This circuit with RIAA equalization is from 1985 US documentation. The circuit has a flat response of 150 Hz to 40 kHz. The power supply must be symmetrical.
This headphone amplifier has good gain and high input impedance. The circuit is from Electronics Now and...
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
Incandescent lamps and heaters can be controlled by a low power switch using this circuit. The...