A 3.5mm headphone amplifier will boost the sound signal coming from your Tablet and eReader headphone jack, so you can hear it louder from your headphones.It does this by using electricity from the headphone amplifier to boost the electrical current for powering your headphone to reproduce sound.
An Example of a Headphone Amplifier is the Fiio E3 Headphone Amp which is powered by a single AAA battery with a battery life of 20 hours. It can increase the sound's volume for high impendence and low sensitivity headphones which are low without an amp. Amps for headphones will also increase your battery powered music players battery life because it means you can lower the volume on your music player or tablet eReader, and still be able to enjoy louder music at a lower volume because it is amplified with a headphone amplifier. It can also improve the bass and treble for your headphones to have a better listening experience. It only costs 7.50 US dollars on Amazon, but can make your Tablet, eReader, MP3 player, Netbook, Laptop, and other device with a 3.5mm headphone jack sound like a more expensive louder player.