Found in a February 1949 Radio Electronics magazine, this dual tube mixer has 4 inputs. Power must come from a 250V source.
We found this high gain circuit with the LM381 preamplifier in a Radio Electronics from February 1990....
This circuit provides a good audio power from a signal at least 1 V of amplitude. The MOSFET must...
Using a CA3130, operational amplifier with FET, we found this circuit in a 1977 publication. The...