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 for frequencies from 1Hz to 100 kHz was found in the June 972 Radio Electronics...
This circuit generates short pulses. The transistor can be a 2N2222 or BC548 and the frequency is given by...
We found this filter in a Popular Electronics from 1993. The operational amplifier can be the 741....