At a glance
| Property | Saturation | Distortion |
|---|---|---|
| What happens to the wave | Peaks rounded off a little | Peaks flattened, folded or heavily bent |
| Added harmonics, in total | A few percent of the note, up to about 10% | Tens of percent, sometimes more than the note itself |
| Which harmonics | Mostly the 2nd and 3rd, falling away fast | A long row reaching high up the spectrum |
| What you hear | A thicker, warmer version of the same sound | Grit or buzz, often with longer sustain |
| On chords | Mostly holds together | Rough and crowded quickly |
| Where it comes from | Tape, valve preamps, transformers, mixing consoles | Guitar pedals, amp gain stages, clippers, wavefolders |
| Usually used on | Bass, vocals, drum buses, the mix bus | Guitars, lead synths, 808s, effects |
Is saturation the same as distortion?
Yes, as far as the physics goes. To an engineer, anything that changes the shape of a waveform is distortion, and a spec sheet measures it as THD, total harmonic distortion: the level of all the added harmonics put together, as a percentage of the note. An audio interface's spec sheet usually lists THD in thousandths of a percent, because its job is to change nothing.
Saturation is the name for the distortion you get when gear runs out of room gently. The word comes from magnetic tape, which saturates when it can't take any more magnetism, but a valve near the top of its range and a transformer core near its limit behave in a similar way: they bend the wave gradually instead of cutting it off, and they add mostly low harmonics. Pushing a recording a little hot into that kind of gear makes it sound thicker, which is why engineers do it on purpose.
In everyday use, then, the two words describe how far you've gone and what kind of harmonics you've added. A saturation plug-in and a distortion plug-in run the same kind of maths, a transfer curve that says what level comes out for each level that goes in. How those curves work is covered in what is saturation?, and the heavy end has its own lesson in distortion. This page is about where the line between them falls.
Where does saturation turn into distortion?
No meter has a mark where one becomes the other. The same curve can do either, so the answer comes from how much it adds, which harmonics it adds, how suddenly it starts, and what kind of sound you put through it.
How much the curve adds
Drive is gain before the curve. More drive pushes more of each cycle into the part of the curve that bends, so the total distortion climbs. The table shows how far, measured with the lab's own processing on its test sine, a 110 Hz tone at 90% of full scale.
| Curve | 0 dB | 6 dB | 12 dB | 18 dB | 24 dB |
|---|---|---|---|---|---|
| Tape (30% character) | 4% | 9% | 18% | 26% | 33% |
| Valve (60% character) | 9% | 16% | 24% | 28% | 35% |
| Soft clip | 6% | 15% | 28% | 38% | 43% |
| Hard clip | 0% | 21% | 34% | 41% | 45% |
For a sense of scale, tape manufacturers rated a tape's maximum output level as the point where a test tone picked up 3% third-harmonic distortion, so the loudest level tape was meant to take already carried a few percent. By 20% or 30% almost anything sounds distorted.
In between, the percentage stops being much help, because it doesn't say which harmonics make up the total. Two settings with the same THD can sound nothing alike.
Which harmonics it adds
The low harmonics sit on friendly intervals. The 2nd is an octave above the note, the 3rd an octave and a fifth, the 4th two octaves, and most instruments already have them in their own tone, so adding more makes the note fuller without making it sound like a different note. Higher up the series the harmonics get closer together and start landing on intervals that clash: the 7th is a flat minor seventh, and the 11th falls between a fourth and a tritone. They also pile up where hearing is most sensitive. On a 220 Hz note, the 10th to the 20th harmonics cover 2.2 to 4.4 kHz.
That's why a gentle curve can add a fair amount and still sound like saturation. On the lab's sine, tape with 3 dB of drive adds about 6% in total, but its 3rd harmonic is at −25 dB, the 5th at −45 dB, and the 7th is already under −60 dB. A hard clipper with 2 dB of drive adds less in total, about 5%, and spreads it out: the 3rd is at −28 dB, the 5th at −32 dB, the 7th at −39 dB and the 11th still at −48 dB. The clipper sounds harsher with less distortion, because more of it is high up.
