The rack mount power amplifier is assembled with all the elements in a 2U chassis offering 350/450/650 watts,

available with either 70/100-volt or 4 to 16 ohms(Ω) loads.

The front stage is mainly used to provide appropriate audio electrical level signals for the post stage and adjust the sound quality such as the high and low bass effect, the left and right channel volume and so on. The post stage, commonly known as pure post stage, it simply amplifies the  audio signals provided by the front stage to provide enough power to drive the commercial pa speakers.