All About Noise

Ever fire up a tube amp expecting that big, glorious guitar tone, only to be greeted by a hiss, hum, buzz, or crackle before you’ve even plugged in your guitar?

Yeah, that can be frustrating.

What you're hearing is the amp's noise floor—basically, the amount of noise an amplifier makes when there’s no guitar signal going into it. Some amps are almost silent at idle. Others seem to have a whole conversation going on in the background.

So, what's the difference?

Sometimes it's the design of the amp. Sometimes it's an old or faulty component. And sometimes it's simply the nature of the beast.

In general, more gain means more noise. But it's not quite that simple. Noise can be introduced by just about anything in the signal path, including tubes, resistors, capacitors, potentiometers, wiring, and the power section. Even the way wires are routed inside the amp can make a difference.

If your amp seems noisier than it should be, the first step is figuring out what kind of noise you're actually hearing.

The preamp is often the main suspect. Your guitar puts out a relatively small signal, so the preamp has to boost it considerably. Unfortunately, it boosts any unwanted noise along with it. By the time that signal reaches the power section, that noise gets amplified even more.

Okay, But What’s Making That Noise?

Before you start replacing parts, listen closely. The type of noise you're hearing can give you some clues about where to look.

Hiss

A steady hiss is often associated with preamp tubes.  An old or faulty tube can be noisy, but some tubes and circuit designs are simply noisier than others. Aging or leaking preamp components can also contribute.

Vintage-style carbon composition resistors deserve a special mention. They're great for getting that vintage vibe, but they're also famous for making a noise that has been compared to—you guessed it—frying bacon.

If the first preamp tube is the problem, swapping a 12AX7 for a lower-gain 12AT7 can sometimes make a surprisingly big difference.

And here's an important point: some hiss is normal. If the hiss is fairly quiet, disappears when you start playing, and doesn't interfere with your tone, there's probably nothing to worry about.

Hum

Hearing a steady low-frequency hum? A 50–60Hz hum can point toward aging electrolytic or power-filter capacitors.

But before blaming the amp, take a look around the room. Modern electronics are everywhere, and phones, computers, lighting, air conditioners, Wi-Fi equipment, and other devices can all create electromagnetic interference that your amp happily picks up.

Crackle

Crackling is a little different. Old tubes, loose tube sockets, oxidized solder joints, and dirty potentiometers can all cause it.

Basically, if there's a connection somewhere in the signal path that isn't making reliable contact, you may hear it as a crackle.

Buzz

A buzz that doesn't sound like a typical 60Hz hum can have several causes. It might be a power-supply problem, interference from another electrical device, or even the way the wires inside the amp are routed.

That last one is called lead dress. If wires are too long, poorly positioned, or carrying different signals too close together, they can sometimes create unwanted noise.

How Can I Quiet Things Down Without Pulling Out the Soldering Iron?

The good news is that you don't necessarily have to open up your amp to start chasing down noise. There are several easy things you can try first.

Try a better instrument cable

It sounds almost too simple, but a cheap or poorly shielded guitar cable can introduce noise right at the beginning of your signal chain. Try a known-good, properly shielded cable and see if things improve.

Back off the gain

Here's an easy experiment: turn down the gain and turn up the master volume.

You'll often get a cleaner sound with less background noise. More gain generally means more noise, so it's really about finding the sweet spot between the amount of gain you want and the amount of noise you're willing to live with.

Try different pickups

If you're using single-coil pickups, some of the noise you're hearing may simply be part of their design.  Humbuckers are designed to reject a lot of that hum, so switching pickups—or even trying a different single-coil—can sometimes make a noticeable difference.

Try replacing the preamp tubes

Remember, the preamp is where your relatively small guitar signal gets its first big boost. If a preamp tube is noisy, everything downstream is going to make that noise louder.

A fresh tube can sometimes be all it takes.

Move the amp

Before you start replacing anything, try moving the amp.   Seriously.

Move it away from your phone, Wi-Fi router, computer, fluorescent lights, air conditioner, or other electronics. Try another outlet or another part of the room. Sometimes simply putting some distance between your amp and a source of interference can make a big difference.

A power conditioner may also help if interference is coming through the AC power.

Still Noisy?

If you've tried the simple stuff and your amp is still making more noise than it should, it's probably time to let a qualified technician have a look.

The fix could be something relatively simple, such as cleaning a connection, resoldering a questionable joint, tightening tube sockets, or replacing a tired component. But until someone actually checks the circuit, it's tough to know exactly what's going on.

And sometimes, the noise is just part of the amp.

Certain designs are naturally noisier than others. A high-gain amp, for example, can be difficult to make significantly quieter without changing some of the characteristics that give the amp its sound in the first place.

That's where a good technician can help separate what's actually a problem from what's simply part of the design.

The Bottom Line

A little hiss, hum, or buzz doesn't automatically mean your tube amp is broken. Some noise is perfectly normal, especially with vintage-style and high-gain designs.

The trick is learning to recognize what you're hearing, figuring out where it might be coming from, and knowing which things you can safely try yourself.

Start with the easy stuff: check your cable, experiment with your gain settings, try another pickup or preamp tube, and move the amp away from potential sources of interference.

If that doesn't do the trick, it's time to call in a technician.

And once you've got that noise under control, you can get back to what you bought the amp for in the first place: cranking it up and enjoying that tube tone.