A headphone amplifier is simply a miniature power amplifier specifically designed to drive the tiny speakers inside headphones.
Headphone amps are most useful with certain power-hungry high-impedance audiophile headphones that can benefit from the improved clean power of a dedicated amp. A headphone amp can improve detail resolution and dynamic range extension and maximize overall musical clarity.
Because headphones are often used with portable devices, some headphone amps are battery-powered for use on the go.
Some headphone amps also include built-in digital to analog converters (DACs) with a USB or optical port to connect directly with a laptop, PC or tablet, as well as optical and coaxial connections for compatibility with other digital audio sources.
A good headphone is like a good speaker, and needs a power amplifier to sound its best.
While nearly all headphones can be improved with amplification, some headphones require an amp to sound their best.
A DAC (Digital to Analog Converter) will turn your computer (or other digital-output device) into beautiful music.