Questions on shielding / grounding

[Tiga]

I’m shielding a guitar for the first time - an Affinity Strat that I picked up. I’m doing some major mods to it and thought shielding would be a good idea. I put down copper foil with conductive adhesive inside all the cavities, including the input jack cavity, and have the foil slightly coming over the cavity lip all the way around. The new pickguard I purchased came with foil lining the inside of most of the pickguard. From what I can tell when I put the pickguard on the body the copper outside the cavities will touch the foil of the guard.

From doing a little research some people say to put a grounding wire from the input jack cavity to the controls cavity, then to ground that cavity to the electronics ground. It seems to me that since the input jack (which is grounded) is touching the jack ferrule which is touching the jack cavity shielding - And the pots (which are grounded) are touching the pickguard foil which is touching the body cavity shielding - that everything is grounded?

What am I missing? Thanks guys - hope you're having a good labor day.

[Buddha Pickups]

It sounds like everything is grounded.
The input jack ground on a strat can be grounded anywhere if everything is connected anyway. Check for continuity with a multimeter.

Make sure you shrink wrap the hot lug on the jack, so it doesn't ground out.
I normally don't shield the area around the jack on a strat.

[mozz]

"Check for continuity with a multimeter. "
This. If you don't know how to use one, learn. You can spend anywhere from a few dollars to a few hundred.
All copper connected points should show ground, from the strings to the output jack, pot backs, switch screws, etc.
I also don't shield the output jack cavity, but i use shielded wire to that point.

[Tiga]

"Check for continuity with a multimeter. "
This. If you don't know how to use one, learn. You can spend anywhere from a few dollars to a few hundred.
All copper connected points should show ground, from the strings to the output jack, pot backs, switch screws, etc.
I also don't shield the output jack cavity, but i use shielded wire to that point.

This is sound advice. I used the multimeter to check for continuity for the grounding of the wiring harness I just assembled - all good. Then checked the continuity of all the shielding tape I installed - all good. I then checked the "foil" backing of the new pickguard - Nope. I guess it's not foil LOL. So glad I checked before installing the components.

[mozz]

I know most of the strat pickguards I get from China have at least a little foil on the back, never full coverage. I have never tested it, should take my own advice.

[Buddha Pickups]

That foil they put on guards is not always conductive. I normally redo it

[Tiga]

That foil they put on guards is not always conductive. I normally redo it

Does it typically just peel off easily or do you just go over it with foil?

[Buddha Pickups]

That foil they put on guards is not always conductive. I normally redo it

Does it typically just peel off easily or do you just go over it with foil?

I just go over it.

[BatUtilityBelt]

I play the guitar in a few positions relative to the amp before deciding whether/how much to shield. But if moving around is changing the noise floor and I like the guitar otherwise, I'll commit to shielding, sometimes with paint, more normally with foil. The ground has to tie into the shielding, or you're just refocusing where it bounces around. Grounding the shielding sends that noise out. I shield every cavity except the output jack, because you never know what's going to pick up the EMI, and you're building a cage around the sensitive low power electronics. I also twist the wires going to the output jack as I think that keeps whole wavelengths from being transferred to any segment of that wire (theory).

[mozz]

Wavelength of a low E string is about 14ft. The twisting only adds a few pf of capacitance which may be enough to rid the pickup of radio stations. Then there's the balanced unbalanced aspect. Best off to use shielded wire to the output jack.

[andrewsrea]

I personally don't often employ shielding. Occasionally, some Caig shielding paint on a single coil guitar but rarely. Same with shielded lead wires in a guitar, which at their length would be the frequency of inaudible microwaves.

The tradeoff is a lot of parasitic capacitances which will dull the high frequencies, sometimes leaving the tone to be sounding like someone thew a wet blanket over the pickups. Super bright single coils may benefit, but a darker guitar especially with humbuckers are not worth the squeeze, IMHO. It also cuts some of the magnetism which emanates upward from the middle of the pickup, making it quieter and shifting the resonant frequency (again, brightness) of the tone.

If you consider that shielding only blocks electromagnetic interference (EMF) and radio interference (RFI) from the back and sides - the mass of your body against the back of the guitar, pretty much takes care of any noise from that direction. Thus making the shielding noise reduction negligible.

90% of EMF and RFI gets into the pickup through the top side of the pickup, amplified by the 150 yards or so of coil wire wrapped around each bobbin. Which makes them giant antennas.