When you listen to the same note on your Hi Fi at home the loudspeaker is vibrating to make the sound wave. Usually the sound wave from the Hi Fi is not quite the same as the one made by the original instrument. We say that it has been distorted . So it won't sound the same as the original instrument, although it usually sounds pretty similar. The more that the wave has been distorted, the less the Hi Fl will sound like the original.
Distortion is the enemy of the perfect audio system.
There are many ways that a sound wave can be distorted. To avoid distortion, each stage should have no noise , a flat frequency response and linear gain . Find out on the next page.