If you have shielding in the cavities of your electric guitar but are still experiencing too much ambient buzzing, one of the causes can be ground loops.
Guitar shielding ground loops are created when electronic components have two earth connections, one of them being the earthing created by the shielding itself.
Ground loops won’t stop your electric guitar from working properly, but in some cases can cause unwanted noise in your signal chain.
Many electric guitars with shielded pickguards have this potential problem, but how do you find if your guitar has this problem, and then how do you fix it?
Fortunately it’s fairly easy, and I’ll show you how – without getting too techy!
What Effect Do Ground Loops Have on Sound?
Ground loops allow electricity to flow around the extra ground circuit that would normally not be there with a single earth path.
This happens because electrical loops act as antennas, and pick up electromagnetic interference from other electrical sources close by.
So once your guitar is near a fluorescent light bulb or other noisy electrical device, the ground loop antenna in your guitar could add a small amount of electricity into the circuit, and you could hear this as unwanted noise from your amp.
In some places you might not notice any effect on the sound, but if you play your guitar in another place (or even another position in the same room) you can get extra white noise through your signal chain.
Particularly if you are recording, this can be undesirable.
The caveat with shielding ground loops is that they really won’t have any effect unless your guitar has active pickups, and even then it’s not too likely. Why? …well keep reading and you’ll find out.
Why Do Guitar Shielding Ground Loops Happen?
Often this can just be caused by the manufacturing process, where a shielded pickguard is provided by one manufacturer, and the controls are pre-wired by another with an existing common earth wire.
Once the two components are put together by the guitar maker, they end up with the shielding acting as one earth, and the common earth wire as the second.
This is not always the case, and often ground loops occur due to someone modifying the electronics in their electric guitar, or have added shielding.
Some guitar makers like to use star-grounding to avoid loops, which means there is a single earth point with all earth wires going only from that point to one component per earth wire.
How to Spot Ground Loops
The wiring connecting the electronics in your guitar could be messy – and often is!
As long as your guitar works correctly, you can ignore all the wiring except for the earth wires which are soldered to the component bodies.
You can visually inspect your guitar’s electronics to see if the body of the volume controls, tone controls, and switches are touching the shielding underneath the pickguard.
If they are, then take a look to see if there is an earth wire also soldered between the bodies of these components.
Finding both of these in place tells you instantly that you have a ground loop.
Do Ground Loops Actually Matter With Passive Pickups?
Here is where there is some contention.
A ground loop is created when current flows from a power source to ground, and with passive pickups there is no power supplied to the guitar, so in theory there is no power to flow through the extra Earth circuit.
Another thing to remember is that if your guitar is shielded properly, any wire loops inside the cavity should be shielded from outside electrical fields, stopping them from acting as an antenna.
It’s unlikely that multiple ground paths in your active pickup electronics will create extra noise, and mostly people complain that it happens when using two amps or multiple sound effects devices.
- The issue here is normally that they have created a ground loop with the cable connections between the guitar and amps, and this is what causes the noise.
Even then, you will only truly create a ground loop if the amps and FX units are plugged into separate AC power outlets, and each outlet has a slightly different ground potential, allowing a small amount of power to run through the Earth circuit.
Active pickups are different to passive pickups, since they have a power source (a battery) providing power to the electronics. In this situation you could possibly have electricity flow through a ground loop, causing extra signal noise.
How to Fix Guitar Shielding Ground Loops
It’s simple to fix ground loops, you just need to look at each component individually, and ensure there is only one Earth connection, whether that is through the shielding or a wire.
Just note that if you are relying on the shielding as an earth, then that shielding needs to have a solid electrical connection back to the main Earth wire.
Note that some shielding is very thin, and if you rely on this for your earth it could fail at some point in the future.
The tricky thing if you choose to remove extra earthing is to ensure that you maintain a good solid earth connection between all components – and this is important for your safety as well as reliable operation of your guitar.
If you have ground loops in your passive pickup guitar and don’t have excessive noise, then you’re probably better off leaving it the way it is. Good Earth connections are a must.
For ground loops in active pickup guitars, it’s best to remove them.
After removing ground loops, get handy with a multi-meter, and make sure that you get very low resistance between the Earth of all your guitar’s components (including the strings, bridge, and input jack).
No matter how you approach ground loops in your guitar, just note that it is extremely important to have good earth connections in your guitar.
If controls move around a bit with use, eventually they can lose their grounding to the shielding, and can start to cause sound issues – or even stop working entirely.
If something goes wrong with your amp and electricity gets passed to your guitar, you can be electrocuted if it is not grounded correctly.
If you have an electric guitar with passive pickups, then guitar shielding ground loops are unlikely to cause you problems, and for the sake of safety it’s best to have wires that earth your guitar securely.