Nilfisk-ALTO BK 2.0 - Manual (Page 10)

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4. READY TO ROLL?
4.1 Expander/Gate Section
Chart.3: Function of an expander
As we told you previously in this Manual the downward expander will reduce automatically the level of the audio signal when
such signal is below a set threshold. So the expander is the opposite of the compressor/limiter. We also explained to you how
the ratio curve of the expander is flat while a noise gate it is more brutal processor: It simply cut-off the entire signal below a
certain set threshold. The BK 2.0 is equipped with a new kind of expander, the SRC (Smart Ratio Control). The ratio of the
SRC is automatically adjusted according to the audio signal level. In fact, conventional expanders could easily cut part of the
musical program with unacceptable result:The gain changes become audible.
We have equipped the SRC with a non-linear ratio curve, which is soft and adjustable by the User. Thanks to the SRC low
passages close to noise floor level will be processed with a minute ratio of expansion while for signals of reduced level a higher
ratio will be used with resultant greater attenuation.
Chart.4: SRC Curve characteristics of the Adaptive Expander
4.1.1 Threshold Adjustment
The threshold control covers a very wide range and it is efficient with any working level. Turn the threshold control
fully counterclockwise and the Expander/Gate section will be completely off.
4.2 Compressor Section
4.2.1 Another Threshold Control?
The compressor threshold control sets the point where the input level starts to be reduced. Let's say the level is
+12dBu and the threshold control is set at +2dBu: In this case up to 10 dB can be compressed. If the input level
is the same and the control is set at 10dBu the maximum compression will be 22 dB, The operating range of the
threshold control is -40 to +20dBu. Turn the threshold control fully clockwise and you will get a threshold level of
+20dBu.
You must remember that the degree and the type of compression not only depend by the threshold control but
also by other controls such as Ratio, Attack and Release.
SRC CURVE