Rocktron Chameleon On-Line - Manual (Page 19)

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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
Chameleon, 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 thresh-
old 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 approxi-
mately 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.
HUSH
®
Function
HUSH I/O
HUSH THRESH
The HUSH I/O parameter simply determines whether the HUSH® circuit is active for the
current preset.
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.
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 Chameleon 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 parameters: