The
RCA
RCA Corporation was a major American electronics company, which was founded in 1919 as the Radio Corporation of America. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westinghou ...
Type 77-A microphone was a
simplex
In geometry, a simplex (plural: simplexes or simplices) is a generalization of the notion of a triangle or tetrahedron to arbitrary dimensions. The simplex is so-named because it represents the simplest possible polytope in any given dimension. ...
(''uni-directional'')
ribbon microphone
A ribbon microphone, also known as a ribbon velocity microphone, is a type of microphone that uses a thin aluminum, duraluminum or nanofilm of electrically conductive ribbon placed between the poles of a magnet to produce a voltage by electroma ...
, the forerunner of the
RCA Type 77-DX microphone. The 77-A was designed
Dr. Harry F. Olson in the late 1920s or early 1930s; prototypes are rumored to have existed in 1929 and 1930, but the 77-A was not announced until 1932.
The 77-A would set the standard for all other RCA ribbon microphone comparisons for the next 40 years.
Construction
It featured a spiral acoustic labyrinth inside the case and two vertical in-line ribbons which enabled it to be uni-directional.
References
External links
RCA Type 77-A information from www.coutant.org
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Ribbon microphones