The

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

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 electromag ...

, the forerunner of the

RCA Type 77-DX microphone The RCA Type 77-DX microphone is a poly-directional ribbon microphone, or pressure-gradient microphone, introduced by the RCA Corporation in 1954. It was preceded by the Type 77-D introduced in 1948. Its popularity and classic design has resulted ...

. 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.

External links

RCA Type 77-A information from www.coutant.org
{{product-stub Ribbon microphones