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RCA MI 6203 VARACOUSTIC- The 'Gas Pedal'



With the MI 6203, RCA developed a new idea in ribbon microphone design. Their previous models were bi-directional and pricey, intended for the professional broadcast market.

To create a directional model, Harry Olson, RCA's legendary inventor, combined two ribbons in the 77A model to create a directional pattern. The price of the 77A was enormous, as was the casing, a grenade-like canister. Olson reduced the microphone size in the later models 77 B and 77 C, in which he used one ribbon as two separate parts, those models were also pricey and fragile.

With the Varacoustic, he introduced a ribbon microphone that could function directional, bidirectional and omnidirectional. The different settings could be made with a slider on the back.

The MI6203 was intended for PA use, in public address systems and for amateur radio stations. It also became popular with artists, at a time when there were few directional microphones.

The same motor (ribbon and magnet) was used for the later iconic 77 D, but the shutter and acoustic chamber are different. Overall, the 77D sounds better and the Varacoustic housing further degrades the sound.

Varacoustics were made from 1945 to 1949, in two versions: the high-impedance variant was called MI 6204. The later SK 50, with a similar appearance, was made from ca. 1950 to 1960. The version shown here, with a slightly different housing, was made by RCA England. This housing is better designed than the American original, where the two parts often parted from each other, in the British version this is prevented by the extra screws at the top.

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

wow cover

RCA MI6203 Varacoustic

RCA Varacoustic ad

RCA MI6203 back

Top: RCA Varacoustic, UK version

Middle: ad from the forties and back side of the mic

Below: sound and Orson Welles in front of a MI 6203

Listen to the sound of the RCA Varacoustic

Orson Welles with RCA MI6203 Varacoustic