The AudioQuest DragonFly has been a phenomenon. It was one of the first portable USB headphone amps, and has built a reputation for also being one of the best.

You could easily mistake it for a USB key, and it even comes with a dust cover for the USB plug end that serves to enhance that impression. The only giveaway that it's packing some sonic smarts is the discreet 3.5mm jack socket - there are no volume controls on the DragonFly, so you have to alter levels via your computer.

It does feel quite solid, despite its size, and things get a little more fancy when it's plugged in - a dragonfly-shaped multicolour LED lights up to display the device's status.

The AudioQuest really makes its biggest statement when you plug some headphones in and start listening, though. It has a cohesive, well-rounded sound with good warmth but a perfect definition to percussion. The DragonFly also has beautiful timbre with strings - through our reference Grado GS1000e headphones, the plucking in the opening of Andrew Bird's The Giant of Illinois sent a shiver down the spine.

In fact, the AudioQuest DragonFly handles every type of music with aplomb. That reputation is well deserved.