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How to: Ground a guitar

Ground Loop 1

We expect to Ground all of our pots by soldering a wire to the back of each one, but we can accidentally create a ground loop if we do. Take a look at Fig 1.

Fig 1




Figure 1 shows a standard way to wire a guitar like the Gibson Les Paul and many other two-humbucker guitars. If you look at the image, you will likely notice the backward C created by the ground wires connecting the four pots.

It’s easy to understand how someone might not see the harm in adding a wire between pot four and pot one, as shown in Fig 2. After all, there is already a direct connection between the two.

Fig 2




If you wire your guitar this way, it would work just fine, but you would notice an increase in static. The reason for the rise in static is that you have inadvertently created a loop as you can see in Fig 2. You might not notice the increase in static immediately and so might not attribute it to the added wire.

Even when wired correctly, the backward C created is very close to a functioning antenna and could be close enough to allow noise to enter the signal.

A STAR IS BORN

The best way to solve this problem is to use a Star Ground like the one in Fig 3.

Fig 3




You create a star Ground by choosing one point to use as the central Grounding point and wiring all of the Ground wires to this point. If this point is in a central location, the resulting ground wires will form the image of a star instead of a circle as you can see in Fig 3.

The star ground will resist EMI and prevent you from accidentally creating a ground loop later if you perform other modifications. Each component has only one Ground that leads directly to the star; it’s easy to remember and easy to check.

Ground Loop 2

The second most common way we accidentally create a ground loop is by using a metal control cavity cover. The Fender Telecaster is one of the better-known guitars to use a metal control cavity cover, but there are plenty of others. A steel or aluminum pickguard is another example.

When you attach your volume and tone controls to a metal cover, that cover becomes the ground wire for those components. You no longer need the wires, and if you add them, you will create a ground loop. The electricity can pass through the wires, then through the cover, the wires, cover, etc.

This type of ground loop is worse than the first because it creates multiple loops between the components and the cover. If you were to use a metal shield on a guitar that used the wiring from Fig 1, you would need to remove the ground wires. The result would look like Fig 4.

Fig4




If you wired your guitar the way it is in Fig 4, it would work correctly, and there would be no ground loop to act as an antenna for noise. Strats can also make use of the Star Grounding technique, and any guitar with more than two knobs should use it.

 

Source: humbuckersoup.com