You can overdrive and overload an amplifier.
If you apply 2V to an amp that is designed for 1V, you will overdrive the amp. The amp might be designed to accept up to 1V and amplify that signal linearly by say, 50 times. With 1V applied, the output at your speaker could therefore be as high as 50V. Beyond 1V, the output is amplified linearly by a factor of 50 and there are non-linear components as well that result in harmonic distortion. These non-linear components are added to the linear component and you get distortion that sounds like crap. This is called clipping because when you compare the output signal to the input signal, it looks like someone has cut the top of the output signal off.
An overload is different. If you apply a voltage that is above the insulation level of the circuit, you could get fireworks.
