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Gain Staging: What It Is and How to Do It

by Nick Messitte, iZotope Contributor March 7, 2019

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Gain staging—a term that baffles many beginners. It’s the kind of phrase people throw around at producer parties (mixing mixers?) as though they know what it means. Often they don’t.

Even if I threw down a prosaic definition of gain staging—say, “adjusting the level at each point of amplification to ensure an optimal signal-to-noise ratio, without unwanted distortion”—it might only confuse you, especially if you didn’t understand the building blocks of that definition.

So in this article, we’ll cover those building blocks. Furthermore, we’ll cover a modern approach to gain staging, one that defies the analog rules of yesteryear.

Now, before we defy those rules, we need to define them, so we know how to go about acting differently. First we’ll talk about analog gain staging, then we’ll talk early digital, and after that, we’ll cover the glories of our modern epoch.

Gain staging in the analog days

Before the advent of digital, records were made with analog equipment. Microphones, outboard EQs, compressors, console desks, tape machines—every piece of gear had to be leveled properly for the next piece of the chain, in order to achieve a good result.

Now, a good result could mean something pristinely clean, or something pleasantly saturated; this depended on the material in question.

There were issues in getting these good results: go for something too quiet, and you’d approach the noise-floor (a blanket of constant, audible hiss that, if present in the overall mix, would be distracting). That’s why a good signal-to-noise ratio would be critical—you wanted more signal and less noise.

On the other hand, push the gear too hard, and you’d incur unusable distortion. This was usually the result driving a unit beyond the capability of its power supply’s voltage.

Now we can circle back to that definition to see if it makes more sense.

In the analog world especially, gain staging refers to adjusting the level at each point of amplification to ensure an optimal signal-to-noise ratio, without (unusable) distortion.

You had to think globally, across the whole chain of gear. Overdrive one piece and sure, it might sound good in a vacuum. But the combination of a bunch of processes all driven too hard could overwhelm the final result of a track—or negatively impact the whole mix, which is the combination of many tracks.

Here we come across terms like “headroom” and “noise-floor.” You don’t want to be hovering too close to the noise-floor; you want to drown it out. But you also want to leave enough headroom. You need a buffer or safety zone that can accommodate transient spikes or loud moments without causing horrible distortion.

And that’s how it was in the days of analog—greatly simplified, of course.

Gain staging in the dog days of digital

Digital systems always had an “analogue” to analog—a similar, though not identical point of no return: It’s called 0 dBFS (0 decibels full scale), and it describes the highest possible level in the digital world you can achieve without clipping (incurring terrible distortion).

Digital clipping sounds really, really bad most of the time. It can be used as an effect, but that’s outside the scope of this article, and certainly outside the bounds of this section.

Respecting and fearing 0 dBFS was the norm of great “in the box” mixing in the days of early digital. In practice, reverence for the digital ceiling looked relatively simple—at least, for the common mortal who didn’t want to get too deep into mathematical concepts: just treat the process as you did in the analog world. General guidelines included:

  • Positioning the faders of a static mix below unity gain, and aiming to avoid going higher than 0 on the faders whenever possible (assuming the tracks were recorded at a good level).
  • Making sure no individual channel-fader was positioned above its corresponding submix’s fader position (to avoid even the possibility of driving anything too hard)
  • Making sure no individual channel ever set off your DAW’s horrendous red meter—the one that signifies clipping
  • Making sure no analog-modelled plug-in was driven past the point of pleasant, harmonic distortion
  • Making sure no digital, non-analog equivalent plug-in clipped within the module, as that could cause unwanted distortion

Those were the days of fixed-point—the days when crossing the digital ceiling marked a fixed point of no return; the audio would always be degraded in some way, which I will illustrate in a moment with audio examples.

One by one, however, DAW and plug-in developers alike turned to floating-point processing, and now we find ourselves in a new reality.

Gain staging in the present

Most DAWs currently operate with floating-point processing, often 32-bit or 64-bit. This allows for handling audio in ways unthinkable in the days of analog, and impossible in fixed-point digital systems.

I shall not get into the mathematics or the science; if that interests you, I’ll leave it for deeper reading in Bob Katz’s book. Instead, I’ll show you examples of what happens when you push beyond the point of no return, so you can see the power of the floating-point world.

Here is a test tone feeding a bus. It hovers at -14 LU on the Insight meters, as you can see.

Test Tone Feeding a Bus

I don’t have an ancient copy of a DAW floating around, but I can take the test tone, boost it up beyond 0 dBFS, and export it as a 16-bit file. Then, I can bring it back into the DAW and show you what it sounds like level-matched to the unaffected test tone.

Reads the same on the meter, right? But let’s hear how it sounds.

Digital Distortion on Test Tone

That’s some digital distortion right there. It’s fundamentally different from the original test tone, and it sounds bad.

