The Compressor - Schippmann ebbe und flut User Manual

8.2 The Compressor

The compressor provides the frontpanel components [compression] (3) and [slow/fast] (4) and the
socket "DIST OUT" (21) on the rearpanel.
For better understanding of the compressor, we will have a look on its basic functionality. A compres-
sor "recognizes" the level of its input signal and is capable to follow fast transients, e.g. of a kickdrum.
This is done by a so called detector, which derives a voltage, analog to the current signal level.
This information about the current signal level is used to control the dynamics of this signal. Compres-
sion means, that a certain change in level at the input, leads to a reduced change in level at the output.
The so called compression rate is the quotient or ratio between input level change in [db] and output
level change in [db].
A rate of "2" means that the output level rises/falls with 10 db, while the input level has been rising/
falling with 20 db.
In case you are planning to become an expert, we would like to distinguish between some technical
terms:
The Amplitude of a signal is equivalent to its maximum peak-to-peak amount. It is measured in Volts.
The effective level of a signal is also a unit of measurement for its energy-amount. It depends from its
specific waveform and is also measured in Volts.
The level of a signal is the logarithmic ratio-quantity with effective quantity refered to a reference va-
lue. From this ratio, the logarithm is taken and measured in decibel.
front: (3) [compression]
The compression rate is mostly named ratio. This can be adjusted over a wide range with the knob
[compression] (3).
Another important parameter is the so called threshold or knee point of the compressor. It determines
the level, at which the compression starts to work, resp. higher levels are reduced in dynamics. Thres-
hold is also controlled with the [compression] (3) knob.
A third parameter is the output level of the compressor. When a low threshold is chosen (e.g. -20 dbu)
in connection with a high ratio (e.g. 20), the output level would hardly exceed a level of -20 dbu. In
order to avoid this reduction in level resp. restore the original level, an overall amplification (of e.g.
+20 dbu) is added. This level is also controlled by the [compression] (3) knob.
Fig. 8.2.1 shows what happens when the [compression]-knob (3) is turned clockwise.
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