This circuit, to add the ambience effect, was suggested by National Semiconductor in documentation from the 90s. The amplifier needs an appropriate power source.
This circuit for frequencies of 20 to 2 kHz was obtained in English documentation from 1966. The...
The oscillator of this circuit operates around 8 MHz, but the output will be at a frequency three times...
This circuit with transistors of the time was found in the magazine Radio Electroinics of June of...