This circuit, with printed circuit board, is from an article in Radio Electronics magazine from May 1971. The circuit uses the C106 which was already a common component at the time.
This circuit was found in a 1967 Electronic Design. FETs are from the time, so modern equivalents can be...
This circuit was found in 1968 General Electric documentation. The circuit uses components from the era...
This circuit acts as a VU-meter when connected at the output of any audio amplifier, triggering a...