Even harmonics, the 2nd, 4th and 6th, come from curves that lean to one side, like a single valve stage. They're a big part of why valve saturation is called warm, and there's more about them in even vs odd harmonics.
How suddenly it starts
A tape or valve curve is never quite straight. Even at 0 dB of drive the lab's tape adds about 4% to its sine, and quieter parts of a sound get proportionally less, so the colour rises and falls with the level and there's no moment where it switches on. Loud notes get a little more and quiet ones a little less, which tends to sound like a thicker version of the same performance.
A hard clipper does nothing at all until a peak reaches its ceiling, then cuts off everything above it. In the table it goes from 0% at 0 dB of drive to 21% at 6 dB, and from nothing to 5% in the first 2 dB. On a real part, that means the loudest notes get distortion and the rest get none, and a sudden change of tone between one note and the next is easy to hear.
What you put through it
A single sustained note is the easiest case. Chords are much less forgiving, because every pair of notes produces new frequencies at their sums and differences. These intermodulation products aren't harmonics of anything in the chord, so they sound out of tune, and they arrive at lower drive settings than you'd expect from soloing one note. The distortion lesson works through the arithmetic for a power chord and a major third.
Drums go the other way. A transient lasts a few milliseconds, so the harmonics from clipping it last that long too, and a few decibels of hard clipping on a drum bus can sound like extra loudness more than distortion. That's why clipping is a standard way to get drums louder.
The rest of the mix counts as well. A saturated vocal that sounds obviously distorted when it's soloed can sound only thicker once the other parts are playing, because they cover its quietest harmonics, an effect called masking. Judge the amount with everything playing.
Saturation plug-ins and distortion plug-ins
The name on a plug-in tells you the range its designers tuned it for, and many cover both. Soundtoys sells Decapitator as a saturation plug-in, and its Punish button adds 20 dB more drive on top of whatever you've set. Ableton Live's Saturator has gentle curves such as Soft Sine next to Sinoid Fold, which folds the wave back on itself. Logic Pro has ChromaGlow for saturation and separate Overdrive and Distortion plug-ins for heavier work. Judge any of them by what they do at the drive you've set, against the bypassed sound at the same loudness.
Guitarists split the same scale more finely. Overdrive sits at the saturation end, distortion pedals clip harder, and fuzz goes furthest; overdrive vs distortion vs fuzz compares them.
Does blending distortion in turn it into saturation?
Partly. A mix control lowers every added harmonic by the same amount, so the total comes down while the shape of the row stays as it was. Put a hard clipper on at 24 dB of drive and blend it in at 15%, and the lab's sine measures about 9% THD, the same as tape at 6 dB. On tape, nothing past the 5th harmonic is louder than −40 dB. On the blended clipper, every odd harmonic up to the 15th is louder than that.
What you get is a quiet layer of distortion under a clean sound. That's often exactly what you want on drums or bass, and it's how parallel saturation works, but the result still has the clipper's edge. To make it sit more like saturation, filter the top off the distorted copy as well. A low-pass at 3 to 5 kHz on the wet signal takes out the highest part of the row, which is where most of the harshness is.
Stacking saturators
Each saturator distorts the harmonics the one before it added, so gentle stages in a row behave like one heavier stage. Take the lab's tape curve at 3 dB of drive: on its sine it adds 6%, and nothing above the 3rd harmonic is louder than −40 dB. Send that through the same curve again, resetting the level to the same peak in between, and it measures 11%, reaching the 5th. Four in a row measure 21%. That reaches the 7th harmonic, about the same total as a single stage at 14 dB of drive.
A session with a tape plug-in on every channel, another on each bus and one more on the master can end up distorted without any single plug-in doing much. If a mix sounds crowded and tiring and nothing looks wrong, bypass the saturators one bus at a time.
When to use saturation and when to use distortion
| Job | Saturation | Distortion |
|---|---|---|
| Bass heard on small speakers | Yes: the added harmonics carry the pitch | Works, but can blur the low end |
| An 808 or bass with grit | Too subtle | Yes, on a copy with the lows filtered out |
| A vocal that sits forward | Yes, a few dB of tape or valve | As an obvious effect |
| Weight on a drum bus | Yes | In parallel, at a low mix |
| Edge on a lead synth or guitar | Adds little | Yes |
| The mix bus | 1 or 2 dB of drive at most | No |
Reach for saturation when the sound is already right and needs to be heard more easily. A bass note at 55 Hz barely comes out of a phone speaker, but its higher harmonics do, and your ear works out the pitch from them. A vocal with a little tape or valve gains harmonics in the upper mids and comes forward without being turned up.
