High Com

The High Com (also as HIGH COM, both written with a thin space) noise reduction system was developed by Telefunken, Germany, in the 1970s as a high quality high compression analogue compander for audio recordings.

The idea of a compander for consumer devices was based on studies of a fixed two-band compander by Jürgen Wermuth of AEG-Telefunken ELA, Wolfenbüttel, developer of the Telefunken telcom c4 () four-band audio compander for professional use. In April 1974, the resulting "RUSW-200" prototype led to the development of a sliding two-band compander by Ernst F. Schröder of Telefunken Grundlagenlaboratorium, Hannover since July 1974. Finally, the released High Com system, which was marketed by Telefunken since 1978, worked as a broadband 2:1:2 compander, achieving around 10 dB of noise reduction for low and up to 20 dB A-weighted for higher frequencies, while avoiding most of the acoustic problems observed with other high compression broadband companders such as dbx.

In order to facilitate cost-effective mass-production in consumer devices such as cassette decks, the compander system was integrated into an analogue IC, TFK U401B / U401BG / U401BR, developed by Dietrich Höppner and Kurt Hintzmann of AEG-Telefunken Halbleiterwerk, Heilbronn. With minimal changes in the external circuitry the IC could also be used to emulate a Dolby B-compatible expander as in the DNR (Dynamic Noise Reduction) system for backward compatibility.

Nakamichi, one of the more than 20 licensees of the High Com system, supported the development of a noise reduction system that could exceed the capabilities of the then-prevalent Dolby B-type system. However, it became apparent that a single-band compander without sliding-band technology, which was protected by Dolby patents, suffered too many audible artifacts. So High Com was further developed into the two-band High Com II and three-band High Com III 2:1:2 systems by Werner Scholz and Ernst F. Schröder of Telefunken and Harron K. Appleman of Nakamichi in 1978/1979. This variant was eventually released as Nakamichi High-Com II Noise Reduction System in 1979/1980, increasing the amount of noise reduction on analogue recordings and transmissions by as much as 25 dB A-weighted.

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