FiiO E11K Kilimanjaro 2 portable headphone amplifier with Bass, Gain and Alps potentiometer for smartphones, music players and computers (electronic) 4
Tested on different iOS devices with B & W P5, and RHA 750i. In quieter volume level said KH models both from the performance boost of Kilimanjaro 2. benefit "out from below" is just more pressure available :-). In my opinion, the P5 benefited clearly from Kili2 than the RHA. Device does what it should. Charged it to the USB port. A separate battery charger is (unfortunately) not available. However, the price / performance ratio is good!