RCA Type 77-A Microphone
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The RCA Type 77-A microphone was a uni-directional ribbon microphone and was the forerunner of the RCA Type 77-DX microphone. Dr. Harry F. Olson designed the 77-A sometime during the late 20's or early 30's, prototypes are rumored to have existed in 1929 and 1930 but, the 77-A wasn’t announced until 1932.
The 77-A would set the standard for all other RCA ribbon microphone comparisons for the next 40 years.
[edit] Construction
It featured an acoustic labyrinth inside the case and two vertical in-line ribbons which enabled it to be uni-directional.
