by Bruce Bartlett
(1) When I record myself or our band, I’m clipping the waveform even though I’m not exceeding 0 dB at the top of the level meter. What’s going on?
Reply: Make sure to set your record meters and playback meters to read peak levels, not RMS levels. The peak levels show how close the signal is to clipping. The RMS levels show approximately how loud the signal is. Peak levels are always higher than RMS levels. So, if your record level reaches -1 dB in RMS meter mode, it might actually be over zero (clipping) in peak meter mode.
You might be clipping the mic preamps in your audio interface. Set the interface gain knobs on the loudest notes so the interface’s clip lights don’t flash. If you are recording a loud instrument with a condenser mic, switch in the mic’s pad (if it has one) to prevent distortion in the microphone itself.
(2) Should I insert a compressor plug-in to prevent clipping?
Reply: You don’t have to. Just turn down the gain on your audio interface. Use conservative recording levels, like -6 dB maximum in peak meter mode. That way, when you add more gain from plug-ins, you are less likely to clip the signal. Also, aiming for -6 dB maximum prevents accidental Overs.
(3) I’m touching up my recording levels with the DAW faders, but they don’t seem to be doing anything.
Reply: They aren’t! The faders affect only the monitor levels and mix levels. The gain knobs in your audio interface set the recording levels.
HOW TO AVOID CLIPPING DURING MIXDOWN
I know to avoid “overs” or clipping when recording, and I usually keep my recording levels slightly below the red. But what about AFTER I’ve recorded and am mixing down? Many tracks are clipping, and so is the stereo mix bus. I’m tired of using compressors to avoid pegging the meters.
Reply: Compressors are not meant to prevent clipping, faders are. During mixdown, no fader should go above 0. You might start a mix with all the faders at -12 (see the figure), then go from there.
If you recorded a track just below clipping, then you raise its fader above 0, that adds gain which makes the track clip. So start with all the faders low, like -12. Leave the master faders (in the mixing console view) at 0 dB. Then you can bring up the volume of certain tracks without running into clipping. Same for volume envelopes… stay below 0 dB maximum unless the signal is so low that boosting it causes no clipping.
A boost in an equalizer raises the signal level at the frequencies you boosted, potentially causing clipping. So watch the meters in your equalizer plug-in. When you apply a boost, if the track starts to clip, turn down the equalizer gain if it has that feature. If not, turn down the track trim to prevent clipping the equalizer. The track trim control affects the level going into the equalizer.
During a mixdown, all the tracks are summed or combined before they feed into the stereo mix bus. The more tracks you mix together, the higher the level of the combined signals. Even if each track does not exceed 0 dB level, the combined level of the mixed tracks can easily go above 0 dB, causing clipping in the stereo mix bus. That’s another reason to keep the track faders fairly low, so that the stereo mix bus doesn’t overload.
In the mixing console view, usually at the far right, are the stereo output master faders and meters. Keep those faders at 0. If the stereo mix level is getting too high, turn down all the track faders by the same amount. That prevents clipping the stereo mix bus. The maximum meter reading of the complete mix should reach about -3 dB, but it’s not too critical.
Some DAWs are designed so that the stereo mix bus cannot be overloaded. In that case you can touch up the master fader levels. If the stereo mix level starts to exceed 0 dB, bring down the two master faders below 0 until the meter reads about -3 dB maximum. That prevents clipping the output of your audio inteface.
Bruce Bartlett is a recording engineer and microphone engineer (www.bartlettaudio.com). His most recent books are “Practical Recording Techniques 6th Ed.” and “Recording Music On Location.”