Does one need a separate mp3-player amplifier?
Your mp3-player has a built-in amplifier which is strong enough to boost your IEM to an enormous volume. In other words, you don’t need an extra amplifier to pump up the volume. A portable amplifier could be of use if you want to connect your head phones to your mp3-player, while these head phones have too high impedance (resistance expressed in Ohm). Because of the higher resistance the internal amplifier of your head phones might not be able to feed your head phones sufficiently, and therefore, the sound might be distorted.
Most IEM have low impedance. An external amplifier makes sure that the complete range of frequencies is amplified proportionally. The (weaker) internal amplifier is not strong enough to do that.
How to connect the external amp
A portable amplifier has the strongest effect if it passes by the internal amplifier. Some mp3-players have a separate line out or optical output. By using a DAC (Digital to Analog Converter) you can connect your portable amplifier to it to make sure that all frequencies are amplified proportionally. This yields a clear and dynamic sound.
Older portable CD-players, like Sony’s, have a much better internal amplifier. In those times there was more room inside the gear for a powerful build in amplifier. More modern mp3-players are made as small as possible which you can tell by the quality of the amplifier. Most people won’t be aware of this, because you can’t tell the difference with standard ear plugs. The size of the player is more important to them than the sound quality.
Better sound quality with an mp3-player amplifier?
Opinions differ. Some people swear to an external amplifier and hear a significant difference in quality. Others think that a portable amplifier doesn’t add much to the quality of sound of their IEM. For them the internal amplifier is strong enough because of the lower impedance of the IEM. Provided that the mp3-player has a fairly good internal amplifier. The last generation iPods and the iAudio mp3-players suffice amply.
So, it’s up to you to decide whether you’ll need an external amplifier. You should realize that you’ll have to carry this external gear with you and that your mp3-player must be equipped for it. Besides that, an amplifier of reasonable quality will cost you $ 100 or more.
