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Saturation Strategies

Saturation Strategies

Saturation effects can be used in different ways to make mixing easier. Find out how...

Saturation can be one of the most helpful and versatile mixing tools available to you. Depending on how you employ it, it can leave you needing less EQ and compression, and sometimes it can even be used in their place. But it’s also very easy to overdo it! In this article, I’ll consider a few different ways in which you might take advantage of saturation to improve the quality of your mixes.

You can listen to audio examples on this page or download the ZIP file below and audition the 24-bit WAV files in your own DAW.

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What Is Saturation?

Softube’s Saturation Knob is a great freebie saturator. But did you know it could help you get better results from your drum or vocal compressor?Softube’s Saturation Knob is a great freebie saturator. But did you know it could help you get better results from your drum or vocal compressor?The term ‘saturation’ once specifically described the effect of overloading analogue circuitry or recording media — think valves, inductors, transformers, op‑amps, loudspeakers, magnetic tape and vinyl — by passing high enough signal levels through them that they were operating outside of the designer’s intended ‘linear’ range. Non‑linear behaviour can be incredibly complex, producing harmonic distortion, tonal change and dynamic effects that all vary considerably with level. This is why when you hear a mix engineer use the term ‘saturation’, they usually also offer at least one enticing but slightly vague description of the quality it brings to an audio signal: warmth, glue, grit, vibe, cohesion, girth… you get the idea!

Today, we have access to an almost bewildering range of hardware and software gizmos that either emulate this aspect of specific analogue processors and media, or are designed from scratch to deliver an appealing saturation‑like complexity. Some equip the user with a huge degree of control, while others aim to deliver the perfect sound with only a knob or two. There isn’t really a ‘best’ tool to choose, or a ‘correct’ way in which to use it: the sort of character they can add to different sources is very much a matter of personal taste. But when choosing your tools, it’s worth considering just what it is that you want to achieve. With that in mind, let’s consider some helpful saturation strategies.

SoundToys’ Radiator: a characterful saturation plug‑in which mimics the vintage Altec 1567A rackmounted tube mixer.SoundToys’ Radiator: a characterful saturation plug‑in which mimics the vintage Altec 1567A rackmounted tube mixer.

Console Yourself

First, let’s look at how you can recreate in a software DAW the way saturation might come about when mixing on an analogue desk. Depending on an analogue desk’s architecture, a source might pass through several transformers, op‑amps or valves on its journey between the channel input and the speakers, and each can have an effect on the sound. On a vintage Neve or API desk, for example, an audio signal typically passes through several transformers and active gain stages, each of which adds a very subtle character. So too will any outboard processors or effects and, if you’re recording to it, analogue tape. This effect can be exaggerated by running the signals ‘hotter’ into any of the various stages. This is what people are referring to when they describe mixing ‘into’ a desk or making a desk ‘bend’.

Some software DAWs already have analogue emulation built in. For example, Pro Tools has its Dave Hill‑designed HEAT feature, Universal Audio’s LUNA offers Neve and API‑style summing, and Harrison’s MixBus 32C is designed to deliver some of the sound of their most famous console. But it’s fairly easy in any DAW to set up something similar using plug‑ins — and because there are so many suitable plug‑ins, this can give you a little more choice over the nature of the saturation character too.

If you really want to go to town recreating a console‑like feel, Plug‑in Alliance’s channel strips have a tolerance‑modelling feature that simulates the minute component‑level differences between channels on an analogue console.If you really want to go to town recreating a console‑like feel, Plug‑in Alliance’s channel strips have a tolerance‑modelling feature that simulates the minute component‑level differences between channels on an analogue console.I’ll often start a mix by inserting an instance of the same analogue‑modelling channel strip plug‑in on every track. In a typical mix, I’ll have several subgroup buses, through which the audio passes on its way to the master bus, and I’ll have the same channel strips on all of these too. Although I use different plug‑ins on different projects, I prefer to use the same plug‑in on every channel within a session, rather than mixing and matching. It’s less that I’m trying to recreate a specific console’s sound and more, as with any console, that the consistent control set means I’m able to jump quickly around and get a mix in shape.

