Rocktron EN50082-1 User Manual download pdf (Page 15)

HUSH Function

HUSH

is Rocktron's patented single-ended noise reduction system. The HUSH

system contained in the Intellifex XL

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 ampli-

tude 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

Parameter Description

HUSH I/O

This parameter 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 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.

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Rocktron EN50082-1 User Manual Page 15

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