RCA Type 77-DX microphone
Encyclopedia
Type and manufacturer
The RCARCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
Type 77-DX microphone is a poly-directional ribbon microphone
Ribbon microphone
A ribbon microphone is a type of dynamic microphone that uses a thin aluminum, duraluminum or nanofilm ribbon placed between the poles of a magnet to generate voltages by electromagnetic induction...
, or pressure-gradient microphone, made by the RCA Corporation from 1954 until 1960, replacing its predecessor, the Type 77-D. Its design has inspired a stereotypical microphone icon. Throughout the 1950's and 1960's, phonograph record album cover
Album cover
An album cover is the front of the packaging of a commercially released audio recording product, or album. The term can refer to either the printed cardboard covers typically used to package sets of 10" and 12" 78 rpm records, single and sets of 12" LPs, sets of 45 rpm records , or the front-facing...
photos show artists singing into the side of a 77-DX.
Controls
The directionality of the 77-DX is variable. A rotating backshutter on the acoustic labrynth, 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 desired amount of low-frequency rolloff.
Response and output characteristics
At 1kHz, the 77DX 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 150Hz to 2kHz, with a slight rise peaking at just under 5kHz, then dropping approximately 3dB/octave to 20kHz.User techniques
The 77-DX has been used on countless vocal recordings by Bing CrosbyBing Crosby
Harry Lillis "Bing" Crosby was an American singer and actor. Crosby's trademark bass-baritone voice made him one of the best-selling recording artists of the 20th century, with over half a billion records in circulation....
, Kate Smith
Kate Smith
Kathryn Elizabeth "Kate" Smith was an American Popular singer, best known for her rendition of Irving Berlin's "God Bless America". Smith had a radio, television, and recording career spanning five decades, which reached its pinnacle in the 1940s.Smith was born in Greenville, Virginia...
, Frank Sinatra
Frank Sinatra
Francis Albert "Frank" Sinatra was an American singer and actor.Beginning his musical career in the swing era with Harry James and Tommy Dorsey, Sinatra became an unprecedentedly successful solo artist in the early to mid-1940s, after being signed to Columbia Records in 1943. Being the idol of the...
, Elvis Presley
Elvis Presley
Elvis Aaron Presley was one of the most popular American singers of the 20th century. A cultural icon, he is widely known by the single name Elvis. He is often referred to as the "King of Rock and Roll" or simply "the King"....
, Johnny Cash
Johnny Cash
John R. "Johnny" Cash was an American singer-songwriter, actor, and author, who has been called one of the most influential musicians of the 20th century...
and many others. It is still sought after today for use in recording low brass
Brass instrument
A brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips...
.
The foil ribbon element in a 77-DX will respond to gravitational force as the microphone is positioned or tilted. Audio engineers experienced with the 77-DX typically suspend, hang or position the microphone at various angles to achieve a variety of desired frequency response characteristics. For example, with the microphone suspended, a slight tilt 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 fricatives
Fricative consonant
Fricatives are consonants produced by forcing air through a narrow channel made by placing two articulators close together. These may be the lower lip against the upper teeth, in the case of ; the back of the tongue against the soft palate, in the case of German , the final consonant of Bach; or...
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
Pencil
A pencil is a writing implement or art medium usually constructed of a narrow, solid pigment core inside a protective casing. The case prevents the core from breaking, and also from marking the user’s hand during use....
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.