RCA 4-A-1 Condenser Microphone

RCA Condenser Microphone

This is the model 4-A-1 microphone made by RCA Victor in the early 1930's.  This design represented the state of the art at the time and was a workhorse in the broadcast industry until it was supplanted by the model 44, and later the 77 ribbon velocity types.  For obvious reasons, it is commonly called the RCA "box camera".

RCA Condenser Microphone Nameplate

RCA Condenser Microphone-Front View

Because of the very low output of the condenser type microphone element, a three tube amplifier was incorporated into the housing.  The added size and weight of this amplifier, the heavy multi-conductor cable, and the associated power supply made this unit practical only for studio use.  The unit shown here has the original NBC plate on the back side (which would have faced a live audience).  The tubes inside also bear NBC markings.  The amplifier was cradled in a blanket of foam rubber which is now much deteriorated with age.  Shown below is a spare element for this microphone, with its original packing container.

RCA Condenser Microphone Amplifier

RCA UZ-4083-B Microphone Element

RCA UZ-4083-B Microphone Element Container