One problem that people frequently come to me with is noise. Often the conversation starts something like this:
"I think my guitar has an earthing problem; there's this loud buzzing..."
"Does the noise get quieter when you touch the bridge?"
If the answer is "yes" then I know that they don't have an earth problem; what they have is a lack of cavity screening and it's probably been that way since the guitar was built.
We live immersed in a ocean of electromagnetism. Everything around us - TVs, radios, mobile phones, microwave ovens, fluorescent lights - conspires to emit radiant wavefronts of electromagnetic radiation which unprotected wiring of your Gibson/Fender/Jackson Megabuckscaster is only too happy to pickup and relay to your amplifier...
Look inside the average guitar and what you will see is a mass of discrete wires commonly known to engineers of a cynical disposition as "the aerial farm".
Let's look at a Squier Strat, for example. It's likely that the wires from the pickups are separate lengths of single core patch cable. So are the wires connecting the various parts of the control circuitry and the wires to the output jack. All of these are potentially acting as aerials sensitive to the powerful EM radiation all around.
The solution is simple: enclose the wiring in a conductive box - a Faraday cage, in effect - which will short the electrical energy contained in the EM radiation to earth, keeping the circuitry inside free from interference.
Unfortunately most manufacturers, under pressure to minimise costs and maintain high levels of productivity, don't spend much time on screening. Those that do often apply it so inefficiently that sometimes it 's worse than useless and if done incorrectly, can actually make the problem worse, not better.
