This 8 W amplifier with germanium transistors was found in a Japanese documentation from 1967. The circuit is of the commercial type and is powered by two 12 V batteries or by a symmetrical source.
This circuit is from 1977 documentation, but can be assembled with BC548 for Q1, Q2 and Q4, BC558...
Found in American documentation from the 90s, this circuit uses components that are still common...
This high impedance input amplifier is suitable for the use with piezoelectric sources such as...