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-DX microphone is a poly-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 ...

, 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 in the 77-DX becoming an iconic microphone, used by broadcasters and media personalities such as

Edward R. Murrow Edward Roscoe Murrow (born Egbert Roscoe Murrow; April 25, 1908 – April 27, 1965) was an American broadcast journalist and war correspondent. He first gained prominence during World War II with a series of live radio broadcasts from Europe f ...

, David Letterman and

Larry King Larry King (born Lawrence Harvey Zeiger; November 19, 1933 – January 23, 2021) was an American television and radio host, whose awards included 2 Peabodys, an Emmy and 10 Cable ACE Awards. Over his career, he hosted over 50,000 interviews. ...

Controls

The directionality of the 77-DX is variable. A rotating backshutter on the acoustic labyrinth, controlled by a screwdriver-operated slot at the rear of the microphone, allows the user to vary the microphone's pattern from omnidirectional in the fully closed position, to cardioid, to figure-8 (bidirectional) in the fully open position. A 3-position switch at the bottom end of the microphone allows the user to control the amount of low-frequency rolloff.

Response and output characteristics

At 1 kHz, the 77-DX has an output of -50 to -56dbm, depending on the pattern selection. The output impedance is user-selectable; factory preset at 250 ohms, and changeable to 30 or 150 ohms. The microphone has a fairly flat response. In the cardioid (unidirectional) pattern, it is level from approximately 150 Hz to 2 kHz, with a slight rise peaking at just under 5 kHz, then dropping approximately 3 dB/octave to 20 kHz.

User techniques

The 77-DX has been used on countless vocal recordings by Bing Crosby, Kate Smith, Frank Sinatra,

Elvis Presley Elvis Aaron Presley (January 8, 1935 – August 16, 1977), or simply Elvis, was an American singer and actor. Dubbed the "Honorific nicknames in popular music, King of Rock and Roll", he is regarded as Cultural impact of Elvis Presley, one ...

, Johnny Cash, Al Green, and many others. It is still sought after today for use in recording brass instruments. Audio engineers experienced with the 77-DX can position the microphone at different angles to modify its frequency response. For example, with the microphone suspended, tilting it on the horizontal axis will cause the ribbon to sag slightly, resulting in a noticeable boost in the lower-midrange frequencies. The ribbon is positioned inside the housing in such a way that "p" sounds (

plosives In phonetics, a plosive, also known as an occlusive or simply a stop, is a pulmonic consonant in which the vocal tract is blocked so that all airflow ceases. The occlusion may be made with the tongue tip or blade (, ), tongue body (, ), lips ...

) may cause popping sounds, due to the explosion of air directly into the ribbon. A common solution to this problem has been to attach a

pencil A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage, and keeps it from marking the user's hand. Pencils create marks by physical abrasion, leaving a trail ...

vertically across the front of the microphone. The pencil deflects a vocalist's breath as it reaches the microphone, and prevents it from hitting the ribbon directly.

References

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External links

RCA Type 77-DX microphone information from www.coutant.org
Microphones

Controls

Response and output characteristics

User techniques

See also

References

External links