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Learn Music and Audio Production | iZotope Tips and Tutorials

What Is an Ideal Mastering Signal Chain?

by Ian Stewart, iZotope Contributor November 17, 2021

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The mastering process is the final stage of audio production and one of the most crucial in achieving a professional sound. While there are many approaches to mastering a song from start to finish, in this article, we’re going to focus on the essential effects common in most mastering signal chains. 

In this article you’ll learn:

Follow along in your DAW

Create your mastering signal chain with Ozone Pro, included in a free trial of Music Production Suite Pro. Plus, explore custom presets, royalty-free sample packs, and mastering courses. 

What is a mastering signal chain?

A mastering signal chain is a series of processing effects applied to a signal in a linear order. Each signal process alters the signal for the next process in the chain, and so on. If you don’t think through the signal chain, you’ll likely need to add extra processing to compensate and “fight” against the chain’s upstream processing. Why fight it when all you might need to do is change the order a little?

How do you choose a mastering signal chain?

I’ve mentioned before that it pays to have a plan when mastering. Whether setting up a multiband compressor or an entire mastering chain, having a clear idea of what you want to achieve and how you’ll get there is key. Of course, along the way, you may uncover things or run across happy accidents that push you in a new direction, but having a strategy and goals that you can refer back to can be immensely helpful.

The way I like to approach this is to grab a notepad—digital or analog will do just fine—hit play, and only allow myself to take notes. No adding plug-ins or tweaking things, just set a comfortable volume, listen, and jot down the things that stand out. These could be overall tonal balance, potentially problematic dynamics, overly wide or narrow stereo imaging, odd noises or defects, or things I especially like and want to enhance. I’ll also want to be sure to include any specific notes or requests from the artist or producer!

Once you’ve compiled your list, take a minute to look at the big picture and start assigning tools to each of your goals. There are a lot of exotic and powerful tools out there, and they can certainly prove invaluable, but the truth is that most songs can be mastered with an EQ or two, the occasional compressor, and a limiter.

Learn to master these tools and how they work symbiotically in a chain first. Then, when you move on to processors like Low End Focus, Master Rebalance, or Spectral Shaper in Ozone Pro, they’ll be able to provide an additional level of control without muddying the waters.

Mastering processors and how you use them

Very broadly speaking you can categorize all mastering processors—and how you use them—into one of four categories. Understanding what these categories are and how they interact is probably the best way to sort out the order in which to build your chain for any given song.

Types of processing

Processors can be either linear or nonlinear, and they can be used either correctively or for sweetening. Let's break down these terms and define them.

Linear processors are ones for which the output signal is not dependent on the level of the input signal. In other words, whether the input signal is very loud, or very soft, the processor will do the same thing to it. Stereo imagers and most EQs are common examples of linear processors we use in mastering—although dynamic EQs or EQs which model the saturation of their analog counterparts do not fall into this category.

Non-linear processors are ones for which the output signal is dependent on the level of the input signal. In other words, the processor will react differently to a loud signal than it will to a soft one. Common examples of non-linear processors are things like compressors, limiters, and saturators.

The idea of corrective vs. sweetening moves is perhaps a little more intuitive, but to make sure we’re on the same page, let’s outline those too. Corrective moves are typically to remedy something  problematic in the source audio.This could be a buildup or hole at a specific frequency, an overly dynamic element in the mix, or a stereo imaging issue.

Sweetening moves, on the other hand, aim to enhance things we like about the source audio. Maybe that’s adding a little extra sheen to the top end, accentuating the stereo field for all, or part, of the frequency range, or some compression tailored to accentuate certain percussive elements or enhance movement.

Why it matters

So how do these concepts inform the order of your mastering signal chain? Let’s first think about corrective vs. sweetening moves.

Ideally, if you’re working with a great mix, you won’t need to make any corrections and you’ll be free to focus solely on sweetening and enhancement. From that perspective it’s easy to view corrective moves as a method to transform a good mix into a great mix that you can then focus on sweetening. Thus, most often it makes sense to do any corrective moves before ones aimed at sweetening.

What about linear vs non-linear processors then? In the sub-category of corrective use cases, I would say that 9 times out of 10 it makes sense to make linear corrections before non-linear ones. For example, imagine a song that has a big bass buildup along with a snare that’s poking out a little more than you would like, both things you’d like to adjust with corrective moves prior to sweetening.

You could start with a compressor to reign in the snare, but if there’s a ton of low end energy it could make the compressor pump or even distort in a way that you don’t want. By EQing first and tidying up the low end, you allow the compressor to more accurately focus on the snare as part of a well balanced signal. Conversely, as a linear processor an EQ will behave the same whether it comes before or after compression, so there’s no distinct advantage to compressing first.

When it comes to linear vs. non-linear sweetening moves the answer is less clear cut. Personally, I find myself preferring non-linear sweetening moves prior to linear ones a majority of the time, but it’s by no means a landslide. Experimentation can be key here. Don’t hesitate to swap the order and tweak your processing accordingly. Perhaps by EQing prior to saturation you need less overall saturation, or by EQing after you’ll need less high end sheen.

