Masters at Work: Channel Strip Mastering in your DAW

Something that regularly crops up is questions about demystifying mastering, and whilst I’m not the person to go into detail about exactly how to master your own music, there is a case for shining some light on the subject.

Mastering is sometimes seen as an Illuminati, secret hand-shake society of engineers unwilling to spill the beans on their secrets, and who’s to blame them really? With the relatively low cost of high-end plug-ins combined with diminishing budgets afforded to record labels, there is a trend towards home studio mastering, which is no doubt having a domino effect on people seeking professional mastering.

It’s a question that comes up over and over: Do I need to master my tracks?

Without going into too much detail about weather or not you should seek professional mastering if you’re serious about your music (hint: you should), it’s worth looking at some steps that can be taken to getting better master at home.

What this article will not be is a home mastering guide; not only is there (in my opinion) no substitute for people who know what they’re talking about, having proper acoustically treated rooms, an excellent signal path and wealth of experience, but there’s also pages and pages of stuff on the internet already written about the subject matter, which I don’t want to contribute to.

This isn’t meant to replace professional mastering, but having a more comprehensive understanding of what happens can not only improve your own productions and mixdowns but might give you a better idea of what you need to do in order to prepare your tracks for mastering.

To confirm, I am not suggesting you can’t do good mastering at home, it’s just not something I’m going to talk about here. This is merely a discussion about what goes on my master channel strip, some of which is there to help monitor what’s going on, some of which is there to colour the sound and some of which is there as a reference.

So, with that in mind, let’s crack on with what actually is mastering.

So What is Mastering?

Mastering is the final process a track passes through before it’s distributed en masse. This can include getting the track to a competitive commercial level, homogenizing tracks produced or recorded in different studios and generally tidying up rogue frequency spikes.

JM Mastering has this to say about it:

Mastering is the art/science of assembling individual songs into cohesive musical excellence and should be considered the final step in a recording project before going into manufacture. Mastering gives your music the means to compete in the world of commercially released material. We level the playing field by bringing your recordings to their fullest potential, whether you recorded it at home, or spent thousands of pounds at a recording studio.

Future Music made this video (using a pal of mine’s track), demonstrating what happens in a commercial mastering session.

Sometimes the project or label won’t have the budget for professional mastering, or you may be required to submit a home master as a demo, or you might just need to know how things are going to sound like mastered in order to proceed with the mix.

Whilst I’m not going to divulge into the pros and cons of home mastering here, there is certainly a case for properly understanding the process.

Natural Order

Before moving on to what constitutes my master channel strip it’s worth mentioning the order of things. Although we’re going to deal with some of the visual and imagining tools first, these would need to be last in the chain.

This is because you want to see the effect of any plug-ins you’ve added. For example a certain type of tape saturation might dull the high end a little, or particular compressors may add harmonics etc. It’s important to see how these effects are changing the frequency spectrum, transients and phase information.

Visual Aid

Regular readers of the blog will know that we’re huge fans of Voxengo SPAN, and this would be the first thing on my list of desert island plug-ins. As a spectral analyser it’s not unique (Live and Logic both offer alternatives) but it’s free, highly customizable, has the option to freeze frame snapshots and change the display colour, resolution and decay rate. Did I mention it’s free?

Keeping your frequency spectrum in check is a must for me. This is not to act as a substitute for your ears but as an auxiliary tool. If you’re unfamiliar with spectral analysis, have a read of this.

Another necessity is Bram @ Smartelectronix.com’ s(M)exoscope (pronounced exoscope I recently learnt). This is an oscilloscope, normally confined to useage in a laboratory or  sound design studio but I find it hugely useful for monitoring my transients and keeping them in check.

Sadly it’s 32-bit only, but with a half decent 64-bit plug-in wrapper (like 32 Lives) then you can run it in a 64-bit environment like Logic X. Luckily it is now 64-bit!

Imaging Heap

With our transients and frequencies all nice and tidy, there are some other imaging tools we can turn our attention to. Logic X has a handy MultiMeter plug-in that covers a few bases. This is a spectral analyser (albeit not quite as resolute as SPAN) but it shows us a few other things too.

