Pathfinder 01 - Explorer with upgrades (1st build)

[Simon Barden]

All that can be wired with the pots and switch outside of the cavity.

Make a cardboard template up with the holes for the pots and the switch, and wire those first, along with wires long enough to reach the output jack. You should then be able to place the template with the pots attached over the control cavity and run the pickup wires up to the switched pots and wire those in. Remove the cardboard and fit the pots and switch in the cavity.

I forget how large the hole for the output jack is. You may be able to wire the jack itself up with the harness still on the template and push it through the hole, and then attach it to the jack plate when its on the outside of the guitar. Otherwise push the output wires through and solder the jack socket. Make sure the output leads are long enough to give you enough slack to do this, but not so much that you've got lots of extra cable to somehow push back in.

I normally refer to this channel for wiring as I think he does a pretty good job. https://www.youtube.com/c/SixStringSupplies

[Lappa]

All that can be wired with the pots and switch outside of the cavity.

Make a cardboard template up with the holes for the pots and the switch, and wire those first, along with wires long enough to reach the output jack. You should then be able to place the template with the pots attached over the control cavity and run the pickup wires up to the switched pots and wire those in. Remove the cardboard and fit the pots and switch in the cavity.

I forget how large the hole for the output jack is. You may be able to wire the jack itself up with the harness still on the template and push it through the hole, and then attach it to the jack plate when its on the outside of the guitar. Otherwise push the output wires through and solder the jack socket. Make sure the output leads are long enough to give you enough slack to do this, but not so much that you've got lots of extra cable to somehow push back in.

I normally refer to this channel for wiring as I think he does a pretty good job. https://www.youtube.com/c/SixStringSupplies

Ahhhh! Thank you very much! Makes perfect sense, things got much more clear with this now!


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[McCreed]

Minor detail, but thought I'd point it out...



There's an small unshielded area on the cavity wall by the neck tenon, and what looks like a tear in the tape along the top of the tenon.
You want to make sure you have continuity through all the segments of the shielding material within each cavity.
Hopefully the foil you used has conductive adhesive, otherwise you will need to connect all the pieces by a small dab of solder on each seam.

This can even be necessary with conductive adhesive depending on the quality of the shielding tape. So you'll want to methodically check continuity with your multimeter within each cavity, then recheck after they have been interconnected, then again after your hardware is installed to verify continuity between the hardware and shielding.


Edit to add:
Before anyone calls me out on it, I know gaps and holes are pretty much inevitable in guitar applications, but my personal view is minimising the amount holes and gaps doesn't hurt. And for me, it is more about continuity than "leaks" (and it makes me feel good ). After all, a Faraday cage can be constructed out of wire mesh, which is literally full of holes.

There are plenty of opinions expressed online that shielding is a waste of time, effort and money. I am not of that opinion, simply based on experience, not because I have a deep understanding of electronics. I don't.

[Lappa]

McCreed - thank you for the extended explanation!
I was actually thinking about the Faraday cage myself as well, wondering if 100% coverage even makes sense, because there is no shielding towards the strings anyway…
Also, the shielding foil I could buy turned out to be quite thick and hard to work with in those small, curved spaces. (At least the adhesive is conductive - but I will check with the multimeter anyway.)
None of my other guitars have shielding by the way and I don’t have problems with them - but it’s true I don’t play them in huge arenas either.


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[Simon Barden]

It all helps. Even for open-coil pickups it will block interference coming from behind and to the sides the guitar. And as on stage you normally stand with your back to the amps, then it should cut out any hum from those.

The size of the gaps in your 'cage' determines how effective the shielding is and the wavelengths it will keep out. Any wavelengths smaller than the gap will get in, but any waves longer than the gap size will start to be attenuated as the wavelength increases. With the wavelength 10x the gap size, almost all has been attenuated and at 100x the gap size, attenuation is to all intents and purposes infinite. So even with an open-topped box like a pickup cavity, with say a 5cm longest side, you are effectively blocking all interference that has a wavelength greater than 50cm, so effectively blocking up to at least 600MHz.

Microwave ovens have a grounded metal grid on the door with holes big enough to see through, but they are small enough to block the cm wavelength microwaves used from getting out and cooking you!

Of course not all of an uncovered pickup is inside the box, so it's not perfect, but it does help.

If you fit a covered pickup and the gap between the grounded cover and grounded shielding is say 0.5cm at most, then you're protecting it up to around 6GHz.

The pickup is the bit with the most length of wire on it, so it makes sense to try and shield the pickup as much as possible. The shorter lengths of wire used in the control wiring harness are less prone to picking up noise, but the longer they are the more noise they are likely to pick up, so with a strong source on interference nearby, they can pickup enough noise to be audible, so it's worth shielding the control cavity and using screened cables that run outside the cavity where possible.

As an aside, most '50Hz' or '60Hz hum' you hear on a guitar or bass amp is actually 100Hz or 120Hz hum (plus higher harmonics), especially on valve amps.

50/60Hz is a much lower frequency than you normally hear as hum'. Here's an online tone generator, you can use for a simple comparison in tone. https://www.szynalski.com/tone-generator/

50/60Hz is the mains electricity frequency, and it's what you may pick up from the mains transformer as magnetically induced interference, but most hum is higher pitched and comes after the mains is rectified. You then get positive ripples on the DC supply with 100/120Hz frequency and unless you are very close to the amp, it's this that gets radiated and picked up.

[McCreed]

That's good stuff Simon.

I have read about the relationship of wavelengths and shielding gaps. A lot of it doesn't sink in, but your description at least put it in perspective for me. Thanks!

[Lappa]

Simon Barden, thank you!
If even a wire mesh with 0.5cm gaps would effecticely block all waves under 6GHz - waaaay above the audible range - why bother with perfect cavity coverage?
(Other than personal satisfaction of course wich is a totally legit reason by the way.)


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[Simon Barden]

Partly because you can, and partly because those high frequencies are generally used as carrier waves for other information. E.g. 5GHz is a standard Wi-Fi frequency. All it takes is a bit of capacitance and inductance and the carrier wave info can be demodulated and you're left with the information wave it was carrying. If that is in the audio frequency range, then it could possibly be heard.

I'm far from an expert on these things, but I know from those that do that it can happen.

[Lappa]

Facepalm moment
I covered the hole on my Explorer body ( with the shielding) that is for the ground wire running to the bridge post.
Can anyone point it out to me, where it should be? I would not like to take off the shielding again
Stupid mistake




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[Lappa]

Found it!
Phew.


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