But enough of the theory! Let’s take a look at how to actually put these concepts to use by building an actual mastering chain.

Mastering signal chain example, from start to finish

Step 1: Limiting

Our example song today is going to be Caleb Hawley’s “Tell me What it’s Like to Have a Dream Come True.” To start, I’m going to add a limiter and adjust it to achieve something close to the final level I think I’d like for the song. I know I’ll probably come back and tweak this a bit, but since level affects our perception of tonal balance, it’s important to do our initial listen at a level not too far off from where we think we’d like to end up.

Here’s an excerpt with just some limiting. Have a listen, make some notes, and we’ll compare after the break. As always, good, full-range speakers or headphones are recommended.

Setting Levels with Limiting

Setting the desired level with some Ozone Pro limiting
Setting the desired level with some Ozone Pro limiting

What popped out to you? Here are my notes:

  • LOTS of low end, causing some distortion in the limiter and generally overpowering other elements.

  • The kick is poking out quite substantially compared to the bass.

  • The tambourine on every eighth beat feels just a little sharp or harsh.

  • I’d love to enhance some of the groove and movement.

  • The vocal performance is really lovely and tender. I’d love it to feel a bit less distant and more intimate.

Looking at this list, we can see that the first three points are more corrective, while the last two are aimed at enhancing or sweetening. Moreover, the first two notes are going to play off one another. Here, it definitely makes sense to start by getting the overall low end to sit in a more appropriate spot, so let’s do that. 

Step 2: Corrective EQ

Corrective EQ

Using corrective EQ with Ozone Pro
Using corrective EQ with Ozone Pro

As you can see—and hear—I’m carving out a few different areas in the low end to help with the overall balance. Already, things are feeling better, but that kick is definitely still poking out a lot, and we haven’t done anything up near that tambourine. Let’s tackle both of those with two bands of multiband compression.

Step 3: Corrective dynamics

Corrective Dynamics

Using corrective dynamics with Ozone Pro
Using corrective dynamics with Ozone Pro

There, that’s tucking in that kick just enough to tighten up the low end, and also smoothing out the tambourine just enough to keep it from feeling abrasive.

At this stage we’re ready to transition into some sweetening moves. I noted that I wanted to enhance the groove and movement, and for the vocal to feel a little more forward and intimate. I can achieve the latter with some EQ boosts in the midrange and top end, while the former will likely come from some wideband compression. I don’t necessarily want to boost the vocal presence into the EQ though, and risk triggering more compression off the vocal, so I’m going to start with some kind of gluey, groovy compression.

Step 4: Sweetening compression

Sweetening Compression

Using compression with Ozone Pro
Using sweetening compression with Ozone Pro

Yup, I’m liking that. Now that we’ve got that compression working, let’s go ahead and make some enhancements to a few key points in the vocal range. My goal is to enhance some of the little details in Caleb’s voice that you might hear more prominently if he were right up close to you.

Step 5: Sweetening EQ

Sweetening EQ

Using sweetening EQ in Ozone Pro
Using sweetening EQ in Ozone Pro

Ahhh, nice! I think we’re almost there. At this point I’m going to re-check our levels with Insight Pro, and revisit our limiter settings. Our levels are still looking good, but the limiter is working a little harder than I would like, and I’m also wondering if a touch of midrange warmth might be nice.

I’m going to try to take care of both these items at once using the Vintage Limiter module in Analog mode. It’s got a nice little midrange push, and can also soak up some level in a very euphonic way.

Step 6: Sweetening limiter

Sweetening Limiter: Final Mastered Sound

Using sweetening limiter in Ozone Pro
Using sweetening limiter in Ozone Pro

Sure enough, with a little tweaking that’s doing a really nice job! At this point I’m happy with my processing and I’m going to go ahead and print things. However there’s one more thing that’s part of my mastering chain on almost every single song: RX Pro for Music.

This isn’t quite part of the mastering chain in the same way that the other tools were, but there are almost always little clicks, pops, and ticks that surface throughout the course of mastering a song, and RX is by far the fastest and easiest way to quickly scan through and reduce or completely remove little artifacts like that.

Start mastering with optimal signal chains

So there you have it, my top tips for creating the ideal mastering signal chain for any song you work on. To recap, start by simply listening and making a strategy—writing notes helps! Then look at your notes and start to sort them into corrective vs. sweetening moves, and think about whether they will be achieved with linear or non-linear processors. Then, use the guidelines above to lay out an initial order based on processing type.

Of course, as always, never be afraid to experiment. You may find some cool processing interactions by switching up the order, but you can also easily end up fighting an uphill battle if processors start working against each other. If that happens, just remember you can always rewind and come back to these principles to work out the right chain for your song. Good luck, and happy mastering!

Learn more about mastering

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