Working on the noise issues of the Flying V. I believe it is related to the pickups. If I ground the signal chain anywhere the noise goes away, so it is coming from the signal source itself, the pickups. The pickups are humbuckers but I assume they are the cheapest turds, given the $200 price of the whole guitar. Can spend over $200 on just pickups.
None of my other guitars have any shielding in the cavities. I think it is a band-aid/work-around type solution. Trying to make a perfect faraday cage for a pickup isn't possible.
Same electrical fundamentals apply to an electric guitar as anything else. There are two basic type of antennas that couple noise. A loop and a pole. The loop is very low impedance, and the monopole is very high, as it is only connected on one end. Both will always receive electromagnetic radiation. For a loop, the induced signal level is proportional to the loop area, and the magnetic flux though it.
For a monopole it is more complicated.
I have some aluminum foil 'duct' tape, however the adhesive electrical conductivity is unknown. So for $7 I bought some copper foil tape with conductive adhesive that I can easily solder to.
Removed the stings, pickups and pots to be able to line the cavities with foil. I was also able to use a M8 bolt and a prybar to remove the lower bridge pin to ground it properly.
The existing ground wiring from the manufacturer is distributed. All parts are connected with wires, but at different places. The pickups are grounded to the pots, which are grounded to the switch, which is grounded to the tone pot, that is connected to the bridge and jack. The pickup wires are coax, and have essentially no loop area. Shielded. Beyond that loops everywhere.
Lined the cavities with the foil tape. It's thin and tears in the corners, so have to stick small pieces over the holes. Also did the back side of the pick guard over the cavity area.
Each cavity of foil must be grounded to do anything, otherwise it is still an antenna. Soldered wires to each of them, except for the pick guard as it is already grounded by the bodies of all the pots and the switch.
I decided to do a 'star' or single ground point style of wiring. Reduce the loops. Everything to one location, that is 'ground'. Ideally this would be the jack ground terminal, as that is the reference for the amplifier at high gain, but not physically possible. So inside the pot cavity. There are nine wires in the one node. Three foil cavities, bridge, three pots, switch and jack.
There are still loops in the system, shielded coax would be better than the normal signal wiring (red). But ground only one end of the shield, the receiver side, otherwise you make another loop. So the switch inputs, tone pot input, and jack.
So, how does it perform? Better but not great. More noise than any of the others. Still need to attenuate the high frequencies with the tone knob to prevent feedback. But can play it at full power, so that is a win.
Why does it squeal at high frequencies? All electrical systems have some capacitance/inductance/resistance and make a resonator. The reactive components increase with frequency. For whatever reason this guitar has a peak in the band of frequencies it can produce, which isn't good. But for now it is at least useable. Maybe try the shielded wiring.
