Seventy years ago, the transistor was still the new kid on the block, and designers had to work around its limitations. It was hard to get it to work as a radio detector stage, so this design, from the September 1955 issue of Radio-Electronics dealt with the problem by using a hybrid circuit. A subminiature CK7088 pentode was used for the regenerative detector, and a transistor was used to amplify the audio. The circuit called for a Texas Instruments type 200, but the venerable  CK722 could be used with some modifications to the circuit.