IRF Mosfets are known for its use in HF amplifiers up to about 20 MHz. These Mosfets can also be used for LF applications. Greg Szekeres has designed a straight forward headphone amplifier that operates in class-A mode. Therefore, good audio quality is garanteed.
Using only 12 components you can build your own 1-channel headphone amp. You can use it to connect it to the audio output of your CD- or MP3- player. Also it can be used as a final stage in your receiver designs.
An N-channel Mosfet IRF513 is used. Similar types as IRF510 or IRF520 can be used instead. Two diodes are present as means for protection. In principle this circuit has been designed to be used with 30 ohms headphones. Greg informs that the quality of C2 is important for the overall quality of this amplifier. Since this amplifier operates in class-A about 2.5 Watts electrical power is dissipated even when no audio is presented to the input of this amplifier.
In case the audio output appears to be too low, a 1-transistor input pre-amp stage should
More DIY headphone amplifier designs:
My version of the 1-channel headphone amplifier on VERO board