This two-transistor circuit is from a December 1964 Radio Electronics. Modern transistors can be tested. The headphone must be high impedance or crystal with a 2k2 resistor in parallel.
This circuit for controlling high power in the AC network was found in a Motorola documentation from 1968....
This amplifier is specifically designed for portable radio and recorders with a 4 ohms load....
This circuit was found in a 1973 Radio Elettronica magazine. The Italian magazine no longer...