Definitions for "Power amplifier"
A power amplifier takes the low-voltage signal supplied by a preamplifier, and increases it to a sufficient level to drive speakers. Receivers contain both preamplfier and power amplifier sections, eliminating the need for a separate amp and preamp.
An amplifier that takes line level audio signals and make them strong enough to power a speaker.
The power amplifier takes the low-voltage signal supplied by the soundcard and amplifies it to a sufficient level to drive speakers.
Keywords:  alone, stand, separate, different, unit
a separate, stand-alone unit because of its different RF requirements