This is an 1-watt amplifier especially designed for use as a driver for a low impedance headphone. The circuit uses the TL081 op-amp and a push-pull transistor output stage.
Feedback resistors R3 and R4 fix the gain at about 15 dB. The overall distortion from 10 Hz to 30 kHz is less than 0.1%.
The amplifier delivers a maximum power of 1 watt into 8 OHM for an input signal of about 500 mV rms. High-impedance headphones may also be connected without any problem.
The two transistors should be mounted on heat sinks and you must use insulating washers and heat conducting paste.
You may build a simple power supply unit to power up the headphone amplifier. The supply unit may consisting of a mains transformer, having a centre-tapped - 0.5A secondary of 6 to 8 V, a suitable bridge rectifier, and two 1000 μF/35 V electrolytic capacitors in a conventional arrangement.
The headphone amplifier circuit can be used for a single audio channel. Therefore, if you want to create a stereo version of the amplifier, you may use two identical circuits.
