Eighty-five years ago, this young woman was preparing to have her voice amplified with this 30-watt amplifier. We don’t know whether she’s a ham modulating her transmitter to almost 100% modulation, or if she is going to address a crowd through the loudspeaker. The circuit shown here, from the May 1938 issue of Radio News, is suitable for either purpose.

The power output was provided by two 6L6 tubes, and the circuit’s main feature was automatic volume limiting, which would provide distortion-free audio, even at maximum power. This was important for modulating, since the FCC required that modulation be limited to 100%. And for PA work, this meant that the output would be not only loud, but also crystal clear.