a voice that needed no amplification不需要使用扩音设备的大嗓门

that amplification of the elements in his character that made him able to dominate her他性格中使他得以支配她的那些因素的强化

The point is made rather sketchily and would benefit from some amplification.对这一点的说明过于简略, 扩充一下会更好。