Accu Box S2 USB is an accu driven power supply that delivers perfectly transmissioned power to any 5V input product. The big advantage being that the power supply is then separated from the polluted mains. No disturbing interference can be passed on to the unit this way, resulting in a more clear and spacious sound signature. The 2600 mAh capacity will give many hours of listening pleasure. In contrary to regular power banks, Accu Box S2 USB uses Li-Ion batteries. The LEDs on the front panel indicate when the unit needs to be connected to its power supply and if it is powering a separate unit. The superior aluminium/metal casing not only looks great it also protects effectively against vibrations and electromagnetic interferences!