A series class-D power amplifiers have three ranges one channel, two channel and four channels, each channel, s rated power have options of 120W, 240W, 350W and 500W. 19-inch, Standard rack mount design in 2U height. VA series class-D power amplifiers are designed of switch power technology for power electricity saving, separate PFC design for highest reliability, separate power supply system for each channel, separate cooling system for each channel ensure less heat generation and fast auto-cooling system. Sleep mode is automatically enabled when no signal input is detected. AC 110V or 230V power supply and 24Vdc input, separate fuse for each channel. Balanced line input by phoenix connector and 100V line speaker output by phoenix connector. Built-in two fans for automatic start up when inner temperature reaches 55°C. Complete protection system includes power on, overheat, short circuit and overload.