Rocktron Intellifex LTD - Manual (Page 24)

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HUSH ® PARAMETERS
Hush I/O
This parameter simply determines whether the HUSH ® circuit will be in the
signal path or bypassed.
Exp Thresh
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.
Typically, this parameter should be set between 5-20dB above the quiescent
noise floor of the input signal (i.e. if the noise floor was -60dB, a setting be-
tween -40 and -55dB will produce the proper expansion).
Rel Rate
The Release Rate parameter determines the amount of time required for the
downward expander to decrease the level of the output signal. This rate is
adjustable from 25mS to 800mS to accommodate a wide variety of applica-
tions. For example, when using the expander for gating applications on drums,
a very quick release rate (25-200mS) should be used. When used with indi-
vidual instruments such as guitar, a setting of 200mS or higher will provide
adequate expansion without being as harsh as a gate. When used with sources
which have long decay times (cymbals, etc.) a very slow release rate should be
used.
F. HUSH ® SECTION
HUSH ® is Hush Systems’ patented single-ended noise reduction system. The HUSH ® system contained in the
Intellifex LTD is Hush Systems' first fully digital implementation of HUSH achieved through Digital Signal Process-
ing (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 design
utilizes a voltage-controlled amplifier (VCA) circuit which can control the gain between the input and 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 is 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 amplitude drops below the user preset threshold point, downward expansion begins. At
this point the expander operates like an electronic volume control and gradually begins to decrease the output
signal level relative to the input signal level. For example, if the input signal were to drop below the threshold
point by 2dB, the output would drop approximately 3dB. As the input signal drops further below the threshold
point, downward expansion increases. For example, if the input signal dropped 6dB below the threshold point, the
output level would drop by approximately 14dB. A drop in the input level by 20dB would cause the output level
to drop by approximately 54dB (i.e. 34dB of gain reduction). In the absence of any input signal, the expander will
reduce the gain such that the noise floor becomes inaudible.