Found in a 1967 Electronics World, this preamplifier uses an integrated circuit from that time, difficult to obtain today. The maximum frequency is 15 kHz.
Only one LED is turned on when S1 and S2 are pressed. The LED that will be on is just the...
This circuit is based on one of the first germanium transistors. The power comes from a solar cell...
This circuit was found in an American 80's circuit board. The components used are current except the...