User manual ROCKTRON PROHUSH

[. . . ] This combination provides extremely effective noise reduction while playing and complete silence when not. Although the Super C is a stereo noise reduction system, a single HUSH Threshold and Gate Threshold are used to control both channels. This manual will introduce you to the various features and functions of the Super C. Please keep it for future reference. About the SSM2000. . . The SSM2000 is an advanced audio noise reduction system based on patented HUSH ® technology. [. . . ] The SSM2000 is commercially available from Analog Devices, produced under the license of the HUSH patents. HUSH ® combines a dynamic filter and downward expander to provide a high level effectiveness without the sonic artifacts normally associated with noise reduction systems. In addition, an Adaptive Threshold circuit detects nominal signal levels and dynamically adjusts both thresholds, thereby providing optimal results regardless of program source. Since it is a singleended system, HUSH can be used on virtually any audio source, including audio and video tapes, radio and television broadcasts, or any other source with objectionable noise. The SSM2000 can also be used with Dolby® encoded sources with excellent results. FEATURES: · Up to 25dB of noise reduction from virtually any audio source without sonic artifacts · External port available for additional attenuation-- providing in excess of 85dB of noise reduction · "Single-ended" operation eliminates need for encode-decode process · Adaptive threshold dynamically adjusts to changing nominal signal levels · Effectively decodes Dolby ® encoded sources · Direct VCA control port access for additional level control functionality · Logic-controllable bypass and muting · Flexible on-chip voltage reference · 100dB dynamic range (noise reduction OFF) · 0. 02% typical THD+N (@ 1kHz, noise reduction OFF) · +7V to +20V operation · No royalty requirements 1 OPERATING PRECAUTIONS NOTE: IT IS VERY IMPORTANT THAT YOU READ THIS SECTION TO PROVIDE YEARS OF TROUBLE FREE USE. All warnings on this equipment and in the operating instructions should be adhered to and all operating instructions should be followed. Care should be taken so that objects do not fall and liquids are not spilled into the unit through any openings. The power cord should be unplugged from the outlet when left unused for a long period of time. DO NOT MAKE ANY INTERNAL ADJUSTMENTS OR ADDITIONS TO THIS EQUIPMENT AT ANY TIME. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY VOID THE WARRANTY OF THIS EQUIPMENT, AS WELL AS CAUSING SHOCK HAZARD. POWER REQUIREMENTS This unit accepts power from the 9VAC/2A adaptor supplied with the unit. (The Gate Threshold control may also be used by itself, allowing the unit to be used as strictly a downward expander. ) HUSH® Section 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 Dynamic filtering is achieved by dynamically-controlling a low pass filter to open and close the bandwidth of the output signal depending upon the amount of mid and high band information present in the input 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). 7 This means that if a signal is present at the input which consists of primarily bass components, the dynamic filter will reduce mid or high band noise. If no mid or high band information is present, the filter will close down to a pre-set cut-off point of 1kHz (allowing only frequencies of 1kHz and below to pass). However, if the input signal has high frequency components present, the dynamic filter will open fully to pass the signal and eliminate the possibility of a loss of high end frequency response. Downward Expansion 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. When the input signal is above the user preset threshold point, the VCA circuit remains at unity gain. [. . . ] When the input signal is above the user preset threshold point, the VCA circuit remains at unity gain. (This means that the output signal level is equal to the input signal level. ) 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. 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 approximately 40dB (i. e. , 20dB of gain reduction). [. . . ]