This old 1 W audio amplifier transistor circuit is from a 1967 Japanese magazine. The transistors are germanium of the time and the type transformers found in similar equipment of the time.
Using an operational amplifier, the figure shows how to convert the waveform to low frequency...
This high quality circuit with complementary symmetry was found in an Electronics World of 1966....
This circuit was obtained in an old 1983 magazine, but it can still be easily assembled. The...