Guitar Amp Hum With Nothing Plugged In? Try This

The thing with guitar amps is they’re designed to make noise, but that humming noise is the one sound you don’t want it to make. If the guitar amp hums with nothing plugged in, it can be confusing. If this is your problem, read on as we identify why the guitar amp is humming , what’s causing the hum, and how to fix it.

Important Safety Advice

Unless you are an electrical engineer, we wouldn’t advise you to start fiddling about with any electrical equipment as this could lead to injury or even death. A 100 watt amp will be running at least 70volts of direct current which is more than enough to throw you across the room and even stop your heart from beating.

If the fixes suggested below don’t work, you should take your amp to a professional repair centre or learn to live with the hum. Far better to lose a few quid or suffer from an annoying hum than to lose your life.

Why Do Guitar Amps Hum?

There are a few things that can cause an amp to hum, it’s common for amps to make some noise when you’re not using them. All amplifiers make some level of noise, it’s one part of the amps design that can’t be avoided. The amount of noise is determined by the sort of amp and its wattage.

So a 15-watt amp will produce less noise than a 100-watt amp, and an acoustic amp will produce less noise than a high gain amp. A full Mesa Boogie stack is always going to produce more noise than a small practise amp.

So that’s “natural amp hum” but what makes an amp produce a noise that’s not natural hum? It could be a number of things from; mobile phone signals, fluorescent lighting, dust or dirty power (uneven electrical currents caused by old wiring, AC circuits wired up incorrectly, like you’d find in older buildings or venues). 

How To Identify What’s Causing The Guitar Amp To Hum With Nothing Plugged In

The way to work out what’s causing the mystery hum is by a process of elimination. You’ll need to go through each of the following until the guitar amp stops producing that hum. Starting with;

The Settings On The Amp

First up, switch to the amps clean channel, and slowly crank the volume up from 0 to full volume and back down to 0 again. On the clean channel, even with the volume cranked up, the amp should be almost silent. If it’s noisy you can start to cut out the potential causes. 

Check the EQ settings are not fully cranked to maximum, because if the gain is cranked it produces a hiss, treble and presence controls also produce some noise and should never be fully cranked.

Outside Interference

Anything from mobile phones to fluorescent lighting can interfere with the amps signal, creating the hum. Start by moving the amp away from any electronics that are close by, turning your phone off, and turning off the lights. 

Pick-up Signals

Sometimes this hum could be caused by the type of pick-up your guitar has. Single-coil pick-ups generate more noise than humbuckers. That’s why they’re called humbuckers, because they buck the hum.

Ground Loop Problems

If the guitar amp is still humming, plug it into its own socket or multiplug, to check the hum is not being caused by a ground loop. In plain English, ground loop is caused by having too many electrical devices plugged into one circuit. This means that there are a number of ways for the current to go to ground, creating a closed loop – creating the hum.

If your guitar amp is still producing the hum, it’s time to check the amp itself.

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How To Stop The Hum Caused By The Actual Amp

The first thing to check is the inputs, because dust can cause noise. Just spray some contact remover into the input, plug in a lead, and wriggle it about a bit, this should remove any dust from the input. 

Faulty Connections

Now you need to check out the amps’ electrics, because it could be a faulty connection that’s causing the guitar amp to hum.

On the amp, check the;

• Input
• Volume
• Gain
• EQ Controls
• FX or Other Pedal Inputs

It could just be that a connection has gone bad and needs resoldering.

Tube Amps

So far we’ve been mainly talking about solid state amps, but if you’re getting this hum through a tube amp, it could be down to the tubes. The average lifespan of a tube is between one to three years, and a dying tube or a tube that’s already dead, can cause signal chain issues which can cause that humming noise.

SEE ALSO: Here’s How Many Watts A Guitar Amp Uses (the real answer)

How To Cut Down Or Remove Guitar Amp Hum When Nothing’s Plugged In

Now we’ve eliminated the most obvious causes of amp hum, there are a few ways of easing the problem even if we can’t completely eradicate it. Let’s have a look at a few easy fixes that might just get you back on the road without that nasty hum.

Noise Gate Pedal

As we’ve already established all amps have a “noise floor” that’s the level of noise that is produced by the amp when it’s not got anything running through it. A noise gate does exactly what it says, it opens the gate when the noise level is above a certain limit and closes the gate when that noise drops below that limit. Most of the time your guitar playing will be a lot louder than the amp hum so you can set the level to be the same as the hum. You’ll just need to fiddle with the levels a bit to get it to the right level.

Noise gates are popular with heavy metal and prog rock guitarists because their work mixes loud distorted bursts with long spaces in between. Which is the perfect situation for hums to get noticed. Many guitarists find the hum to be part of an authentic “rock/metal sound” but some of us like to sound as clean as possible.

Noise Gate Pedal Control Settings

Noise gate pedals generally have three main settings which are;

• Threshold
  The threshold controls when the gate opens and closes, and is dependent on the signal coming through the pedal. Low threshold will cut all noise apart from your playing, high threshold will only remove the more grating parts of the signal.
• Decay/Release
  This controls the speed for shutting the gate after it opens. If the decay is set low the gate will shut as soon as the signal reaches the set threshold, making your sound a robotic or choppy sound. A high decay will make a softer, more natural sound as the gate closes slowly.  
• Reduction
  Set at high there will be practically no hum, set low and you’ll get some hum, making your sound more rough and authentic.

Guitar Leads

You will probably already have tried replacing your guitar lead, but if the replacement is the same or of the same quality that could be the problem. Try a good quality cable to keep your signal clean, we can’t stress enough the importance of top quality guitar and speaker leads when it comes to background noise elimination.

Ground Lift Switch

A ground lift switch prevents a ground loop, some amps have ground lift switches built-in, check yours, if it does move on. If not you might want to consider investing in one, a decent ground lift switch can be picked up for anywhere from £8.00 to £80.00. It won’t break the bank, but it might just break the hum without electrocuting yourself in the process.

Power Conditioners

If the amp hum noise is caused through dirty power, a power conditioner is an easy fix solution. As part of their make up, power conditioners also have noise filtering which is handy if you might not be in full control of exactly what’s connected to the power loop.

General Maintenance

Sounds like teaching your granny to suck eggs but, making sure all of your equipment is in the very best condition can prevent problems from even starting. Regular checks of all the connections, the amp tubes etc will help to prevent humming and other problems from stopping you performing.

Especially important if you’re on the road for a lot of the time, any little bump or knock could cause something, however small, to get disconnected or partially disconnected. 

Guitar Amp Hums can be annoying, and even more so with nothing plugged in, but don’t lose your cool. Think about it and follow the possible causes step by step and if necessary repair or replace or add either a noise gate pedal, a power conditioner or a ground lift switch.

SEE ALSO: Can You Play Two Guitars Through One Amp?

Frequently Asked Questions