This simple 1-transistor audio preamplifier appeared in the June 1968 Radio Electronics magazine. The transistor is a general-purpose type of the time. The gain is 14 dB.
It can be obtained from Mouser Electronics new superFETs III from Fairchild for voltages of 700 V...
This circuit was found in a 1969s American documentation. With modern components, it can be used...
The figure shows how to change the frequency of a 5 V LED blinking. The capacitor can have other...