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RCA 88-A / MI 4048A



The 88-A (MI 4048A), from 1938, was RCA's first true dynamic microphone. Although the company had already released a 'dynamic', in 1933: the Type 50, similar in shape to Western Electric's 618 'searchlight'.

RCA's 'inductor' microphone was however different in it's operation principle: a thin aluminum strip, coupled to a stiff diaphragm, moved between two magnetic poles. It was a hybrid design with similarities to both ribbon and moving coil dynamic microphones.

RCA probably wanted to circumvent the patent rights from Western Electric's dynamic microphone design. Later, RCA used this same inductor principle for their KN 1B model (a simple mic, for paging and PA use).

The 88-A was the first RCA that worked according to the usual dynamic principle. It was a very robust design, with Art-Deco and 'Space-Age' influences. It had a strong output and a great beefy sound.

The model was part of the company's Broadcast portfolio, together with the well-known ribbon microphones, and was meant for remote pick up use: close talking under less than ideal circumstances, situations where studio mics might pick up too much background noise.

The microphone could be used horizontally (semi-directional mode), or vertical (omni mode) and was practically insensitive to wind and moisture.

Due to its small size and light weight, it could easily be held in hand by reporters. Combined with the new tape recorder, it became a mobile recording unit, which offered journalists the possibility to work outside the studio, on site.

The end of WW2 did not bring only Coca Cola to Europe; RCA 88's were used for the processes of Nuremberg, in 1945-46; the Nazi war criminals spoke their confessions, or denials, in these microphones.

The 88 A was so successful that fourteen years elapsed, before RCA decided to finally replace this model with a more modern type: the BK 1 (mic of the month May 2016).

Because of their great quality, many of these microphones still function perfectly.

These and many more types feature in my book Witnesses of Words. More information about that can be found at

wow cover

RCA 88-A
RCA spec sheet

Top: RCA 88-A & spec. sheet

Middle: Sound & RCA 88-A ad, 1939

Bottom: Nazi's at the Neuremberg tribunal

The sound of the RCA 88-A

RCA 1939 ad
88-A_War criminals