How Do Guitar Amps Work?
A guitar amplifier works in a three stage process to amplify the signal delivered from your pickups and through your cables. Your music passes through a preamplifier before being sent to the power amplifier. Some amplifiers also have a tone stage to modify the signal before amplifying it. There are different amplifier arrangements that achieve each stage through a separate piece of equipment or smaller combination amplifiers that combine all stages into one unit.
As it’s name implies the power amplifier does the bulk of the work of amplifying your sounds, powering up your music. However, the signal coming directly from your instrument does not have sufficient voltage for the power amplifier to use it. This is where the preamplifier comes in. Before the music you want to amplify reaches the power amplifier, the preamplifier amplifies the voltage of the signal coming from your guitar. In short, first the preamp amplifies the voltage of the signal then the power amp amplifies the signal itself.
The tone stage can come before or after the preamplifier stage. Pedals and other signal altering tools come before the preamplifier stage. As mentioned above some amplifiers have built in tone effects to change your sound such as distortion, chorus and reverb. These are usually included after the preamplifier stage but before the power amplifier.
There are many different ways to arrange the phases of amplification from effects pedals and boards to amplifier cabinets and mixers but they all follow the same general three stage format.