What is the difference between a pre-amplifier and a power amplifier?

toc Bass amplifiers, whether they are combo amps or stage rigs, contain three components: the preamplifer, power amplifier, and the speakers. The signal from your bass passes to the speakers in three stages, with an amplifier between each of the stages. The signal from your bass is carried at instrument level; floor pedals, which your bass plugs into directly, operate on the signal at this level. The instrument level signal is amplified to line level by the preamp. The line level signal is passed to rackmounted effects. Because the line level signal is more powerful than the instrument level one, rackmounts effects add less noise relative to the level of the signal than floor effects do, which is why professionals prefer them. Most preamps sold commercially also include a number of line level effects, though not all do. After the line level signal is processed it is passed to one or more power amplifiers. Most rigs use only one power amp but if you are biamping you would use two. The ...  more