Project "Phoenix"
HITACHI CASSETTE DECK D-2200M
HUSH Noise Reduction System by Analog Devices SSM2000
The SSM2000 is an advanced audio noise reduction system based on proprietary HUSH® circuitry. HUSH combines a dynamic filter and downward expander to provide a high level of 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 pro-gram source. Since it is a single-ended 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 be used with Dolby encoded sources with excellent results. A key feature is direct access to the Voltage Controlled Amplifier port enabling additional functions such as dc volume control, automatic level compression, etc. with minimal external circuitry.
The HUSH board (Circled in Yellow) and Auxiliary Switch Relay Board for Logic for my BIAS Tune Semi Auto System (Circled in Magenta).
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Conclusion
I totally rebuilt this deck from scratches. Only main board left original with DOLBY B/C circuits and improved first stage amplifiers (MPSA18 ultra low noise transistors).
DOLBY HX PRO with new BIAS Generator was added
New Power Supply was added
HUSH Noise Reduction System was added
VU Display was redesigned
Semi Auto BIAS Tune up System was added
Recording Amplifier and Final stage Amplifier was redesigned (TL082)
Main Control Logic Processor was rebuilt (reverse engineering) on TTL Logic Chips.
How it is working?
Really great! This is the best deck for old tapes recorded without Dolby Noise reduction system. It really takes advantage of HUSH Noise Reductor really better than other Dynamic filters like DNR or Dolby B. Super hard Glass-Ferrite Heads last forever.
That was totally crazy project.
I wouldn't do it again but I enjoyed spending my free time on this and that counts. That was good learning experience.
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