Rocktron VooDu Valve Online User Manual page 19

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 Voodu Valve, though modeled after the latest analog HUSH
design, is a fully digital implementation achieved through Digital Signal Processing
(DSP).
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 and the A/D converter. This ensures a quiet input signal
to the preamp section. Because the preamp section of the Voodu Valve™ is digital, it is
virtually noise-free (even in the high-gain mode). Therefore, a quiet input signal to the
preamp will result in a quiet output signal.
The PARAMETER SELECT control will allow you to access these Hush
HUSH I/O The HUSH I/O parameter simply determines whether the HUSH®
circuit is active for the current preset.
HUSH THRESH The HUSH THRESHOLD parameter determines the level at which
downward expansion begins. For example, if the HUSH THRESHOLD
was set at -20dB and the input signal dropped below -20dB, downward
expansion would begin.
®
parameters: