Overdrive vs distortion vs fuzz

At a glance

What's the difference between overdrive, distortion and fuzz?

All three do the same basic thing. A gain stage pushes the signal harder than the next part of the circuit can pass cleanly, and the tops of the waveform get bent or cut off. That's clipping, and it always adds new frequencies called harmonics, which you hear as grit, crunch or buzz.

The names come from guitar pedals and describe how far it goes. Overdrive bends the peaks gently. Distortion uses more gain and a harder curve, so the peaks are cut flat and much less of the original shape survives. Fuzz uses so much gain that nearly every part of the wave hits the limit, and what comes out is close to a square wave whatever went in.

The lines between them are blurry, because pedal makers name their products however they like. A high-gain overdrive can be more distorted than a mild distortion pedal, and the Electro-Harmonix Big Muff, usually filed under fuzz, has clipping diodes and a mid-scooped tone control that put it close to distortion. Ableton Live's Pedal device uses the same three names for its modes, so you'll meet them in plug-ins too.

For the bigger picture of what distortion does to a sound, including wavefolding and bitcrushing, start with the distortion lesson. This page stays with the three pedal types.

Reading the lab

The lab above has three of the saturation lab's curves. Soft clip stands in for an overdrive pedal and Valve for an overdriven amp stage. Hard clip covers distortion at medium drive, and fuzz once the drive is maxed out and the Character knob is turned up to make the curve lopsided. These are simple curves, so they won't reproduce any one pedal's circuit, but the shape of the clipping is what separates the three, and the curves get that part right.

Watch two screens as you go. The close-up of one peak shows the shape: rounded, flat-topped or square. The harmonic screen runs a 110 Hz sine through the same settings and shows each harmonic it adds, odd ones in pink and even ones in amber. The panel on the right reports the crest factor, which tells you how much of the playing's dynamics are left. Auto gain is on, so all three come out at the same loudness as the clean guitar and you're comparing tone with tone.

What is overdrive?

Overdrive started as what happens when you turn a valve amp up past the point where it plays cleanly. The valves can't swing any further, so the loudest parts of each note get rounded off and the sound breaks up. Pedals copied that with a gentler curve called soft clipping, which bends the wave gradually as the level rises instead of all at once.

Because the bend is gradual, the amount of distortion follows how hard you play: pick lightly and the notes stay close to clean, dig in and they break up. That response is why overdrive is the usual choice for blues and classic rock. In the lab, the soft clipper with 9 dB of drive takes the guitar's crest factor from 14 dB to about 8 dB, so the loud notes come down but plenty of the dynamics survive.

The Ibanez Tube Screamer, first sold in the late 1970s, is the pedal most people think of. Its clipping diodes sit in the feedback loop of an op-amp, so as they start to conduct, the gain of that stage falls back towards one and some of the clean signal stays in the output. The same feedback network gives frequencies below about 720 Hz much less gain than the mids. That mid hump is why a Tube Screamer sounds focused and why the low end stays tight.

An overdriven valve amp adds another twist. A single valve stage is lopsided, bending one side of the wave more than the other, and a lopsided curve adds even harmonics. The valve card in the lab with 14 dB of drive and the character at 50% puts the 2nd harmonic, an octave above the note, at −13 dB, louder than the 3rd at −23 dB. That strong octave is a large part of what people mean when they call an amp warm, and the tube saturation lesson goes further into it.

What is a distortion pedal?

A distortion pedal adds a lot more gain and usually clips harder. Push the gain far enough and the tops of the wave are cut off flat, which is hard clipping. A flat top has sharp corners, and a sharp corner can only be built from a long row of high harmonics, so distortion sounds brighter and more aggressive than overdrive.

The ProCo RAT is a good example of the design. An op-amp adds a lot of gain, then a pair of diodes clips the signal to ground, which gives a much harder edge than the Tube Screamer's diodes in the feedback loop. After that comes the Filter knob, a low-pass filter that takes the fizz off the top. Most distortion pedals have something like it, because hard clipping with no filter after it sounds thin and spiky.

The other thing distortion does is even out the level. With 20 dB of drive, everything but the quietest notes gets cut to the same flat ceiling, so the guitar's crest factor in the lab falls to about 3 dB. The notes sustain for longer and the riff sounds solid, but picking harder no longer makes much difference. It suits heavy riffs for that reason, and it's harder to play expressively through.

What is fuzz?

Fuzz is the oldest of the three as a pedal and the most extreme. The Maestro FZ-1 Fuzz-Tone came out in 1962, and Keith Richards used one on the riff of the Rolling Stones' “(I Can't Get No) Satisfaction” in 1965. The Arbiter Fuzz Face followed in 1966 and became part of Jimi Hendrix's setup. Both use two or three transistors pushed so hard that they clip almost the whole wave, with no op-amp or diodes involved.

When nearly every part of the wave hits the limit, what comes out is close to a square wave, whatever note you played. In the lab, the hard clipper at its full 36 dB of drive spends almost the whole cycle of the test sine on one of its two levels, and its odd harmonics land within half a decibel of an ideal square wave's. Fuzz circuits are often lopsided as well, clipping one side of the wave earlier than the other. Turning the Character knob to 100% leans the lab's curve the same way and adds even harmonics, each at about −41 dB; a real transistor fuzz is usually more lopsided than that.

The dynamics nearly disappear. The guitar's crest factor goes under 2 dB, and as each note fades the fuzz keeps lifting it back to full level until the next one starts. On a real pedal, the note eventually drops too low for the transistors to hold up and breaks into a rough sputter. Some fuzz pedals make a feature of that with a bias control, and a Fuzz Face with a weak battery does it on its own.

