Found in a 90s Popular Electronics, this mixer can be expanded to more channels. Transistors can be modern general-purpose equivalents.
This circuit with power MOSFETs was found in a 1980s Siliconix documentation. Equivalent MOSFETs...
This 80's General Electric circuit is guarded by the noise-guard for operating current. The...
This circuit was obtained in a 1964 Electronic Design. The components used are from that time....