ALFAtron ALF-DSP88-U, Руководство пользователя

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ALF-DSP88-U
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3.3.3 Compressor & Limiter
Compressor
The compressor is used to reduce the dynamic range of the signal higher than the threshold set by the user, and to maintain
the dynamic range of the signal lower than the threshold. The compressor has the following control parameters:
Threshold: When the signal level is higher than the threshold, the compressor / limiter begins to reduce the gain. Any signal
that exceeds the threshold is regarded as overshoot signal, and its level will be reduced based on the ratio set. The more the
signal level exceeds the threshold, the more level is attenuated.
Ratio: It refers to the compression ratio. The ratio sets the attenuation degree of the overshoot signal to the threshold level.
The smaller the compression ratio is, the less compression will take place and signal will remain higher than the threshold.
Once the signal exceeds the threshold, the compression ratio decides the ratio of input signal variation to output signal
variation. For example, when the compression ratio is 1:2, if the input signal is 2dB higher than the threshold, the exceeding
part only changes by 1dB. A compression ratio of 1:1 suggests that the compressor does not attenuate the signal in
proportion. The adjustable range of compression ratio is 1-20.
Attack Time & Release Time: In order to maintain natural oscillation, it is generally accepted that part of the original level
will pass through the compression without any influence, or just minor influence. Likewise, if there is rapid sharp attenuation
and rapid recovery in the signal gain, the suction effect will occur. The attack and release time of the compressor is to avoid
this effect. The attack time sets the speed of gain attenuation, while the release time sets the speed of gain recovery.
Output Gain: Also called gain compensation. If the compressor significantly reduces the level of the signal, it may need to
enhance the output gain to maintain the volume. Output gain applies to all parts of the signal and is unrelated to other
parameter settings of the compressor.
Gain Reduction (G.R.) and output Level Meter: G.R. indicates the compressor's compression amount; output refers to the
output level of the signal that has passed through the compressor module (post compression). The compression amount is
displayed in an inverse level meter. If the input signal and threshold are set as -6dB and -30dB, respectively, and the ratio is
2:1, then the compression amount is 12dB; the G.R. level meter indicates around -12dB and output indicates around -18dB.