This circuit of the 70's uses transistors of the time. The circuit can amplify signals from 10 Hz to 100 kHz and modern equivalent components can be used. The circuit is from Ferranti.
This amplifier with complementary symmetry output and good sound quality was found in...
This circuit should be placed between the signal source and the input of a recorder or amplifier....
Found in an Electronics World of 1968 this circuit can use current SCRs and the diodes are...