Managing Distortion

/November 15, 2014
How do you avoid your mixes sounding like they’ve been shoved through the intake manifold of a 747’s jet engine? Watch out for distortion from day one of your recording session.
In the last couple of years (even longer probably) more songs than ever seem to have been released with an almost lethal dose of harmonic distortion. It’s gotten so bad in fact that many new songs sound like they’ve been printed with their white noise calibration channels accidentally feeding into the stereo mix bus. To make matters worse, many radio stations also seem to be adding their own layer of this brutal, unmusical hash to the body of their broadcast mixes – nice.

Of course, this isn’t what’s actually happening – well not yet anyway – only what appears to be. Either way it’s not good. Too much distortion is being applied to all facets of audio production and the outcome is all too often an indistinct, harsh yet soupy mess, masquerading as professional mixing. Pretty soon there won’t be any musical content left in some of these releases, only white (and various other coloured varieties of) noise – whole musical genres in the making.
The problem is that most distortion embedded in final masters is the direct result of processes that were never intended to generate it in the first place. And with look-ahead limiters dominating the digital outputs of most productions, plug-ins by the dray load on every channel of a mix, and poorly calibrated systems the norm amongst studios and home setups, it’s no wonder.

The main thing to be aware of – if it’s not your intention for your folk/rock song to sound like was recorded near the approach runway of Sydney airport – is that distortion is insidious, cumulative and increases exponentially once compressors and limiters get involved. In other words, it’s easy for distortion to creep up on you and take over a mix if you’re not looking out for it, but only slightly more difficult to keep your music relatively free of it, if that’s your preference.
The trick is to judge how much distortion is appropriate early on, whilst remaining cognisant of the fact that whatever percentages of distortion you record now will only increase as the production gets mixed, mastered and converted to various shoddy forms of MP3.

There are obvious problems at the end of any production, where mastering can potentially inject a lethal dose of distortion into the process, particularly if you ask the mastering engineer to make your record ‘loud’, when right throughout the rest of the process you’ve been banging on about ‘preserving the dynamic’. But it must also be noted that what often appears to be mastering distortion was, in fact, generated well beforehand in the early stages of recording. Mastering may only have magnified what was already there (while adding extra distortion on top for good measure).
As with any music involving the recording of real instruments, it all starts with source sounds. While the expectation for many of these is that they be captured distortion-free, some will obviously contain an amount of distortion, large or small, that was well intentioned. Electric guitars, for instance, may be built fairly and squarely around their distortion characteristic; a classical flute on the other hand…
Regardless, a judgement needs to be made during tracking about the degree to which the captured instruments should sound distorted. It may only be subtle in these initial stages, but now is the time to remind yourself that once inherent distortion is embedded on a recording, it’s only going to be magnified by the production process – it will never diminish. So if you want your recording to be relatively distortion-free, now is not the time to be adding it by accident.

One of the most insidious ways distortion is generated during recording is at the microphone preamp – and it’s one of my greatest bugbears.
The problem arises when a recording system is poorly calibrated so that when the recording level on the digital recorder is looking relatively high, at say –10 or even –5dBFS, the analogue mic preamp feeding it is getting a flogging, at say +10 to +20dBu.
For many analogue preamps, a higher than optimum output level quickly compromises the clarity of the sound passing through it, sometimes without the engineer or others involved even being aware, let alone concerned, about it. (And unfortunately, many preamps don’t even have an output VU meter). People simply look at the meters on their digital recorders and assume that ‘high’ levels are ‘good’ levels, regardless of how they’re generated. But it’s supremely ironic that many of these so-called ‘healthy’ digital recording levels are actually achieved by thrashing the analogue preamp stage as the engineer simultaneously tries to achieve a quiet, distortion-free digital level. It’s engineering gone bonkers!

It’s critically important to calibrate your recording chains before you start a session (or at least be aware of what they are), so that 0dBu on your analogue VU meters measures a known digital input level – somewhere between say –20 and –14dBFS (unless of course it’s analogue tape). That way, when your analogue front-end gear is running at its optimum, the digital recording device is too. Remember, if you’re recording 24-bit files, it’s completely unnecessary to try and push your recording levels to the brink of the digital ceiling.

There are countless other processes along the way that add further distortion to your final product: channel compressors, mix bus limiters, multiband compressors and so on, not to mention the countless recording and mixing plug-ins that intentionally distort a signal. But most of these can be ditched if things are getting out of hand. This is not the case when you add distortion to recorded material unintentionally. Once it’s printed, there’s no cleaning it up.
We all know how to add distortion, particularly during mixing – that’s easy. But when you’re tracking, be vigilant throughout the process, listen with your ears, not your eyes, and remember that any subtle amounts of distortion may turn out to be far too much by the time your mix hits the airwaves.