Guitar Hum & Noise

We often get asked about how to reduce electrical hum & noise picked up by electric guitars & basses. It is a such a common problem, that you can frequently see the subject cropping up on guitar forums & websites talking about solutions. It's also amazing how varied the advice about guitar hum & noise actually gets. The fact is that many of us actually know very little about the subject of guitar & musical equipment noise, which is why everyone needs to keep talking about it right? There are a few different reasons why your guitar setup might be noisy.

The following is intended only as a guideline for understanding the nature of electricity & noise as it applies to electric musical instruments. We do not recommend any specific actions, modifications to your electrical system or equipment, & accept no liability for the outcome of interpretation of any information provided herein.

Where does the electrical noise come from?

Electromagnetic Radiation

Electromagnetic radiation is all around us, but not all of it concerns our guitar & music equipment. Most electrical noise is radiated from lights, computers, televisions & intentional radio transmitters to name a few. AM Radio transmitters have been blamed a lot for interference - There's a notable Jimi Hendrix recording where a local AM radio station clearly swamps his guitar & Marshall Stack. Radio stations are a case in point - If you live near a radio amateur or AM transmitter, you may well have heard transmissions through your speakers, even when the amp is turned off!
It's easy to tell that most appliances are radiating when they are turned on - Just get closer to them with your guitar, for most sources you can hear it through your amp, but did you also know that the currents that electrical wires and cables in your walls are radiating too? Whenever current flows in a wire or other conductor, there will be electromagnetic radiation - Some of it you just can't hear through your amp. The kind of electromagnetic radiation you are hearing is actually caused by currents that are changing at an audible rate. The kind of guitar noise that most of us will complain about is radiated 60 cycle hum (50 cycle in many countries outside of the US). In itself, a pure 60 cycle hum sounds just like a low bass note, but we actually also hear noises that have higher tone. Try varying your amp tone knobs & you might well be able to change the way that that hum sounds. There are other frequencies mixed in that are caused by things like the semiconductor switches inside light dimmers. Most commercially available light dimmers vary the light by chopping up the ac current, switching it off at some point in every ac cycle. This actually causes some higher frequencies to be added to the radiated noise - You might well be hearing this as something like a slow buzzsaw sound.
Even though you may be far away from the light dimmer in your living room, the cable that feeds it might well be running near to your bedroom - Sorry, I meant studio! The current that this dimmer switch draws from the cable is causing radiation all along that wire and unprotected instruments will be affected by it.

A popular method of improving guitar noise that is being picked up through electromagnetic radiation is guitar shielding. Check out our Guitar Shielding page for more information.

Electrostatic or Static Electricity

The term "Electrostatics" is used to cover a very broad set of physical phenomena. "Electrostatic noise" or "Static electricity" have often been used to describe certain types of noise experienced by guitar players. By definition, electrostatic is just that - electrically static, which means an electrical charge that is not moving. If it's not moving, it's not causing noise! When an electrostatic charge becomes discharged, it is often called "Electrically Kinetic" under those conditions it can certainly create a crackle or pop. Electrostatic charges can build up on our bodies which can be discharged to your instrument (or for fun to your cat!). They are also the cause of lightning!
A less common complaint from guitarists is the crackling sound caused by the static charge generated by the hand & plastic pickguard as the guitar is played, which then finds a discharge path to your guitar circuit, causing a crackling sound.
Electrostatic discharges are not the cause of continuous hum from your guitar, but in some cases, can be damaging to your amp or effects pedal if they are not tolerant or designed with internal protection.

Capacitive Coupling

Capacitive Coupling is one significant area of electrocstatics we discussed in the previous section above. Noise (more commonly hum) can be coupled into cables and other circuits by a variety of means, including from power cables to your guitar input cable. Capacitance falls off significantly with distance between electrical conductors and in terms of guitar noise is less significant than the effects of electromagnetic radiation previously discussed. In fact, capacitance more likely plays it's most significant part within your signal cables. Capacitance within cables is more likely to hurt your tone than to produce noise. In general, low cost cables are more likely to have higher capacitance which will filter (reduce or attenuate) higher frequencies from your guitar signal, making it sound less alive.

