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 was adapted from an Italian publication that no longer exists. This is “Onda Quadra”...
This circuit was obtained in an Electronic Engineering of the 90s. The operational amplifiers and...
The basic component of this circuit is a general-purpose SCR. The voltage is according to the...