This circuit, found in a 1958 magazine, is for reference only, since the components are not easy to find today. The transistors are germanium types and power supply is made by common cells.
This is a typical common collector amplifier step configuration. The transistor can be used...
September 2017 - Texas Instruments PCM186x and PCM186x-Q1 Audio ADCs can be found at Mouser...
We found this traditional configuration of a megaphone with a coal microphone in an American...