The Legacy of the RCA KU3A
The KU4 celebrates the legendary RCA unidirectional KU3A, a high- sensitivity microphone designed for the Hollywood movie studios. Also known as a M-10001 for its manufacturing number, it was RCA’s most expensive ribbon microphone. Fewer than 600 were ever manufactured.

What made the KU3A special?
It combined the smooth ribbon sound of a 44 with a unidirectional pattern, a wide sweet spot and less proximity bass boost. It expanded an engineer’s range of placement choices and became a standard at film studios around the world.

Although condenser mics became the new standard by the end of the 1960s, ribbon mics are still appreciated today by experienced music recording engineers. However the KU3A is a rare microphone, a collector’s item, and few studios or rental houses own them. Opportunities to work with a good KU3A are limited.
We are proud to expand your opportunities with the AEA KU4 featuring an RCA ribbon, interchangeable KU3A parts and consistent performance.

How is the KU4 different from other ribbon microphones?
The KU4’s supressed rear lobe is useful when the back of a figure-of-eight would pick up undesirable sounds. The KU4’s reduced proximity bass boost facilitates closer micing and its low-tuned ribbon delivers solid, undistorted bass. These characteristics make the KU4 well suited for modern studio production.
Its lightly-tensioned, ultra low mass ribbon has a frequency response out to 40 kHz and fast, accurate transients. There is no upper midrange ringing common to large condenser mics. The KU4’s ribbon is well protected and its field-tech replaceable pole piece and ribbon assembly is a real convenience if an accident occurs.

The KU4 is your ticket to discovering why the KU3A has been part of high-end studio life for over 60 years. AEA is honored to play a part in its history, and invites you to listen to the KU4 and claim your part of this legacy.