Depending on the nature of the project I’m working on and how it was recorded, I might also mix into tape‑emulation plug‑ins (or other plug‑ins that add more character as more level goes into them) on my groups: the drum bus, guitar bus and so on. The more you mix this way, the more you begin to hear how the sound changes as your music passes through groups that contain more of these character‑imparting plug‑ins. You begin to get a feel for how far to push things and when to back off a little. I particularly like to use this ‘virtual console’ approach if mixing a typical rock‑band sort of production, with several parts; there’s a satisfying familiarity to the sound if I use an SSL channel‑strip emulation on drums and guitars in particular (a very well‑trodden path!).

You should listen out for bloat in the low mids when working in this way, especially if you’ve added multiple stages of saturation on channels, groups and the mix bus. And anyone who’s not familiar with analogue mixing should also note that to get the most out of working this way, you have to pay close attention to gain staging; while DAWs themselves can handle massive signal levels, it’s all about hitting these analogue‑emulation plug‑ins in their saturation sweet spot as you mix.

Top‑Down: A Simpler Approach

A simpler saturation strategy, which I find can still work very well for an overall mix, focuses on the master bus. It doesn’t stop you deploying whatever processors you wish on the individual channels, but the idea is that the mix bus takes care of the heavy lifting. Again, you’ll still use several ‘layers’ of saturation, asking most of these tools to make only a small contribution to the overall sound. I can’t offer you a scientific reason for why that works better than driving one stage harder (perhaps it’s that many analogue emulation plug‑ins tend to be modelled more accurately in their intended range of operation?) but it certainly works, and not only for me: it was a description of this approach by Tchad Blake, arguably one of the most successful proponents of mixing ‘in the box’, that first inspired me to try it.

Here’s an example of what it might look like. Start with a tape emulation plug‑in, or perhaps even two, at the start of your stereo mix‑bus chain. Then follow this with some kind of dedicated saturation device, such as FabFilter’s Saturn, or a vintage‑style EQ. Tchad Blake himself then leans hard into the Sonnox Inflator plug‑in, which has a tube‑like effect whilst also increasing apparent loudness. The choice of specific tools, though, is less important than how you use them. Essentially, it’s about finding a combination of sounds that you find pleasing across the whole mix. With this multi‑stage chain doing much of the work, you generally need less of this sort of processing on individual tracks, which is welcome news if your computer struggles to keep up with, say, 24 channels of saturation and more on your buses! That said, I’ve noticed that it can also lead you to make significantly different decisions when it comes to things like EQ and compression on the individual channels and group buses.

An example of multi‑stage mix‑bus saturation.An example of multi‑stage mix‑bus saturation.

One tip I’ll offer for when you’re using this technique is to make sure you have a way of changing the signal level going into this stereo‑bus chain. Some DAWs have an input gain control for the master bus; alternatively, you might place a dedicated gain plug‑in at the start of the chain, or you could create a kind of ‘pre‑master’ auxiliary channel, through which all the channels pass before reaching the master bus. This way, if you think the processing is getting too much you can pull things back very easily without having to unpick your mix. It can also be a handy target for a little creative automation on the whole mix.

Another insurance policy is to keep your actual master stereo bus free from processing, and use a pre‑master bus to host the processing chain. This way, if the overall approach is working well, but later in the mix you find that it’s tending to suffocate just a couple of sources, you can either route those sources past this processing altogether, or send a little of the clean signal past the processing, for a more subtle effect.

Generally, this top‑down technique is much easier to manage than the full‑on console recreation. It’s also fairly easy to tweak or bypass an element of the processing if you feel it’s not working, or if you think it might be causing too much of a build‑up in the low‑mids. Personally, I favour this approach for productions with sparser arrangements, but you can still get very heavy‑handed with it if that’s what’s required to bring a track to life!

