Yamaha CS1D Owner's Manual - Page 543

Compressor Types Compressor Types Dynamics processors are generally used to correct or control signal levels, although they can also be used creatively to shape a sound's volume envelope. The following sections explain the COMP, EXPANDER, and COMPANDER-(H/S) compressor, their parameters, and general applications. Output Level (dB) Output Level (dB) COMP The COMP processor is a compressor that attenuates signals above a specified threshold, providing automatic level control. Vocalists that tend to move toward and away from the microphone while singing produce fluctuating signal levels; sometimes loud, sometimes soft. Likewise, acoustic instruments with a large dynamic range produce sound levels from pianissimo (very soft) through to fortissimo (very loud). In these situations, it is often difficult to set an average fader level that will allow a voice or instrument to be heard clearly throughout a song or piece of music. This is where the compressor comes in with automatic level control. By automatically reducing 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 signal-to-noise performance. [Compressor] +20 +10 Compression ratio = 2:1 0 -10 Threshold = -20dB -20 -30 Knee = Hard -40 -50 -60 -70 -70 -60 -50 -40 -30 -20 -10 0 +10 +20 Input Level (dB) The COMP processor can also be used as a limiter, which is essentially a compressor with a high ratio setting. Compression ratios above 10:1 are considered to limit signals rather than compress them. When an input signal exceeds the specified threshold level, its level is automatically reduced to the threshold level. This means that the limiter's output level never actually exceeds the threshold level. Limiters are often used to prevent signals from overloading amplifiers and tape recorders. A limiter with a relatively high threshold, for example, could be used with the stereo outputs to prevent amplifier and speaker overload. [Limiter] +20 +10 Compression ratio = 20:1 0 -10 Threshold = -20dB -20 -30 Knee = Hard -40 -50 -60 -70 -70 -60 -50 -40 -30 -20 -10 0 +10 +20 Input Level (dB) Parameter Range THRESHOLD -54 dB to 0 dB (1 dB steps) OUT GAIN ±0.0 dB to +18.0 dB (0.5 dB steps) KNEE HARD, SOFT 1, SOFT 2, SOFT 3, SOFT 4, SOFT 5 ATTACK 0-120 ms (1 ms steps) RELEASE 5 ms-42.3 s (fs = 48 kHz) 6 ms-46 s (fs = 44.1 kHz) RATIO 1:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 8:1, 10:1, 20:1, ∞:1 (16 points) INPUT FILTER HPF (high-pass filter) or HPF/LPF LPF (low-pass filter) INPUT FILTER ON/OFF ON or OFF INPUT FILTER FREQUENCY 20 Hz-20 kHz (121 steps) THRESHOLD-This determines the level of input signal required to trigger the compressor. Signals at a level below the threshold pass through the compressor unaffected. Signals at and above the threshold level are compressed by the amount specified using the Ratio parameter. The trigger signal is sourced using the KEY IN parameter. OUT GAIN-This sets the compressor's output signal level, and can be used to compensate for the overall level change caused by the compression process. 11