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 found in a 90s Hands-on Electronics. The transistor can be a BC548. What it does...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
Based on an LM36000 OTA this circuit was found in the July 1988 issue of Radio Electronics...