This 4-channel mixer amplifier was found in an American publication from 1947. The circuit uses counterphase output tubes and a transformer power source.
This circuit is from a 1978 French magazine Electronique Pratique. The magazine no longer exists, but...
The difference in this circuit, found in documentation from the 90s, is the use of a single...
We find this simple tone modulated signal generator in a 1987 publication. It uses common...