What Is Soft Saturation and How Is It Used?

This article references previous versions of Ozone and Neutron. Learn about the latest Ozone and its powerful new features like Master Rebalance, Low End Focus, and improved Tonal Balance Control by clicking here, and learn more about Neutron 4 by clicking here. 

You may have noticed Neutron 3’s EQ sports a parameter called “soft saturation.” The effect is subtle—if your ears aren’t catching it, you may not be sure what it’s doing. Soft saturation is meant to give you something akin to analog warmth. But how does soft saturation achieve this feat? Moreover, how and when should you use soft saturation?

Read on to find out!

What is soft saturation?

Located in the top right of the EQ’s GUI, soft saturation adds harmonic excitement to the signal. It’s not like the exciter however, which tries to emulate tubes, tape, and other sounds. This excitement is fashioned on a classic British console equalizer—and we must linger here on the nature of console equalizers. 

Never forget that Neutron 3 is like a channel strip, and channel strips boast a proud heritage, stemming from the large format consoles that housed them. In a channel strip, you’d usually find a preamp, an EQ, an input trim, and a polarity switching control. Some also sported built-in compressors and gates. Whatever they had, channel strips could dominate your toolbox during the mix, especially if you didn’t have outboard gear available for patching into the desk.

What does soft saturation have to do with analog console EQs?

Much in the way certain DAWs are more popular than others—or dare I say, certain plug-ins drown out the competition—some large format consoles rose to prominence. It’s a broad simplification to say that Neve, API, and SSL consoles occupied this top-tier status in the latter quarter of the 20th century; that leaves out many different, wonderful consoles (Helios, Harrison, EMI, and Trident, to name a few).  But Neve, API, and SSL were all recognized for the different ways they’d treat audio, their different workflows and timbres. An engineer might love or hate their individual sounds—but they would nevertheless recognize each one.

Much like hardware compressors, analog EQs could be simple or complex in their construction; they could utilize different operating principles. Some sported transistors, others tubes. Some utilized integrated circuits, while others completely eschewed them. 

Every design philosophy resulted in a recognizably different sound, and a different feel as well. From here stem the generalizations: APIs are often called “forward” and “punchy”, handling sound sources up to 30 dBm without any distortion; Neves are labelled as “creamy”, with an inherently “sweet” sound; SSLs are “exact”, “clean”, and “clinical”. I’ve heard them called “swiss army knives” with a “crisp” sound. 

All of these descriptors are merely words until you hear a console EQ for yourself, whereupon you’d make your own judgments. And your judgments are inherently personal.

Less personal are the measure of an EQ’s curves, its phase response, or its generation of harmonic distortion. These phenomena can be observed and quantified. When you put a Neve, an API, an SSL—or any other hardware EQ—under the metaphorical microscope, you’ll see varying responses in your measurements. This becomes the scientific qualification of what we mean when we say a device has its own sound.

And now, back to Neutron 3’s soft saturation, with a more defined context: never forget that Neutron 3 is like a channel strip. It’s made of math and offers sonorous bells and whistles—but it’s still a channel strip, meant to be used as a workhorse on all your tracks. If you want to add the flavor of analog circuitry, soft saturation lets you do that in a way reminiscent of classic hardware. 

Let’s have a look under the microscope.

Here’s a sine wave at 1 kHz, with a not-so-subtle 10.5 dB boost at 1 kHz. I’ve juiced the input to make the measurements easy to see, and brought down the output to make it bearable to hear. No soft saturation has been applied.

And here are the same settings with soft saturation engaged.

You can hear the grainy difference between the two, but let’s analyze what we’re seeing in the GUI. Here it is without soft saturation:

And here it is with soft saturation:

Clearly, we’re seeing harmonics up the chain, around 2 kHz, 3 kHz, 5 kHz, 7 kHz, 9 kHz, and so on. These are sympathetic resonances composed of musical intervals up the scale. However, there’s more going on under the hood, and to see it, we’ll load up our trusty plug-in doctor.

Here’s what flat (no processing) looks like without soft saturation:

And here’s what happens if we put on soft saturation at a flat setting.

Wow. Already we’re seeing sculpting—a roll-off around 50 Hz, a bump extending between 50 and 100 Hz, an overall drop in level of a dB, and so on.

This means when we turn on soft saturation, we’re already working into a filter—we’re pushing into a prism of sound. To look at it, you’d think it wouldn’t work for something like a bass instrument. However, look at some bass boosts, at 30 and 100 Hz respectively.

More than enough low end going on here. We’re also seeing an interesting phase and dynamic response. Here’s the phase response of the EQ, without soft saturation.

If you’re unfamiliar with how an EQ affects the phase response of a given band, let’s just say this: analog EQs always change the phase relationships of the sound they’re slapped on—and usually this is a pleasurable change, hence the desirable status of many EQs. Digital EQs can either change the phase relationships, or adopt a linear phase approach, which preserves them. 

We’re at flat settings here, so we’re seeing no change in the phase. This makes sense—Neutron 3 doesn’t offer a linear phase EQ (for that, check out Ozone), but leave its settings untouched, and it imparts no phase shift whatsoever. 

The flat settings of soft saturation, however, already focus the sound through a filter, as shown above. So the following result shouldn’t be surprising: