Yamaha NX-U10 - Manual (Page 3)

If music varies in loudness or includes rests, its signal level is not constant.
The power used to play music is an average of about 1/8 of the amount
that is supplied. The remaining 7/8 of the power is unused. The
PowerStorage Circuit
stores this unused
electric power and
supplies only enough to
match the music level.
This high efficiency
PowerStorage circuit
can achieve 20W
output even with the
small quantity of power
supplied via USB.
How does it work?
PowerStorage™ Circuit
Peak Required Power
Unused Power
= Stored Power
Max. Instantaneous Power: 20W
Maximum Power
Supplied by USB (2.5W)
Music Level
time PowerStorage™ Circuit Conventional USB Speaker
Handy and versatile
Connecting the NX-U10 to your laptop or other computer is
quick and easy. You only use one USB cable — no need
for a power cord. Or you can power it from an AC outlet
or four AAA batteries. It also has a stereo mini jack, so you
can plug in your iPod, game console or other portable
device to enjoy bigger, better sound.
NX-U10 | USB Powered Stereo Speaker