DIY Class A Headphone Amplifier

The computer sound card just didn't cut it when it came to driving my 32 ohm Grado SR80 headphones, so the need arose for a decent desktop headphone amplifier. Lately I have been reading a lot about Class A amplifiers and have been eager to try one, so a small and simple Class A headamp seemed like a logical first step in this direction.


The circuit is a simple single-ended amplifier with an active load. An inexpensive IRF610 MOSFET is used as the output device and a LM317 voltage regulator is configured as a constant current source (CCS). The power supply is a regulated wall wart which works very well and there is no hum. For the enclosure I used a dead external CD-ROM. This worked out very well as it will reside on my desk at work. I'm sure everyone will be wondering why I have an old external CD-ROM hooked up to a new laptop!


The results were very good. Despite the simplicity of the amplifier circuit it sounds surprisingly good. For more details, photos and a schematic, see the DIY IRF610 MOSFET Class A Headphone Amplifier Project page.

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