowsky hum cancelling pickups in and the bass will be dead quiet. I also will be installing a S-1 switch in place of the current volume pot to allow series/parallel switching. I'll post that stuff when I'm done.

But for now, I'm pleased. The bass is much quieter, and the control layout (blend, master volume, master tone) is much easier to work with than the stock 62 RI stacked volumes and tones.

The pickups have much more clarity now without being bright (which I can't explain, really, unless it's the cumulative effects of a lot of little changes, like how the pickups are loaded together in the stock configuration and how the absence of RFI and other environmental noise leads to clarity- who knows?).

The tone control is now also much more musically useful (I changed from the stock cheap ceramic caps to a Sprague 715P .047uf cap- the same value that was on the stock neck tone pot, but this cap, or maybe this schematic, allows for more of the tone to be rolled off if needed, and the "sweep" of the tone pot has a lot more "sweet spots").

Please note that I didn't do the actual soldering with the bass exposed like that. I had towels and scraps of old T shirt to protect the bass surfaces when the soldering gun was out.
Click to expand...


Just recently did this with a glarry with a $44 Tone Monster SB-3 & $20 G.M. Phat pole pickup exact same clarity with a centered tone knob! Now how do we get to use our other two tones? Do we need to ground something else?

Want to get it as silent as possible before I do my cheapest build vid

First build noob.
 
#969
I built a J with Aguilar 4J60 pups and want to try this. Is it really worth the time and effort?

From what I'm reading, it appears so. I've never been hugely bothered by the hum though. Just deal with it but am interested in a "dead quiet" bass (PJ and J) Just not sure I'm up for this project as presented. Any short cuts? I bought a roll of Elk 1" copper foil tape of Amazon.

Thanks, Bob
 
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#972
bassdog said:
If I just line each pup cavity with tape, will it make any difference at all?
Click to expand...
It likely would help some, yes (in my opinion). Ideally (and for optimum results) you would want to ensure continuity among all the various sections of applied copper tape and that the overall system is in turn grounded properly either to a lug in the cavity or to the bridge.
 
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#976
I bought something similar that you brush on, but it's very delicate after drying, like it's just a layer of carbon with no real adhesive. Definitely not a solid layer like paint. Maybe I have the bad stuff :D Def easier to apply than copper, and not need to solder all the pieces together to make contact.
 
#977
bassdog said:
Does shielding under the pg make any difference in terms of hum or other single coil stuff?
Click to expand...
Shielding will not help with single-coil hum.
CodyMonster said:
I bought something similar that you brush on, but it's very delicate after drying, like it's just a layer of carbon with no real adhesive. Definitely not a solid layer like paint. Maybe I have the bad stuff :D Def easier to apply than copper, and not need to solder all the pieces together to make contact.
Click to expand...
You don't want to install shielding because the application process will be easy, you want to install shielding because the end result will be effective. And preferably permanent.
 
#979
bassdog said:
But a good idea anyway for other electrical reasons, right?
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Oh yes! I am a firm believe in shielding. A well-shielded bass with hum cancelling pickups should be dead quiet in the vast majority of situations.

And my bias is for copper tape, just FYI. I'm willing to spend the time and do some soldering. And my bass is wonderfully quiet when I'm not playing it.
 
#980
BlueTalon said:
Oh yes! I am a firm believe in shielding. A well-shielded bass with hum cancelling pickups should be dead quiet in the vast majority of situations.

And my bias is for copper tape, just FYI. I'm willing to spend the time and do some soldering. And my bass is wonderfully quiet when I'm not playing it.
Click to expand...

Thanks but I don't want to take the time to do full shielding job right now on my J. My pg does not have any shielding on the underside. Should I even bother with that?
 

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