Re: Shielded cavities vs shielded wire
Well, it's shielded cable and offers a significantly lower capacitance alternative to the vintage braid style cable. Some brands of it are better shielded than others. The Belden, for example, has a true, braided shield. The cheaper stuff is more likely to have a spiral shield with less % coverage. Where a shielded cable will help compared to unshielded, they all will work to one degree or another. Personally, I use a shielded cable if the switch is in a separate cavity from the pots, like with a LP style guitar. If the switch is in the same cavity as the pots, I usually use regular wire. With maybe a run of shielded from the toggle to the jack.
All I know is that there is a lot of capacitance in the wiring of a guitar like a LP where the wiring to and from the toggle is comprised of 3 lengths of vintage style braided wire ... and maybe especially when the pickups have vintage style leads as well (I'm not sure what the typical capacitance of 4 conductor pickup lead is compared to vintage braid). The capacitance could be lowered significantly by running something like RG-174 instead of vintage braid style to and from the toggle to the control cavity. But I don't know if or how much of a difference you would hear. I've never torn out vintage style wire and installed a lower cap wire to directly compare. I don't think I've ever tried this but, you could run a multi-conductor shielded cable (like 4 wire pickup lead) from the switch to the control cavity. I don't know what the typical capacitance of that type is compared to other types of cable/wire. I assume it's a good clip lower than the vintage style wire.
I have a Godin LP-ish style guitar. Noisiest dual bucker guitar I ever recall owning. No shielded wire used at all and the cavities were not shielded. A little while back, I first replaced the non-shielded with shielded wire (RG174 type). It made a difference but it was still a buzz saw. 3 coats of carbon shielding paint got it pretty close to dead quiet. I'm guessing that shielding the cavities but keeping the unshielded wiring would have been more effective than just using shielded wire and leaving the cavities unshielded, as I first did. But that may just apply to that guitar in my environment. By the way, tone changes were subtle at most. They may have been notable if I had shielded the cavities and installed the shielded wire at the same time. I didn't, which may be why I didn't notice any real change.
I don't have the background to explain the physics behind this stuff. Just relaying my personal experiences.
We can figure out how much of a difference it makes by calculating the resonance from an inductance and a capacitance. Suppose the inductance is 4.5 henries, the pickup's capacitance is 80pF, and the guitar cable is 500pF for a total of 580pF, the resonant peak comes out to 3.1kHz, now add 100pF to that for 680pF total, the peak resonance drops to 2.86kHz, for a loss of 240Hz, which is not a trivial amount.
Rather than use a lower capacitance cable run, I wonder if it might not be better to somehow submerge the channel with conductive pain. It sounds like kind of a mess, though.
Regarding the physics, it's like a regular capacitor. When you have positive and ground metal, such as wire and shielding, closer together, the capacitance increases. When the surface area of those metals are larger, the capacitance increases. When the dielectric constant of the material in between the metals is higher, the capacitance increases. The Gibson style braided shield wire has a high capacitance for several reasons, the center wire is rather thick, so you have a higher surface area on the wire, and since the braided hookup wire is rather this, the center wire and braided shield are closer together. A good guitar cable reduces capacitance by doing the opposite of these things; use a smaller center wire to reduce the capacitive surface, and use thicker cable so that the shield layer is further away from the center wire. Cavity shielding is better than shielded wire, in general, because it puts a lot of distance between the lead wire and shield metal.
Guitarists tend to the thicker gauge hookup wire because it seems more substantial and vintage looking, but the smaller gauge wire you see in low budget guitars is technically super in terms of capacitance, in that the finer wire presents less surface area with which is can capacitively couple to nearby shielding. That stray capacitance between the hookup wire and the cavity shielding is low enough with either, that it doesn't really matter which is used.
