Ground loops can cause humming and buzzing in your guitar.
Do they ALWAYS cause humming and buzzing in your guitar. No, not 100% of the time. But wouldn’t you rather eliminate the possibility if you are rewiring your guitar?
The traditional way that guitars are wired is to have a common ground for both the signal ground and the mechanical/chassis ground. The outside lug of the volume pot is soldered to the back of the pot. The pots are then either connected with a piece of wire soldered between the pot cases or the pots all touch the metallic shielding. Eventually, all the grounds are connected to the (-) terminal of the output jack. Mixing and/or interconnecting the two types of ground can introduce hum to your signal.
A ground loop occurs when a signal ground has two or more paths to the (-) terminal of the output jack. This is most obvious when the guitar has the pots touching the shielding (a metal plate or metallic foil) and the pots are connected together with a wire soldered to the backs of the pot cases. Since the ground signal travels from pot to pot over both the wire connecting them and also over the shielding connecting them, it causes a ground loop. Ground loops can cause hum.
Manufacturers are famous for doing this. In Stratocasters, for instance, they apply a small amount of foil shielding to the pickguard and then solder a piece of wire between the pots grounding them together as well creating a ground loop. The reason they do this is fairly simple if you think about it. The pickguards are manufactured by a company that supplies them to Fender® and the pickguard manufacturer applies the shielding. The wiring harness is built by Fender® employees on a separate assembly line. The ground wire between the pots holds the wiring harness together before it is installed into the pickguard. No one considers that the connecting wires (or the shielding) creates a ground loop.
The same situation exists in Telecasters. Rather than having the pots touch shielding, they touch the metal control plate. Which is fine. The metal control plate grounds the pots together. The problem comes into play when the pots are connected together with an additional piece of wire soldered between the cases. That creates a ground loop. Not good.
Here’s a very simple and easy way to tell if you have a ground loop issue: put your finger on a ground connection in your guitar’s wiring. Now, trace the route of the ground without lifting your finger off of the connection. If you can end up at the same spot where you started without lifting up your finger, you have a ground loop.
There are a lot of things that have to be done correctly in order for your guitar to create beautiful, sparkling, clear, hum & buzz-free tone. Avoiding a ground loop is one of those things and an easy one to avoid.
Call our shop – (614)600-1001 – if you’d like to talk more about ground loops or any upgrades to your guitar. We live for this stuff.