Highlighted in red is the level meter, however it’s a little more advanced than the ordinary one in Logic’s mixer. The darker blue represents the peak level (or loudest peak the sound reaches), whereas the lighter blue is the RMS (equating to perceived volume, or musical energy).

Producer, YouTuber and all-round good egg Monte has an excellent video explaining the difference between these two levels:

Getting your RMS signal close to your peaks will mean you can squeeze more volume out of your music without audible distortion. Ableton Live’s latest update now includes peak and RMS metering as standard, which is a very welcomed addition to the DAW. I’m going to be covering peak and RMS in much more detail at a later stage so keep an eye out.

Back to the MultiMeter, highlighted in green is a phase correlation meter which measures the phase relationship of a stereo signal. When the meter is reading +1 it means we have an in-phase signal. Anything that veers towards 0 means there is some degree of phase cancellation (no pun intended).

To my knowledge, Ableton doesn’t offer something to check for this in its native bundle, but there are various Max4Live options available.

You can test this by duplicating an audio track. When both are played at the same time, the volume is twice as loud. If we were to invert the polarity of one, although both would appear to be metering, the output would be 0 as they are cancelling each other out. I will also be covering this topic in more depth at a later stage.

If you’re unclear on phase and polarity, YouTuber Matt Mayfield Music has great video that explains it brilliantly:

Mono-lith

Having a good, strong mono image is as important in mastering as it is in mixing. Whilst there’s a plethora of plug-ins available to widen our sounds with various time based tricks, these can play havoc when summing to mono.

The phase correlation meters mentioned above will be an important tool in checking the nuances of phase correlation, but a sure-fire way to check with just your ears is mono-ising your track. Some soundcards have a mono button (like mine for example) but simply putting a plug-in in the chain will also do the trick.

Logic X has the Gain plug-in equipped with a Mono button and Ableton Live has the Utility in-which you can bring the Width down to 0%. I have them enabled all the time but have the plug-in bypassed, then, when I want to check my mono sum, I can un-bypass them.

Magic A/B

Sound design company Sample Magic have come up with an awesome referencing plug-in: Magic A/B. This allows you to load up to six tracks, loop them and flick between your own material (A) and the references (B) quickly and without hassle, latency or any of the problems commonly associated with A/B-ing within your DAW.

Here’s mix engineer legend Dave Pensado reviewing it for his YouTube Pensado’s Place channel:

I can’t stress enough how important it is to check your work against commercial records when mixing and mastering, and this plug-in has made it a breeze. At £35 it’s a bargain too, so worth getting your hands on it.

Compression

Once we’ve got our metering plug-ins in place, you might want to think about compressing the mix. I want to reiterate; this isn’t a guide to mastering your own music. You may be required by mastering engineers to disable any master channel effects you have, others might only ask you disable any limiting.

I mix into a limiter (more on this later) which I will always disable when providing a pre-master for the client/label (unless the label has asked for my master because a smaller budget, for example). However there are a few other plug-ins that are lightly colouring the mix. One of those would be some compression.

I will go into discussion about compression in later articles, but for now a laypersons guide to compression is this: compression is like an automatic attenuator for your track. The key components are threshold (where the signal is compressed) and ratio (by how much).

With mastering, I wouldn’t very rarely compress the track too much, and for this reason I would normally select a low ratio (say 2:1 or similar), and have the threshold set to just catch the peaks of my music, lightly tickling the gain reduction meter.

I’m not really a huge fan of the native plug-ins in Logic and Live for these purposes, so normally opt for the SSL G-Master Buss Compressor, but that’s more personal preference rather than a benchmark.

There are of course other parameters and I don’t want to try and over-simply compression so I’m going to leave it here and suggest you research the topic some more if you decide to go down this route. Bobby Owsinski’s blog offers some great tips for setting attack and release times.

There are occasions where I might need to compress the bass more than the mid range or vice versa, and might sometimes opt for multi-band compression in this scenario. However, assuming it’s my own music and I still have access to the stems this is pretty rare.

In the off chance I am mastering for someone else this can be the case (no access to stems) and then the FabFilter Pro-MB is my go-to multiband compressor.

