This circuit was found in documentation from the 1980s. The circuit uses several components of the time, which are uncommon today. We must not supply it with a transformerless power supply.
This is 4-input audio mixer using an integrated circuit 741 and two more operational amplifiers....
The CMOS 4060 integrated circuit consists of a frequency divider counter with internal elements...
Found in 90s Popular Electronics, this circuit fires a load through a MOSFET from an audio signal...