Amplifiers
A home stereo amplifier collects an audio signal from your media source then boosts the signal’s gain before sending it to your speakers. The speaker wire that transmits the audio signal also carries enough electricity to power the speaker. That’s why the most stereo speakers don’t require a power cord. Audio receivers and home theater receivers feature a built-in amplifier (and preamp), allowing them to perform the same basic function. But receivers also include a built-in radio tuner,so that they can play music without pulling it from an external device.
So, receivers are all amplifiers, but amplifiers are not receivers because they lack a tuner.
Integrated amplifiers combine the functionality of a power amp and a preamp. Preamplifiers work to boost the audio signal from analog sources before it reaches the power amp. In a home audio environment, a turntable is one of the few devices that requires a preamp. Other analog audio sources include microphones and musical instruments. But those of us who aren’t recording music will probably only need a preamp for our turntables. Regardless of the source of your audio, systems with separate stereo amps and preamps provide higher sound quality.
The Different Types of amplifier: