Found in an Electronics Now from the 90s this mixer has several inputs. The integrated circuit can still be found easy and the power supply need not be symmetrical.
White noise applied to an audio amplifier can be used as a relaxant, since it resembles the noise...
This circuit fires a xenon lamp being powered by a 300 V battery. The circuit is from a Radio...
The operational amplifier of this circuit is not very common today, because we removed the circuit...