Reach for distortion when the change itself is the point: a guitar that needs sustain, a synth lead that has to cut through, an 808 that should growl on a laptop. Keep it off the sub-bass by distorting a high-passed copy and blending it back in, and expect to cut some upper mids after it.
How to keep saturation from turning into distortion
- Set the level going inDrive is relative to the input, so a part arriving 6 dB hotter gets 6 dB more drive at the same setting. Sort out your gain staging first, so the drive knob means what it says.
- Pick a gradual curveTape and valve curves bend from the start and add mostly low harmonics. Save the clippers for when you want an edge.
- Find the edge, then back offTurn the drive up until the A/B makes it obvious that the sound has changed, then bring it down until it only sounds thicker.
- Watch the top of the spectrumIf an analyser shows energy climbing above about 3 kHz as you add drive, the high harmonics are coming in. Lower the drive or roll off the top after the saturator.
- Check it on chords and in the mixA setting that suits a single bass line can be too much on a pad, and a vocal setting chosen in solo can be too little in the full mix.
- Compare at matched loudnessSet the output so the saturated and bypassed versions are equally loud before you decide anything.
Common mistakes
Trusting the name on the plug-in
A plug-in called a saturator will distort happily if the drive is high or the input is hot. Listen to what it's doing at your settings and ignore the label.
Judging it by loudness
Both saturation and distortion make a sound louder at the same peak level, and the louder version wins quick comparisons. Turn Auto gain off in the lab and the panel tells you by how much. In your DAW, match the output to the bypassed level first.
Expecting a low mix to make it gentle
Pulling the mix down on a hard clipper makes the distortion quieter without making it more like tape. If the blended result still sounds edgy, filter the top off the wet signal or switch to a softer curve.
Setting it on single notes and playing chords
Chords bring intermodulation, so a pad or a guitar chord needs less drive than a bass line or a lead to stay on the saturation side.
Training your ears
The quiz under the lab plays the current sound through tape, a soft clipper or a hard clipper, at the same loudness as the original and with the screens covered, and asks which you heard. Tape is the gentlest and darkest of the three. The hard clipper puts a buzz on every note, and the soft clipper sits between them, so for that one listen for how much fizz there is above the note. The bass and chords make the differences easiest to hear, and your best score is saved in your browser.
Questions people ask
Is overdrive saturation or distortion?
Overdrive is the guitarist's word for the gentle end of distortion: a soft-clipping pedal, or an amp pushed just past clean. It overlaps with heavy saturation, and the difference is mostly which world the word comes from. Guitar pedals that call themselves distortion usually clip harder and add more.
Is clipping saturation or distortion?
Light soft clipping is saturation by any definition. Hard clipping is distortion whenever you can hear it, but on short drum peaks a couple of decibels of it often can't be heard at all, because each burst of harmonics lasts only a few milliseconds.
Can a saturation plug-in make distortion?
Yes. Turn the drive up far enough and any saturation curve flattens the peaks and adds loud harmonics. In the lab, the tape mode sounds like saturation at 4 dB of drive and like distortion at 30 dB, with nothing else changed.
Which is better on bass, saturation or distortion?
Saturation when the bass has to stay smooth and you mainly want it heard on small speakers, since the added harmonics carry the pitch there. Distortion when you want grit, and then on a copy with the lows filtered out, so the sub underneath stays clean.
How much distortion can you hear?
There's no single figure. Low harmonics sit under the note's own overtones, so several percent of 2nd and 3rd can pass as extra thickness, while the same total spread over high harmonics is much easier to pick out. A busy mix hides more than a soloed track does.
Why does my saturation sound like distortion?
Usually the level going in is hotter than you think, so the drive is higher than it looks. A harder curve, chords instead of single notes, or several saturators in a row all push it the same way.