Saturation

First, let’s get the technical stuff out of the way.

Feel free to skip this!

Saturation is an electrical phenomenon resulting in compression and harmonic distortion. Saturation occurs naturally when electrical component receives a signal greater than it can handle in a linear fashion; there is no longer a direct and simple relationship (linear) between the input and the output of the component. Thusly, the signal or various frequencies are compressed, meaning that for every db going in—above a certain threshold—only some fraction of a decibel is output. There is also harmonic distortion, whereby harmonics—numeric multiples of a fundamental frequency—are generated. Harmonics are directly related to the fundamental frequency, such that for a fundamental frequency of say 300Hz, 600Hz would be its second order harmonic, and so on and so forth.
It is worth noting that our brains can identify a fundamental frequency even it is absent, and only its harmonics are present. This explains why added harmonic distortion might emphasize fundamental frequencies and create presence and energy.

Background

To understand saturation and why we love it, it may be helpful to give a little background on recording technology and methods.

Back in the day, everything was recorded to tape, and many times overdubbed on tape, mixed and summed on tape, and dubbed mixed and summed again! Most or all amplifiers were driven by tubes, as were other equipment. Even many microphones were powered by tubes. Even in the early 21st century, pro studio equipment usually meant a lot of tape and tubes, and otherwise, hardware units used in the recording or mixing process that utilized transformers in their circuitry. After all of that, tracks were mixed on an analog console, also using transformers.

Fast forward to today, and so many amps are solid state, or even digital (like AxeFX, Kemper, Quad Cortex, Helix, you name it). Even if you still play a tube amp, you’re not highly likely to be using tube microphones, or recording and dubbing everything on magnetic tape. You may still have your tracks mixed on an analog or hybrid console and maybe there are some other pieces of processing gear, compressors, limiters, etc. But most people at home, and even pro studios are recording via an audio interface into a computer. These interfaces of today have preamps built into them (no external preamps needed), DI capability for recording instruments direct (no microphones, or amps!), and overall have very low noise, and make imperceptibly little alteration to your signals.

Why you should care

So who cares about tubes and transformers? And shouldn’t I be glad I can record via a USB interface with built-in preamps and skip all of this complicated and expensive analog stuff?

Yes and no.
Having accessible equipment with lots of functionality and low noise is great! The inclusion of preamps and DI functionality means you can worry more about making music and less about more pieces of gear.

On the flip side, it means a lack of coloration. That sounds like it would be a good thing… but have you ever made a recording entirely and only with DI guitars/basses, and microphones right into a consumer-grade interface? Did you think maybe it sounded a bit sterile or lifeless? Sure this could be the result of poor or improperly matched equipment and source material, bad EQ moves in the mix, and other things, but this scenario happens even with the best instruments and performances.

How to use saturation

OK so how do we get around this? Am I just doomed using my USB interface to record? Are you telling me I need fancy tube microphones and an analog mixing desk and tape machines, and—

Whoa! Hold on there, sport.

No, analog gear is not necessary to get the benefits of saturation. In the digital age, just as we have found ways to remove distortion and noise from our signal, we’ve developed ways to add that stuff back in!
There are countless saturation plugins that add compression and harmonic distortion, many of which emulate actual hardware in the way their components saturate and influence sound. Simply find some that suit your fancy and drop them on your channel! Many are completely free, and I happen to prefer some of these free plugins over paid alternatives. Some DAWs include at least one stock, and Logic’s stock vintage EQ and compression emulations act as simple saturators when not applying any reduction (but also when being used normally!) .

You can use saturation all over the mix, on every track, and on the stereo bus. Does a certain track need some additional energy, but you’ve already EQ’d it the way you like? Saturation. You can use it to help bring definition and character to each track, helping them stand out within their sonic area of the mix.

Careful not to overdo it though. A little can go a long way, especially when being used on many tracks and/or over the whole mix. Over-saturation can work against you, sounding a bit too distorted, and smearing definition rather than enhancing clarity.

Bonus application

Try using saturation for emphasis or de-emphasis in a more specific way without simply boosting or cutting EQ. If you don’t have a plugin like FabFilter’s Saturn, or other more controllable saturation tools, try this:

Insert two EQs onto a channel, the first adding or subtracting a frequency band you’d like to emphasize or de-emphasize, respectively. The second EQ should do the exact opposite of the first plugin. If it’s a linear EQ like your DAW’s standard stock EQ, these should 100% cancel each other out. OK so now here’s the trick: insert a saturation plugin in between the two EQs. The saturation will add harmonics to the content after the first EQ, subtlety emphasizing or de-emphasizing the target frequencies, and the second EQ undoes the potentially drastic or just unnatural effect of the first EQ.

Conclusion

Saturation, while such a simple and easily-implemented tool, is a very important part of achieving professional and exciting mixes. It should not be overlooked. In fact, Id encourage you to try using it anywhere and everywhere you can—it’s easy enough to remove a plugin if it doesn’t sound good!

If this seems daunting to you or difficult to understand, that’s OK. Mixing is complicated and has so many nuances and technicalities.Continue on your music production journey, continue to learn and grow, and one day this topic may make A LOT more sense to you.

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