TDK SA audio tape: a quick history
This is the TDK SA compact cassette, one of the most important audio tapes ever created.
The SA is considered the first non-Chrome Type II tape. It was designed to avoid paying royalties to DuPont, who developed Chromium Dioxide tape, but also to produce a competitive product cheaper, using existing production lines. By adding a small percentage of Cobalt to Ferric Oxide, TDK was able to mimic the characteristics of Chrome tape, including lower noise and better sensitivity in higher frequency range compared to regular ferric tape.
The SA required less bias current than true Chrome tape, which was important in 1970s, as many decks did not have a tape type switch, and even those that did could not provide bias current high enough needed for true Chrome tape.
This is a 1979 version, an improved one, and the one that has become a yardstick for all non-Chrome Type II cassettes.
This is a mid-1980s version, updated shell and updated tape. By this time the SA became so influential that the international standard, governing magnetic tape parameters, was updated to better match the SA.
This is a late 1980s version, a very contemporary design with textured shell, large window, and multispoke hubs.
This is an early 1990s version, a completely updated shell. The upscale SA-X and even the Metal MA used this shell, which was very rigid, heat-resistant, with smooth tape travel, a pinnacle of compact cassette development. It went downhill from here.
As cassettes gave way to CDs, and CDs then gave way to solid-state digital media, to downloads, and to streaming, research and development has stopped. TDK introduced “CDing” product line, that included CDing I and CDing II cassettes, for Type I and Type II respectively. The simplified shells were made of transparent plastic.
This was the point when cassettes stopped being objects of industrial art and became simply a recording media on its way to oblivion.
