Avid Dynamic III Compressor

Threshold

The level at which compression begins. Signals above the threshold are compressed; signals below it pass unaffected. A lower threshold means compression engages earlier and affects more of the signal. For general dynamics control on guitar, start with the threshold set so that normal playing engages light compression while aggressive picking triggers more. On a modeler, setting the threshold too low compresses everything including quiet passages, which can reduce dynamic expression.

Ratio

The degree of compression applied once the signal exceeds the threshold. A 2:1 ratio means a 2dB input increase above threshold produces only 1dB of output increase — gentle compression. A 4:1 ratio is moderate. An 8:1 ratio is heavy compression. Above 10:1 effectively becomes limiting. For sustain and leveling on guitar, 3:1 to 6:1 is a common range. For limiting peaks, use 10:1 or higher.

Attack

How quickly compression engages after the signal exceeds the threshold. Fast attack (1–10ms) clamps down on the initial transient of each note — this reduces the 'pick click' and levels out attack aggressiveness. Slow attack (50–100ms+) lets the initial transient through before compression kicks in — this preserves the natural attack character of the note while controlling sustain. For guitar, slow to medium attack is generally preferable as it retains pick dynamics.

Release

How quickly compression disengages after the signal drops below the threshold. Fast release causes the compressor to 'pump' audibly as it chases the signal — this can create a rhythmic artifact that is sometimes musical (funk, country) and sometimes distracting. Slow release holds the compression longer, producing smoother, more transparent dynamics control. For most guitar and bass applications, medium to slow release (200–500ms) works well.

Gain

Make-up gain to compensate for the volume reduction caused by compression. Since compression reduces loud peaks, the overall apparent volume often drops — the Gain control restores it. Set Gain so that compressed and bypassed levels sound roughly equal when A/B testing.

Knee

Controls how abruptly compression engages when the signal crosses the threshold. Hard Knee means compression switches on immediately and precisely at the threshold — the transition from uncompressed to compressed is instant. This produces a more obvious, controlled compression character that is easy to hear and set precisely. Soft Knee means the compression gradually increases as the signal approaches and crosses the threshold — the onset is more gradual and the transition feels smoother and more natural. For most guitar and bass applications, Soft Knee produces a more transparent, musical result. Hard Knee is more appropriate when precise, audible limiting is the goal — preventing peaks rather than shaping dynamics.

Mode

Selects Compressor, Expander/Gate, or Limiter mode. Compressor mode: standard dynamics reduction above threshold. Expander/Gate mode: reduces signal level below threshold — useful for noise reduction between phrases. Limiter mode: hard ceiling that prevents the signal from exceeding the threshold, regardless of how loud the input is. In a modeler patch, Compressor mode is the most commonly useful for guitar and bass. Gate mode can help with noise reduction at the end of a signal chain.