The Fuzz Face also has a low input impedance, which means it reacts to the guitar's pickups and volume knob. Roll the guitar's volume back and a Fuzz Face cleans up a long way, so the guitarist sets the amount of fuzz from the guitar instead of the pedal.

Overdrive, distortion and fuzz on a sine wave

A sine wave has no harmonics of its own, so running one through each setting shows exactly what each type adds. The figures here come from the lab's harmonic screen, and you can check every one by setting it up yourself.

Read the rows from left to right and the difference is in the slope. Overdrive's harmonics fall away fast, about 10 dB with each odd harmonic, so most of what it adds sits close to the note and sounds like thickness. Distortion's row hardly slopes at all, which puts a lot of energy far above the note, and that's the buzz. Fuzz is the same row pushed to its limit.

The totals tell you less than you'd think. Distortion and fuzz are only about 5 percentage points apart on the sine, yet they sound very different on a guitar, because the gap between them shows up over time: fuzz keeps the whole note squared off right down to its tail, while distortion lets the quieter end of each note through with less clipping. The even vs odd harmonics lesson covers why the amber bars sound smoother than the pink ones.

Playing dynamics through each one

For a guitarist this is the difference that counts most, and it's easy to measure: run the lab's own processing over the whole guitar loop and measure its level in 50 ms slices. Clean, the louder moments sit about 9.5 dB above the quieter ones. Through the overdrive settings that gap is about 7 dB, through the distortion settings just over 2 dB, and through the fuzz settings 0.3 dB, which is effectively no difference at all.

Overdrive keeps your touch, so you can play softly for a cleaner sound and hard for a crunchy one without touching the pedal. With distortion you trade most of that for sustain and an even wall of sound, and fuzz takes the trade as far as it goes: the longest sustain, with every note at the same level however you played it.

The crest factor in the lab's panel tracks the same thing from a different angle, as the gap between the peak and the average level. It falls from 14 dB clean to about 8 dB with overdrive, 3 dB with distortion and under 2 dB with fuzz.

The EQ around the clipping

Each type of pedal shapes the tone before or after the clipping, and that shaping is half of why they sound different. The Tube Screamer gives the bass far less gain than the mids inside its clipping stage, while the RAT filters the top end after its clipper. The Big Muff scoops the mids out after its clipping stages, which gives it a huge, hollow sustain. A Fuzz Face filters very little, so it sounds woolly with a dark guitar and fizzy with a bright one.

You can use the same tricks on any distortion plug-in. EQ before the clipper changes what gets distorted: a high-pass at 100 to 150 Hz going in stops the low strings turning to mud. EQ after it changes the tone of the result, and a low-pass at 5 to 7 kHz takes off the fizz that a guitar speaker would have removed, since a typical guitar speaker rolls off steeply above about 5 kHz. In the lab, the Tone knob is that low-pass.

Aliasing is the other reason to filter after heavy clipping in software. Hard clipping makes harmonics that reach past half the sample rate, and those fold back down as tones that are out of tune with the music. The lab's fuzz settings put that aliasing at −44 dB against the note, the grey bar on the harmonic screen, and switching on oversampling in a plug-in reduces it. The aliasing and oversampling lesson shows how.

Which one should you use?

When you're not sure, start with overdrive. It's the easiest of the three to sit in a mix, and if it isn't aggressive enough, switching to a harder curve gets you further than turning its drive to the top. Save fuzz for parts that play single notes or power chords: a full chord through a fuzz makes so many new frequencies between the notes that it turns to noise, and the distortion lesson explains why power chords survive it.

How to choose and set a drive pedal or plug-in

1. Set the level going inDrive is gain in front of the curve, so the same setting distorts a hot signal far more than a quiet one. Get the input level where you'll leave it before you set anything else.
2. Start with overdriveRaise the drive until the loudest notes break up and the quiet ones stay close to clean. If you want it heavier, move to a distortion curve.
3. Cut the lows going inA high-pass at 100 to 150 Hz before the clipper keeps low notes from turning to mud, which helps most with distortion and fuzz.
4. Filter the top coming outBring a low-pass or tone control down to between 5 and 7 kHz, until the fizz goes but the edge stays.
5. On bass, blend a copyKeep the clean bass and mix a distorted or fuzzed copy in underneath, so the sub stays solid while the harmonics carry the part on small speakers.
6. Compare at the same loudnessAll three get louder as you add drive. Match the output level to the clean sound before you decide which you prefer.

That last setting is parallel saturation with a fuzz curve, and the lesson on it covers the routing in more detail.

Common mistakes

Using more gain than the part needs

More gain feels bigger when you play alone and smaller in a full mix, because a flattened, buzzing guitar covers the same frequencies as the cymbals and the vocal. Turn the drive down until the part loses its edge, then bring it back up a little.

Judging by loudness

Every one of these gets louder as you add drive, and louder nearly always sounds better for the first few seconds. Turn Auto gain off in the lab to hear how big the jump is, then turn it back on.

Fuzzing the sub-bass

A fuzz squares off a 40 Hz note as readily as a guitar note, which turns a deep sub into a buzzy one and fills up the low mids. Blend a fuzzed copy with its lows filtered out, and leave the clean bass to carry the sub.

Trusting the name on the box

There's no standard for what counts as overdrive or distortion, and pedal and plug-in makers use the words loosely. Judge a pedal by how it reacts when you play softly and when you dig in.

Training your ears

The quiz under the lab plays the current sound through one of its three curves with the screens covered, at the same loudness as the original, and asks which you heard. The hard clipper has the flat-topped buzz of a distortion pedal. The soft clipper is the rounder sound of pedal overdrive, and the valve is the lopsided, amp-style curve with its strong octave. Fuzz has no round of its own, since in this lab it's the hard clipper pushed further. Pick the bass or the guitar before you start, since single notes make the differences easiest to hear, and your best score is saved in your browser.

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