pre amplifier voltage clipping
The amplifier is going into cutoff saturation with the higher input signal. Also, the input biasing is off by a bit so the clipping is asymmetrical.

Actions: 


Reduce the gain of the amplifier to keep the output within the linear part of its curve.
Change the DC biasing of the input signal to center it on the midpoint of the linear part of the output curve. 


To do this empirically, use a potentiometer instead of one of the two fixed resistors, to figure out what resistor ratio puts the null point closes to the middle of the output linear curve portion.

Thanks to @ThePhoton for pointing out my incorrect use of "saturation".