Rocktron Intellipitch - Manual (Page 15)

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HUSH ® Function
HUSH ® is Rocktron's patented single-ended noise reduction system. The HUSH system contained in the
Intellipitch 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 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.
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, down-
ward 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 between -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 applications. For example, when using the expander for
gating applications on drums, a very quick release rate (25-200mS)
should be used. When used with individual 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.