guitar amp hum nothing plugged in

HELP! Guitar Amp Hum With Nothing Plugged In

There is one issue that seems to be pressing and that is the hum which emanates out of some guitar amplifiers.

Many guitarists spend years modifying their amplifiers to be as quiet as possible, trying different guitar amps or tube amplifiers, or even purchasing a noise reducing/eliminating device in order to get rid of the hum from their existing amplifier.

Related – Guitar amp picking up radio.

What is the Hum?

It is the hum or feedback from the guitar that is emitted from the guitar amplifier when nothing is connected to it. The question then arises, “If I connect no pedals, no cables, nothing but the guitar and turn it on, why does the high-pitched hum come out of my amp?  What about my guitar pickups – humbuckers or single coils?

What Causes it?

To understand what causes this high pitched humming sound that emanates from some amplifiers we must first understand what causes any noise. The noise just like any other sound in nature is caused by two objects interacting with one another. One object vibrating at frequency F1 will produce a sound with a wavelength equal to 2F1. In our case the emitter is actually the guitar and the waveform is the oscillation of body vibrations as described earlier in this article. The waveform is then emitted through air and creates an interference pattern leading to a high-pitched tone that you can hear.

The shape of certain frequencies causes them to create different types of interference patterns, which produce different types of sounds. The shape of these frequencies results from the vibration frequency of the guitar being equal to 2F1. Vibrating higher or lower will have different shapes giving different tones.

So why does this high pitched hum come out?

Now that we know what causes the noise we need to look at why it is so intense in certain amps and not others? This can be due to several factors, such as how the amp is set up, or maybe they just happen to be bad products.

The most likely cause, however, is the sensitivity of amplifiers to electricity. Capacitors are used in the making of amplifiers and they are a poor conductor of electricity. Well, one type of capacitor (which is used in guitar amps) has many plates that have air between them so they cannot conduct electricity well. These capacitors then create an electric field around themselves which spreads throughout the amplifier creating an electrostatic field. So when electricity runs through the amplifier it is influenced more so by the field than by the other components and as a result there is an increase in electrical current. So when no sound is produced the high-pitched hum can still emanate from the amplifier because of this electric field.

It definitely seems so, but as nothing can be 100 percent guaranteed in life we will never know for sure that this is what causes the problem with your electric guitar tone. Just know that if you have a guitar amp and experience this exact problem, it’s probably this issue.

How to Easily Eliminate the Hum?

A simple, yet effective way to eliminate hum is to use a noise gate pedal – my favorite is the BOSS NS-2 which you can see here on Amazon. This pedal will control the signal and stop it from reaching the amp at all while still having all of the other guitar controls accessible. For best results, you want to get a noise gate that has a long decay setting so that you are not cutting off any notes, but rather completely eliminating the noise. This can be a trickier option for some guitarists as it gives up some control over other aspects of the amp (such as tone and volume) which could make them feel less comfortable. The bottom line with this pedal though is that once you’ve got it set up properly, it will eliminate the hum entirely.

In Conclusion

The most likely cause of the guitar amp hum is due to capacitors in the amps. These capacitors create an electrostatic field which affects the electrical current running through it and creates a noise when no sound is produced from either your electric or acoustic guitar.

Once you’ve got a noise gate pedal set up properly, it should eliminate this hum from your guitar amp completely.