iZotope RX Mastering Tips

10 Common Uses for Audio Restoration in Mastering

4. Removing unwanted distortion Every once and a while you get a project that has audible distortion. It could be undesirable clipping, or it could be something else entirely. All you know, from your vantage point, is that the distortion is undesirable to you.

But it might not be undesirable to the band. Your first move is to call the point person on the production team and ask if that distortion is intended. If it isn’t, your next move is to contact the engineer, if you can, and negotiate a better mix. This option isn’t always on the table, so luckily software like RX has ways to fight this distortion—tools which can, to some extent, repair mangled material.

A lot of the time the De-clip module does the trick, even if the material isn’t clipping per se. The process is relatively simple: highlight the passage that is distorting, have the module suggest its processing, audition the results, and tinker to taste.

Repairing distortion is best done in specific, sporadic places, and not across passages of more than a couple of seconds—and that’s speaking liberally. You may have to spend a bit of time to get all the nasty bits, but it’s still worth it.

Sometimes, the distortion is more of a high-end crackle than a clip. Here, the De-crackle module, tuned to attenuate high-frequency distortions, can often work.

I have a very particular live performance in mind. Recorded a guitar (DI) that was using some form of distortion — pedal or amp, not sure. Unfortunately detracts from some of the songs, can’t really remove the guitar. My case isn’t mastering, I have an isolated track. Need to try the “De-crackle” and “De-clip”. The track(s) don’t clip. Challenging.

Applying in practice. As I suspected the De-clip module doesn’t touch the distorted audio. The clipping got recorded at about -12 dB soooo.

De-crackle made a nice dent in the scratchy top-end of the distortion. Basically maxed out the settings, soloed the crackles, made things better. Nice to know.