Guitar Signal Cable Noise

Your guitar signal cable is one of the key problem points you should be aware of when it comes to the quality of your guitar signal and noise. Aside from the problems of capacitance and electromagnetic interference we've already talked about, there is also microphoning. Microphoning is caused by the movement of the internal wires and insulation in your cable, sounding like a crackling or even a plastic bag being scrunched in bad cases. The most significant noise comes from movement of the shield in the cable. The copper signal wire is covered by an insulating material. Around the insulation is the braided copper wire shield. Commonly, the shield is the signal or amp ground. The cable has capacitance between the signal wire and shield. This capacitance can store electrical charges that will change as the braid and signal core move. Bending or treading on the cable can cause the shield or signal cores to move. Low cost cables more easily pickup electromagnetic or capacitvely coupled noise. Long cable lengths can also make the problem worse. Generally we're advised not to go above 15 feet of cable length. Investing in cables with high quality insulation, twisted signal wire pairs and double shields will improve the signal to noise ratio.

Ground Loops

You might have read or heard about the mysterious ground loop. It is also often blamed for the hums and noises your music equipment can deliver & the phenomena certainly exists. Remember that we talked about electrical currents causing radiation along wires? This is one of the ways a ground loop can be caused. The ground wire in your electrical system is there to protect you. It is an electrical path that really does connect to ground or the earth at, or near your premises. For every appliance with a metal chassis or case (like your amp), there will be a ground connection (the third pin) that plugs into the wall receptacle. In the event of something going wrong with your amplifier or other equipment, the ground pin will safely provide a way for the electrical current to go, instead of finding a path through you.
The trouble is that our ground wires are really not all exactly ground. The ground wire can also be affected by the currents flowing in the adjacent wiring in the walls, & in some cases by other stray currents flowing along themselves. Once you connect your amp to one outlet & effects units to another, you may well be shorting the grounds between two different circuits or between two distant points on the same circuit, thereby causing current to flow through, & between your equipment, noise then becomes induced in your sound system.
When it comes down to it, any system has an amount of ground noise. Guitar systems however are some of the most vulnerable due to the simplistic way that the signal ground is applied. Pro-sound or studio music equipment often use what are called balanced inputs or outputs with an XLR or tip-ring-sleeve 1/4" jack. A balanced signal is a two wire (plus ground) method of connecting analog audio between audio components, that is independant of the ground, since it is not used as part of the audio signal path. The balanced line signal is also far less susceptible to radiated noise. In a guitar signal cable, the ground is also the shield, which in itself can introduce radiated noise into the amp.

A CAUTIONARY NOTE here - If electrical grounds are improperly connected or open at the electrical breaker box, or even on the electricity company side, you could find that electrical shocks (small or large) might be caused. This might well occur when playing your guitar & singing into your microphone connected to a seperate PA & outlet. Be sure to have the wiring checked if you experience any such problem. As a minimum,we recommend carrying an electrical outlet tester to check the outlet you plug into. Even these cannot guarantee voltage differences of seperate outlets and circuits however.

Shot Noise

Sometimes we think that this kind of noise is confused with the electrostatic kind we talked about above. In fact shot noise is internally generated by components in active pickups, tone circuits or even guitar amplifiers. Any semiconductor (or even a tube) can generate shot noise. Shot noise often shows up as an intermittent mixture of pops, crackles, rumbles through to a mush also known as white noise. In active pickups or on-board tone circuits, the noise may come & go - much to the annoyance of the guitar owner. When this happens, something needs to be replaced. Shot noise is usually a sign of severe damage to semi-conductors - often caused by electrostatic discharges. Electrostatic discharges punch holes in the silicon internal to the components. Successive discharges through the same component cause more & more holes, degrading the component to a point that it becomes unstable and might even be triggered to make noise by such phenomena as cosmic rays!

Pot Noise

Most guitar players will immediately recognize this kind of noise. You turn a guitar volume knob and a crescendo of scratch & crackle is heard through your favorite amp. Sometimes your guitar will get noisy without turning the volume knob. Your amp can also suffer from the same symptoms. The fact is that the pots (potentiometers) contain a conductive track with a contact (wiper) that gently contacts the track. Turning the knob rotates the wiper along the circular track. Nearly all pots you are likely to find inside your guitar or amp are not sealed. Dust can enter the pot housing & interfere with the contact of the wiper to the track. Over time the pot wiper or track can wear out causing the connection between wiper & track to open in places. In more rare cases, the connections at each end of the pot track can be damaged, causing intermittent contact. When this happens, almost any movement of the pot can cause complete volume drop out or even full volume intermittently. Similar problems can occur with tone pots of course, but in this case the tone will mostly be affected.

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