Yamaha AW4416 Reference Guide - Page 160

Appendix Compressor Output Level dB A compressor provides a form of automatic level control. By attenuating +20 +10 Compression ratio = 2:1 0 -10 Threshold = -20dB -20 -30 Knee = hard high levels, thus effectively reducing the dynamic range, the compressor makes it much easier to control signals and set appropriate fader levels. Reducing the dynamic range also means that recording levels can be set higher, therefore improving the signal-to-noise performance. -40 -50 Compressor (CMP) parameters: -60 -70 dB Parameter -70 -60 -50 -40 -30 -20 -10 0 +10 +20 Input Level Threshold (dB) -54 to 0 Value (55 points) Ratio 1.0, 1.1, 1.3, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 8.0, 10, 20, ∞ (16 points) Attack (ms) 0 to 120 (121 points) Outgain (dB) 0 to +18 (36 points) Knee Release (ms) hard,1,2,3,4,5 5 ms to 42.3 sec*1, 6 ms to 46.0 sec*2, 8 ms to 63.4 sec*3 (6 points) (160 points) *1. These values are obtained when the sampling frequency is 48 kHz. *2. These values are obtained when the sampling frequency is 44.1 kHz. *3. These values are obtained when the sampling frequency is 32 kHz Threshold determines the level of input signal required to trigger the compressor. Signals at a level below the threshold pass through unaffected. Signals at and above the threshold level are compressed by the amount specified using the Ratio parameter. The trigger signal is determined using the KEY IN parameter. Ratio controls the amount of compression-the change in output signal level relative to change in input signal level. With a 2:1 ratio, for example, a 10 dB change in input level (above the threshold) results in a 5 dB change in output level. For a 5:1 ratio, a 10 dB change in input level (above the threshold) results in a 2 dB change in output level. Attack controls how soon the signal is compressed once the compressor has been triggered. With a fast attack time, the signal is compressed almost immediately. With a slow attack time, the initial transient of a sound passes through unaffected. Out Gain sets the compressor's output signal level. Compression tends to reduce the average signal level. Out Gain can be used to counter this level reduction and set an appropriate level for the next stage in the audio path. Knee sets the transition of the signal at the threshold. With a hard knee, the transition between uncompressed and compressed signal is immediate. With the softest knee, knee5, the transition starts before the signal reaches the threshold and gradually ends above the threshold. Release determines how soon the compressor returns to its normal gain once the trigger signal level drops below the threshold. If the release time is too short, the gain will recover too quickly causing level pumping-noticeable gain fluctuations. If it is set too long, the compressor may not have time to recover before the next high level signal appears, and it will be compressed incorrectly. 25 - Reference Guide Appendix-