Parallel Lines

It’s quite common now to see mixers using parallel saturation/distortion on individual sources, group buses and even the master bus. It’s an approach that can have many advantages. For example, Miloco engineer Jamie McEvoy told us: “I often find [saturation] more useful than compression because it shapes tone as well as controlling dynamics. I prefer to do these things parallel in order to not affect the main sounds and to give me more control over the parallel sounds.”

If you’re unfamiliar with the concept of parallel processing, it essentially means that you split the signal into two paths and process one path but not the other, before blending the two to taste. Some plug‑ins have a wet/dry blend control to make this easy but there are advantages to setting up the routing in your DAW, to put the clean and processed sounds on different tracks in your project. This way, you can EQ and process each path differently — for example, by filtering or equalising only the saturated channel, to focus its energy in a particular frequency range that helps to reinforce the clean track where you feel it’s lacking.

Parallel processing can be a great way to use saturation to inject a sense of excitement and fullness into pretty much any element in a mix.Parallel processing can be a great way to use saturation to inject a sense of excitement and fullness into pretty much any element in a mix.

An advantage of parallel saturation is that you get much more extreme with the processing, and this can not only deliver a different character but also create some interesting side‑effects. For example, I often like to use an extension of this technique over a whole drum kit or drum loop. I’d set this up by routing all my drums through a subgroup, so that I can process them as a whole, and then set up an effects return (aux) channel that hosts both my saturation plug‑in of choice and an EQ plug‑in that has a polarity inverter switch on it.

Once you’ve played around for a while, obliterating your drum sound, turn the level of the send track down a touch and try flipping the polarity whilst making some extreme moves with low‑ and high‑pass filters. Don’t be surprised if this technique doesn’t work the first time you try it — often it won’t — but sometimes it can create dramatic tonal change in the drum sound, adding real character. On slower‑tempo tracks in particular, it can feel like it’s extending the bottom end of the kick drum in a very cool way, and this effect can also work well on vocals and bass instruments.

The beauty of using an effect in parallel is that we can dial in just the right amount of character or vibe, whilst ensuring that the original sound doesn’t feel very heavily processed — even if it is! It can also serve a similar role to parallel compression, to bring up the lower‑level details without squeezing the life out of the sound overall.

Multiband Saturation

One of the main pitfalls you might encounter when using saturation in a mix is that it can, by its very nature, reduce the perceived clarity of a source. This ‘blurring of the lines’ is exactly what we look for much of the time, but on very low or high frequencies it can also rob a mix of its power or clarity.

One solution is to use parallel processing, with some low, or high‑pass filters in place on the ‘processed’ track. Another is to create that ‘pre‑master’ bus I mentioned earlier, and route some sources around any group or mix‑bus saturation. But we also have the option of multiband saturation. Indeed, we now have some very clever saturation plug‑ins at our disposal that allow us to split the processing over several frequency bands. FabFilter’s Saturn is a great example and a tool I use often when mixing. Like multiband compressors, it allows you independent control of the effect in different frequency ranges, but unlike compression, processing one band generates harmonics, thus injecting energy higher up the spectrum.

Multiband saturation tools like FabFilter’s Saturn plug‑in allow you to split a signal into different frequency bands, each of which can be saturated differently.Multiband saturation tools like FabFilter’s Saturn plug‑in allow you to split a signal into different frequency bands, each of which can be saturated differently.

Bass guitar is a great candidate for this sort of treatment. We often want the true bass region of our mix to sound clean‑ish and a multiband saturator allows us to leave the sub‑100Hz frequencies clean, thus retaining the weight and power of the bass instrument, while really getting stuck into the 1‑2 kHz region to make it ‘speak’ so much better on small playback systems. It might be the other way around on drum overheads or a drum bus: we might set up a band above 10kHz to smooth the very top end of the cymbals.

With any element of a mix, multiband saturation can be an effective way of steering the energy of a track into a different frequency range in a way that is often not possible with EQ or compression. It can be used to help tame, or soften, guitars or synths too, and I often like to use a bit more of some tape‑style saturation around the 1‑3 kHz area whilst leaving the effect a bit more subtle elsewhere. With great power comes the distinct possibility of creating a real mess, though: as with any multiband processing, you really do need to apply it with care!

