All of Logic's audio channel strips have a level meter that displays the channel's volume in decibels (dB). The bottom of this meter represents a dB value of (that is, silence), while the top of the meter represents 0 dB, which is the maximum allowable volume level before the signal clips the channel. As the level meter pulses up and down, the peak level is held for a few seconds, so you have time to see its value. The numerical value of the peak level is also displayed in the clip detector at the top of the level meter. With this in mind, lets take a moment to explore what clipping really means.
Clipping occurs when too much signal is fed through a channel. Clipped audio sounds fuzzy and distortedyou certainly don't want clipped audio in your song. Fortunately, you don't have to rely on your ears alone. All audio channels have a clip detector that shows you when the channel is in danger of clipping.
The clip detector is above an audio channel's level meter. When too much signal is fed into the channel, this detector turns red to tell you that it's time to turn down the volume. Furthermore, once a channel clips, the clip detector stays on until you turn it off by clicking anywhere on the channel's level meter.
Because Logic uses 32-bit floating-point processing for all internal calculations, you can actually clip Logic's internal audio channels a little bit without creating distortion in your final mix. However, as soon as the audio leaves Logic through an output channel, you must be sure it peaks no higher than 0 dB. This is a very important concept, so let's create an output track in the Arrange window and use that channel to explore clipping.
If an audio channel clips, the clip detector remains on until you manually turn it off.
Reverting a Slider to Its Default Setting
The Out 1-2 channel strip's volume level is set to +6. Let's revert it to 0 using a handy trick: In Logic, Option-clicking a slider or a knob always returns it to its default setting. This works not only for the channel strip, but also for all Audio Instrument and effects plug-ins.
Adjusting Volume Levels
Under normal conditions the clip detector is off, and the numerical value it displays shows you the amount of headroom left above the channel's most recent volume peak. Headroom means the number of dB left before the channel clips. For example, if the clip detector is off (the background is brown), and the number it displays is 4.9, the channel can be raised a maximum of 4.9 dB before the audio clips. As you saw in the last exercise, when the clip detector turns red, the channel's audio has clipped, exceeding 0 dB. In this situation, the number printed in the clip detector shows you the number of dB over 0 at which the channel has peaked, which in turn is exactly the number of dB by which the track needs to be attenuated, or reduced, in order to avoid clipping.
Let's use the Out 1-2 channel's level meter to adjust the volume of the Output 1-2 Object so that it comes as close as possible to 0 dB without clipping the channel.