Sansui Super Feedforward System
A Guide to the Sansui Super Feedforward System
The history of Hi-Fi amps began in 1947 with the introduction of the Williamson amplifier, the first amp to reduce distortion effectively by using the NFB theory. The Williamson amp. in fact, became a reference amp by which later amps were judged.
There followed a series of new amp designs Tube amps gave way to transistor designs, output-transformer-less amps went output-capacitor-less. and finally, DC amps replaced AC models. Throughout this progression, new devices to reduce distortion still further proliferated. The NFB technique, however, remained indispensable It is no exaggeration to say that there would be no Hi-Fi amps today were it not for its application. It has been proven so effective that almost all amps on the market today make use of it.
Despite its ubiquity, however, NFB is limited in its effectiveness against distortion The NFB technique. as it has been used, cannot achieve 100% reduction of distortion no matter how refined or elaborate its application.
To accomplish this goal, Sansui had to find a breakthrough as startlingly new and different as the Williamson amp was in its time. We accomplished this with the Super Feedforward System. Feedforward theory actually dates back as far as 1928, when it was developed by H.S Black. Although it has long been applied in highly advanced communications systems, efforts to find Hi-Fi audio applications met with no success - until Sansui came up with a unique and untried solution to the problems the technique posed.
We did it by combining, for the first time in audio history, NFB and feedforward techniques. As excited members of the Audio Engineering Society (AES) were first told at a convention in London in February, 1980 (and again in Los Angeles in May of the same year). the Sansui Super Feedforward System has reduced all types of distortion - total harmonic intermodulation, switching, crossover and envelope to zero. Hi-Fi amplifiers will never be the same again.
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