Clipping is a particularly nasty form of distortion that occurs in the digital domain when the level of the audio signal moves above 0dB – into the red. Because there’s no more space to describe the waveform, we instead get a truncation…
Keeping It Down
The first thing for ensuring your track doesn’t clip (presuming of course that there was no clipping on the input stages of capturing the waveform in the first place) is to make use of the available headroom – bring the faders down.
If you’re running 24-bit tracks, then you have 144dB of headroom to play with. At the mixing stage, there’s no need to be anywhere near the red. Bring the faders down, and turn your monitors up if you must, but don’t feel you have to keep your peaks towards the top of the meter.
If you want to make the record loud, you can do that after the mixing has been completed. However, it’s a good idea to maximise to somewhere just short of 0dB – the general recommendation is to go for -0.3 dB as the ceiling.
This will help guard against variations in how different CD players reproduce the audio, and also guard against inter-sample peaks. In a digital recording, it’s possible to have two contiguous samples at a maxed-out 0dB full-scale, and it won’t register as clipping – however, when this is converted to analogue, the curve will peak between these samples, and rise slightly above 0dB, creating a small clipping artefact. This may or may not be actually audible, but in a 24-bit domain, there’s really no need to have any clipping at all… so take things down a notch…!