You should listen out for an excessive build‑up of energy in the low mid... especially if you’ve added multiple stages of saturation.

A Processing Primer

Despite the great advances in plug‑ins in recent years — which mean I’m happy to mix in the box — I do still observe a difference between studio hardware and software. With good‑quality outboard, I find that I can get a lot more assertive before things start to sound overcooked or bad. Happily, though, I find that saturation plug‑ins can be used as a sort of ‘primer’ that can make other plug‑in processors, particularly compressors and limiters, sound that little bit more forgiving. Using saturation on your kick and snare tracks, for example, can often round out the transients in quite a graceful way, and this can make any subsequent compression seem more consistent and natural‑sounding.

By smoothing out some the rough edges, it can also have the effect of making things feel more ‘seated’ in the mix, which can work particularly well on toms but also most other drum or percussive material. It’s also a good tactic with vocals. In fact, by pushing the effect a bit harder, the saturation can begin to do the job of compression on its own — it begins to level out the differences between the louder and quieter parts of a signal.

It’s a similar story with effects. Do you sometimes find that getting reverb or other time‑based effects to sit properly in a mix can be somewhat tricky? That they fight with the main sounds and you just can’t seem to place them at quite the right level, so you sometimes end up applying what feels like crazy amounts of EQ to get them to sit where they belong? This has often been a reason that I’ve deliberately created work for myself at the recording stage by printing dedicated effects tracks, using my analogue spring reverbs, guitar pedals or tape echoes. I like how these effects almost always seem to be set back deeper in the soundstage, and generally sound more ‘natural’ to my ears. Well, I’ve found that I can create a similar effect in software simply by using a saturation (or even an amp simulator) plug‑in either before or after a reverb or delay plug‑in. This can work especially well in those sparser productions in which you want to add a bit of ‘vibe’ or texture to a prominent part like a vocal or guitar, but still want to tread lightly when it comes to processing the main sound.

Placing a saturation plug‑in before time‑based effects like reverb can often make integrating the effect into the mix rather easier.Placing a saturation plug‑in before time‑based effects like reverb can often make integrating the effect into the mix rather easier.

Summing Up

Although saturation can be quite a tricky aspect of mixing to manage at times, it’s certainly one of the most fun and creative, and it has the potential to make a dramatic difference to your sound. Hopefully, I’ve given you a few ideas to explore in your own productions, but please don’t feel like you have to go out and splash the cash to do that — while there are certainly some wonderful paid plug‑ins out there, most DAWs offer some decent options to start out on your saturation adventures, and there are also some great free or inexpensive plug‑ins too. Whatever tools you choose, make a point of learning to hear what they’re doing and figuring out what you like and what you don’t. As I suggested above, while there are technical aspects to mixing, it’s always going to be your taste and judgement that sets you apart from other engineers.

Leave It Out?

While I use saturation often, I should point out that there’s a significant risk of overcooking it: I’ve heard more than one mastering engineer moan that everything they’re sent now sounds a bit distorted! I’m sure there are multiple reasons for that but am certain that saturation processors are one of them. I mean, I love a good ‘crunchy’ drum sound as much as the next engineer, but if it’s buried in a dense‑sounding production it can just seem weak and lacking in definition. Similarly, a mix’s bottom end can sound unfocused and all that ‘warmth’ can quickly congregate around the same low‑mid region, becoming ‘mud’ or ‘boxiness’. It’s also very easy to be seduced into believing that we’re capturing a vibe because of a plug‑in’s nice vintage‑looking GUI. There’s nothing wrong with a great GUI but the listener and client can’t see that stuff and, frankly, don’t care.

So remember that one of the most powerful engineering skills is being able to judge when something you’re doing isn’t adding anything positive! To help in that, consider making a point of bypassing a few plug‑ins as you get towards the end of a mix, to see if things might sound better with more of the transients poking through, or with more contrast between different parts of the song. You might end up leaving some bypassed, you might not — but it’s worth asking the question. And if you think a mix actually sounds better with no saturation tools at all, don’t be afraid to leave them all off.