Other Mastering Plugins

Aside from compression that are other plug-ins I might use in a creative manner rather than a corrective one. Depending on what music I’m working on these can include but not be exclusive to tape saturation (PSP Vintage Warmer 2 is a favourite of mine, but I understand why lots of people don’t get on with it), passive EQs (Waves PuigTec EQ EQP-1A is my go-to), and sometimes graphic EQ (like the Waves API 560), but each track brings different requirements, and the best mastering engineers will react to the music rather than by fixed in their ways.

Some people are fans of using mid-side EQs (such as FabFilter’s Pro-Q 2). Again when working with my own music I usually have a great deal of control of the stems/busses so have never found the need to reach for this, but others like to high-pass filter the sides. You can read more about EQing in general here.

One last process I like to do before hitting my limiter is send my mix out of the computers into some hardware and print the recording back in. My hardware setup is limited at my home studio but I get a half-decent sound out of my TL Audio Ivory 2 5060.

I don’t like the compression circuit in this, so I just use the input gain to drive the valves lightly. This is by no means a mandatory step but it’s something I feel helps glue the track together. To read more about using external hardware with Logic and Live, have a read of this.

Limitless

Although this article has been written in a seemingly odd order, the last audio effect in my chain before the imaging/metering plug-ins would be my limiter. I have stuck by the Waves L2, and it seems popular with others too. I don’t know why this is, but what I look for in a limiter is transparency, especially when applying (sometimes) up to 6 or 7 dBs of gain.

For a more aggressive sound I like iZotope Ozone, as this allows you to change the algorithm of how it deals with clipping, from transparent to distortion which can be useful in more pumping masters like DnB. I’ve only got an aged copy of Ozone (version 5) and I understand they have made many changes to later releases including standalone mode where other plug-ins can be loaded into the engine, which sounds fantastic.

Ozone comes with some other processes too such as multiband compression, a multiband exciter (useful for brightening up dull mids and high-end when EQ doesn’t sound right) and mastering reverb, although I don’t use any of these too often.

Mastering for Vinyl

I thought it would be useful to include something about mastering for vinyl. This is certainly a case where you would need to leave it to the professionals as there’s all sorts of potential complications with stereo information jogging needs to the length of tracks compared to the overall volume you can cut to the lacquer.

ReSoundSound have written a very comprehensive article on cutting vinyl and the mixing/mastering considerations you need to know, which you can read here.

My Channel Strip

To finish off I’ll show you a typical mastering strip I used for the last thing I finished that was mastered by someone else. I sent off two copies of this, one with all of the mastering effects disabled and one with just the limiter disabled, with the former being used.

To explain my thought process a little: PSP Vintage Warmer is used to help glue the tracks together, it ever so slightly dulls the top end (not too much) and adds a small amount of harmonic distortion. The PuigTec EQP-1A is bringing out a little bit of high-end – again, nothing drastic because I’m not here to change my mix, just sweeten it a bit. The SSL Bus Comp is having it’s GR meter just tickled by the transients, this again helps to solidify the sounds together.

My I/O plug-in is running out of outputs 3-4 into my TL Audio 5060 where I adjusted the input gain to hit the valves at a pleasing level to me. This changes significantly depending on the source material, but in this instance I could hit it fairly hard before it started breaking up. Once I found the threshold I just reigned it in a notch or two. I also enabled the ‘FAT EQ’ switch on the output of this, which adds a 2dB boost at 50 Hz, a 1dB dip at 720 Hz and a 2dB boost at 10 kHz.

Next I run into the L2 where I’m limiting at -0.3dB and adding about 7dB of gain. Due to the transparent nature of the L2 I seem to be able to get away with quite a bit of limiting without significant audio degradation. After this is Magic A/B to check my already limited track against my references. Then SPAN to check my frequencies are all doing what they should be and I’ve not missed anything my ears couldn’t detect, s(M)exoscope to check my transients aren’t too crushed and finally the MultiMeter to observe my phase correlation and over-all RMS level.

I hope this had shed some light on master channel strips. For me, the takeaway message is more about the imaging/metering plug-ins I use rather than the compression or EQs, which can be very subjective. Metering and imaging plug-ins are no substitute for your ears but they can be a useful auxiliary.

Finally, always check with the client, label or mastering engineer if you’re unsure what you should be delivering to them and that it has enough of a dynamic range.