Rocktron MultiValve - Manual (Page 21)

18
Functions and Parameter Descriptions
The HUSH ® function is accessible in all presets—regardless of the configuration
currently recalled.
HUSH is Hush Systems’ patented single-ended noise reduction system. The HUSH
system contained in the MultiValve is a fully digital implementation of HUSH achieved
through Digital Signal Processing (DSP), and is modeled after the latest HUSH design.
The low level expander of the HUSH system operates like an electronic volume
control. The analog version of the HUSH utilizes a voltage-controlled amplifier (VCA)
circuit which can control the gain between the input and the output from unity to 30, 40 or
even 50dB of gain reduction. When the input signal is above the user preset threshold
point, the VCA circuit remains at unity gain. (This means that the amplitude of the output
signal will be equal to that of the input signal.) As the input signal level drops below the
user preset threshold point, downward expansion begins. At this point the expander acts
like an electronic volume control and gradually begins to decrease the output signal level
relative to the input signal level. As the input signal drops further below the threshold
point, downward expansion increases. A drop in the input level by 20dB would cause the
output level to drop approximately 40dB (i.e., 20dB of gain reduction). In the absence of
any input signal, the expander will reduce the gain so that the noise floor becomes
inaudible.
The HUSH circuit is located after the A/D converter in the signal chain to reduce any
noise generated from the guitar, any guitar preamp and the A/D converter. This ensures a
quiet input signal to the MultiValve effects.
When the DIRECT HUSH parameter under the Mixer function is set to "Post", the
direct signal is passed through the HUSH circuit. When set to "Pre", the direct signal
remains analog and does not pass through the HUSH circuit.
The PARAMETER SELECT control will allow you to access each of the following
Hush parameters:
HUSH
Function
HUSH I/O
EXP THRESH
The HUSH I/O parameter determines whether the HUSH circuit is active
or bypassed for the current preset.
The EXPANDER THRESHOLD parameter determines the level at
which downward expansion begins. For example, if the EXPANDER
THRESHOLD was set at -20dB and the input signal dropped below
-20dB, downward expansion would begin.