Let’s start again: I often use Logic Pro, a floating-point DAW. So, if I were to raise the original test tone beyond 0 dBFS, it would certainly look like it’s clipping on the meters—but check this out: the test tone has been routed to a bus. If I were to bring this bus down on the fader, I can get it to sound like the original, undistorted test tone.

What do we get?

Test Tone +24: -24

In case you were wondering if it really matches the original test tone, here’s a file proving they null down (cancel out) to an inaudible level.

Null Test Tone

Null test tone

But what does it all mean?

We’ve basically demonstrated that in the domain of floating-point, you can push above 0 dBFS and not harm the signal, so long as you dip back down on the track’s corresponding destination. This is all before you export it as a fixed-point file (a CD-quality WAV file, for instance), or before you send it through a D/A converter—do keep that in mind, or else you’ll incur distortion.

But what does this mean for you, the mixing engineer?

Simply put, freedom! A freedom to move faders around in ways unthinkable in the olden days—so long as certain conditions are met without exception.

Say you’ve got a drum mix you like—the balance is great; the processing sound awesome—but the drums push the whole mix into the red. Say, furthermore, that you’ve got a compressor you really like on the drum buss, so you don’t want to change how you drive it. You’ve got options for how to treat the problem, including:

  • Turning down the master bus
  • Turning down the fader of the drum bus
  • Putting a utility plug-in after the compressor and turning that down
  • Sending the drum bus to another bus and turning that bus down

The result of these methods will get you to similar places, but each has its own benefits and drawbacks:

Option 1, turning down the master bus: 

This will get you different results depending on the DAW. Say you’re in Logic; if you have processing on the master bus, you’ll still be hitting that processing at the higher, pre-fader levels, which may or may not be what you want (more on this later). If you’re using Pro Tools, you might have the bus configured on a master fader. This means turning the master fader down will affect the processing because the fader drives the level into the processing. Confusing, isn’t it? The other options are less confusing.

Option 2, turning down the fader of the drum bus:

This may affect how the drums hit any processing on the master bus. It also may be super-annoying to turn down a fader with a bunch of automation already written for it.

Option 3, attenuating the plug-in’s output:

With this method, you can turn down the track without affecting fader automation. Heck, you can automate the plug-in down at specific moments where you’re hitting the digital ceiling—micro adjustments that only affect the sound for milliseconds, yet save you from clipping upon export!

Option 4, setting up a new, intermediary bus:

What this gives you are different ballistics for automation from the previous option (depending on the DAW and the plug-in, of course). The output of some plug-ins, for example, can move in 0.01 dB increments, which can be either helpful or annoying, depending on what you need. Logic’s fader, on the other hand, only moves in 0.1 dB increments, which may help or hinder you.

That may seem overwhelming, but it’s also very, very freeing. It means that when it comes to gain staging inside the box, you can actually think outside the box.

Certain conditions apply

We mentioned a moment ago that certain conditions must be met without exception for everything to work. Here they are:

Some classic plug-ins still operate in fixed-point.

As you’ll find vintage hardware pieces, you’ll also come across older plug-ins often revered for their sound. These modules could very well employ fixed-point data plotting, simply because they are old! It pays to do research on your old favorites, or better yet, to update to floating-bit versions where available; I have affection for an analog clipping emulator whose logo hails from the Jurassic age. I could, on my system, run the fixed-point version. But I upgraded so I wouldn’t have to worry about it.

Some plug-ins model analog hardware—to a fault!

This fault would be the point of analog distortion. If you’re using an analog modeler and you’re pushing it too hard, it will still sound distorted, even if you lower a corresponding bus fader. Sometimes this is what you want—sometimes this is why you employed the plug-in. Other times, however, you wanted this at the beginning of your mix, but by the end of the process, a horrid noise trips you up; such distortion could very well be the culprit.

If you’re bringing down the output of a limited buss or track, it will still sound limited.

The rules of squashing dynamic range still apply in this crazy floating-point world. So it still pays to watch your inputs and outputs, as we did in the days of analog. Does this have anything to do with clipping against the digital ceiling? Not really. But if you offer your mastering engineers a file well below 0 dBFS and still sounds limited, there’s little they can do to give it more life.

Make sure the output of the master bus doesn’t hit 0 dBFS.

This is very important, because in the analog world, because a fixed-point file is still the bottleneck for a tune you’ll stream on Spotify or sell on CD. As of March 2019, the output of the final file has to play nicely in the fixed-point world to work with delivery media. Who knows, this may change, but right now them’s the rules.

Conclusion

We could obviously go deeper and deeper—and longer and longer—into gain staging, but this is enough to get you familiar with the subject. Plus, that list of considerations will surely come in handy

So the next time you’re at a music meet-and-great and fellow mixers sling around terms like gain staging, noise-floor, and headroom, you’ll have a better idea of what they mean. Of course, now that you know, you can skip the party altogether and get back to what really matters: a vibrant mix, one that you control at every level. The stage is now yours to gain!

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