Limiting is the simplest of techniques used in reducing dynamic range. When amplifying or recording a signal with the wide dynamic range of a guitar, simply setting the volume control so that the loudest peaks do not cause distortion may not be satisfactory. The quietest parts of the guitar might disappear in a mix and the sound may lack punch. Often vocals also suffer in this way. Limiters and compressors alter a signal so that there is less volume difference between the highest and lowest parts. Ensuring that the full range is heard, these devices also give a recorded sound more impact. They are both creative and corrective tools.

 

A limiter not only reduces the dynamic range but also is useful when high peaks are generated which, if uncontrolled, may cause damage to hearing, loudspeakers, and other equipment. Limiting is also the basis on which automatic volume and recording level controls function. The limiter is simply an amplification stage which has variable gain, controlled by a circuit that senses the level of the incoming signal.

 

The gain of the limiter is linear until the input signal rises above a determined level. When the sensing circuitry detects this it instantly reduces the gain so that the output level remains constant. The level at which the gain change occurs is called the "threshold". Most limiters have a control allowing this level to be set.

 

When the input signal falls below the threshold once again, the gain of the amplifier returns to its original level. The "release" control governs how quickly this happens. It should be set so that it causes the minimum disturbance to the sound of the music (distortion may become evident at high speeds, when the limiter has the least apparent effect on signal dynamics). If the release time is extended beyond five seconds, the limiter will operate as an automatic level control.