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 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 first led to the development of a sliding two-band compander by Ernst F. Schröder of Telefunken Grundlagenlaboratorium, Hannover since July 1974. However, the finally released High Com system, which was marketed by Telefunken since 1978, worked as a broadband 2:1:2 compander, achieving almost 15 dB of noise reduction for low and up to 20 dB RMS A-weighted for higher frequencies, while avoiding most of the acoustic problems observed with other high compression broadband companders such as EMT/NoiseBX, Burwen  or 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 mostly Dolby B-compatible compander as in the DNR (Dynamic Noise Reduction) system for backward compatibility. Consequently, second-generation tape decks with High Com incorporated a DNR expander as well, whereas in some late-generation Telefunken, ASC and Universum tape decks this even worked during recording, but was left undocumented. Nakamichi, one of the more than 25 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 assisted by Harron K. Appleman of Nakamichi in 1978/1979. The two-band variant was eventually released exclusively as Nakamichi High-Com II Noise Reduction System later in 1979, increasing the amount of noise reduction on analogue recordings and transmissions by as much as 25 dB A-weighted. While originally designed for tape recordings, Nakamichi demonstrated the usage of High Com II on vinyl records as well in 1979. In 1982 the same AEG-Telefunken team, who designed the High Com noise reduction system, also developed the IC U2141B for the CBS Laboratories CX noise reduction system for vinyl records. Similar to the earlier Dolby FM system in the US, a High Com FM system was evaluated in Germany between July 1979 and December 1981 by IRT. Based on the High Com broadband compander, it was field trialed between 1981 and 1984, but was never introduced commercially in FM broadcasting.