Nilfisk-ALTO BK 2.0 - Manual (Page 12)

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5. INSTALLATION AND CONNECTION
5.1 Mains Connection
BK 2.0 is provided with dual voltage plug. You must check the power supply Voltage available in your
Country before connecting the power cord in the wall outlet. Please see Page, paragraph 12 for further info.
5.2 Audio connection
The BK 2.0 Compressor/Limiter/Gate is equipped with balanced XLR connectors as well as 1/4" pho ne jack and can
be connected with other units in different ways to support a vast range of applications without experiencing a signal
loss.
4.2.8 Gain Reduction Meter
This consists of 8 LED on the front of the BK 2.0. Through this Led meter you can visualise the amount of gain reduction
at any given time.
Chart.6: The effect of a compressor can be expressed as the amount
of gain reduction that is taking place for any given input
4.3 Limiter Section
How fast is the compressor to react to a signal which is above the threshold point? This is determined by the
attack time. A longer attack time is advisable to process low frequencies while shorter attack time is preferable
for high frequencies. IN this way you will avoid undesired dynamic distortion. But what about if you are mixing
a program with a wide range of frequencies? In this case you should choose a setting that would benefit the
low frequency better.
Well, life is not that easy for conventional compressor/limiters. Ok you handle an audio signal made by a wide
range of frequencies and you have chosen a longer attack time. But, if are using your BK 2.0 as a limiter the
fast high frequencies will pass through untouched because the attack time is too slow and such transients could
cause distortion when the unit is connected to broadcast devices or taper recorders.
The solution in BK 2.0 is represented by our Smart Gain Control (SGC) limiter circuit. The curve in bold is the
output signal and the dashed curve above it is the input signal. The area in between the two is the amount of
gain reduction.
The unit will activate the limiter when the signal exceeds the threshold for more than 15 microseconds. Then 1
second after that the signal is below threshold again, reduction goes back to 0dB and in this case input and
output signals are again identical.
Chart.7: SGC characteristic of the limiter section
Peak Limiting
6ms 15ms
Level
Program Limiting
Input
Release
Output
approx. 1 s
Threshold
t/ms
30 20 10