The Pico Power is one of the best all-round portable amps available, able to drive everything from IEMs to full-sized headphones well.
Pros: Jewellery-quality build, smallest dual-9V portable amp, wide range of gain settings, controls well thought-out, beautiful case.
Cons: Not enough power for orthos. Batteries must be removed to be charged. Battery fit is very tight.
One of the well-known disadvantages of portable amps has always been, simply put, a lack of power available, being that they are limited to using batteries. While with in-ear monitors and more easy-to-drive headphones this isn't such a problem, it limits their capabilities when it comes to either high-impedance headphones (which sound best with amps that can consistently swing a greater voltage) and headphones such as lower-sensitivity orthodynamics (which sound best with amps that can deliver high amounts of current). While it is readily possible to cram a larger battery and more capacitors (to hold more reserve power for peaks in the music) in a case, the result quickly becomes ungainly in size.
Audioquest Dragonfly (with power from an Aurorasound USB Bus Power Pro), Pico Power and Symphones Magnums (Grados with custom drivers).
February 2014: More pictures: