Nilfisk-ALTO BK 2.0 - Manual (Page 7)

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2.1.4 More about noise: Expanders and Noise-Gates
A lot of instruments such as microphones, amplifiers, guitar pickups, etc generate some noise, either at low frequ-
encies (hum) or at high frequencies (hiss) Such noise will inevitably interfere with the quality of your audio signal.
Now, if you scream into a microphone you will not hear the noise generated by such microphone because such
noise will be "masked" by the higher level of the signal, your voice in this case.
But if you sing into your microphone more gently in a soft passage, the level of the signal generated by your voice
will get much closer to the floor noise level and such floor noise will become disturbing. In order to kill this problem
Expanders and noise-gates are used. An expander is the opposite of a compressor: attenuating the signal when the
amplitude drops they can limit the floor noise.
Now, we do not need dramatic expansion of a signal across the range, This would generate a resulting dynamic
range of over 150dB. For this reason the amplitude control will be applied only to those audio signals which are
below a set threshold. Those audio signals above the set threshold will not be affected. Noise-gate can be regarded
as a simple Expander. But the Expander will attenuate the audio signal continuously below the set threshold while
the noise-gate will simply dramatically cut-off the audio signal completely.
2.2 Voltage Controlled Amplifier (VCA)
The VCA is the soul of the BK 2.0 and it is one of the best components available today in his category thanks to its excellent
performances in terms of distortion, linearity, noise and temperature stability.
2.3 Inputs
2.3.1 Take it easy: Balanced Inputs
To make your life easy and clean we have provided BK 2.0 with electronically balanced inputs. Even if you
operate at high signal levels, hum and noise will be reduce automatically. There is also a servo-function that will
automatically adjust the internal level when unbalanced connectors are detected. The correction if of 6dB and
it will avoid differences in level in between input and output signal.
3. CONTROLS
Pic.1: Front panel layout of the BK 2.0
EXP / GATE COMPRESSOR / LIMITER ENHANCER
THRESHOLD THRESHOLD RATIO ATTACK AUTO RELEASE OUTPUT IN/OUT PROCESS
dBu dBu n:1 ms dB EFFECT IN CLOSE
OFF +10
-70 0
-50 -15
-30
-40 +20
-30 +10
-20 0
-10
1 LIM
1.5 8
2 5
2.5
0.1 200
1 150
10 100
50
50m 4
0.1 2
0.3 1
0.5
OFF 6
1 5
2 4
3
-20 +20
-14 +14
-6 +6
0
EXP / GATE
THRESHOLD
dBu
CLOSE
OFF +10
-70 0
-50 -15
-30
-30
ON
OFF
POWER
CH1
CH2
AUTO CH1 IN AUTO CH2 IN
30 20 15 10 6 4 2 1
GAIN REDUCTION (dB)
R LTO COMPRESSOR
/LIMITER/GATE
BK2.0
COMPRESSOR / LIMITER ENHANCER
THRESHOLD RATIO ATTACK AUTO RELEASE OUTPUT IN/OUT PROCESS
dBu n:1 ms dB EFFECT IN
-40 +20
+10
-20 0
-10
1 LIM
1.5 8
2 5
2.5
0.1 200
1 150
10 100
50
50m 4
0.1 2
0.3 1
0.5
OFF 6
1 5
2 4
3
-20 +20
-14 +14
-6 +6
0
The BK 2.0 presents with right and left channels. Each channel is equipped with the same control elements: 2 push-button
switches, 7 rotary controls and 11 LED's.
3.1 Expander/Gate Section
Pic.2: Controls of Expander/Gate section
1 2
EXP / GATE
THRESHOLD
dBu
CLOSE
OFF +10
-70 0
-50 -15
-30
-30
1.Threshold Control
This control adjust the threshold level for the Expander / Gate Section in the range of Off to +10dBu. Signals
below this level cause attenuation.