Hush your hiss.
The Rocktron Hush Ultra processor's innovative digital stereo noise exterminator provides two channels of the same world-renowned professional noise reduction used for years in thousands and thousands of guitar rigs and recording studios. The Hush Ultra features True Bypass, an LCD display and programmable presets with MIDI control allowing you to tailor your Hush settings on individual presets to suit your needs. The Hush Ultra provides both 1/4" and XLR inputs and outputs, and is easy to setup and easy to use.
When used properly, the Rocktron Hush Ultra is completely transparent (i.e., it should not effect the audio signal—only the noise). The Hush Ultra front panel provides two controls which each manipulate both channels simultaneously. The Hush Threshold control sets the amount of noise reduction required for a given input signal, while the Gate Threshold control provides additional downward expansion when increased. (The Gate Threshold control may also be used by itself, allowing the unit to be used as strictly a downward expander.)
Rocktron's patented Hush noise reduction is a single-ended system that combines the principles of dynamic filtering and low-level downward expansion.
Dynamic filtering is achieved by dynamically-controlling a low-pass filter to open and close the bandwidth of the output signal. The filter bandwidth will only open far enough to pass the highest frequency information in the input signal, thus reducing the noise above it. For example, if the highest frequency present in the input signal is 8kHz, the filter will open to pass up to 8kHz while the noise from 8kHz to 20kHz would be reduced. If a signal with frequency components up to 20kHz appears at the input, the dynamic filter will open to its full extreme (40kHz).
The second half of the Hush process incorporates downward expansion. The low level expander of the Hush system operates like an electronic volume control. The Hush system 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. As the input signal level drops below the user preset threshold point, downward expansion begins. It is at this point that the expander acts like an electronic volume control and gradually begins to decrease the output signal level relative to the input signal level.