Compact size class D Audio Powered Amplifier with on-board power supply. The size of the amplifier is 150mm long, 56mm wide and 36mm tall including the bottom spacers and Power IC height. With a weight of the board alone of only 240 grams, it can reach a power density of 1.5W/gram and an overall volume of just 20 cub. inch has a power density of 18W/cu.inch, being the most compact powered amplifier in it’s class, available on the market. Output power is 2x170W on 4 Ohms load impedance or 2x90W on 8R load impedance. The output power in BTL mode is 340W on 8R speaker impedance. All these power ratings are measured with <1% THD. The supply voltage is either 115V AC, or 230V AC, 50 or 60Hz. Signal input can be balanced or unbalanced, and can be chosen while wiring the input signal. It has the Mute function and LED visual indication for the amplifier status. The amplifier features over-voltage, over-current and short-circuit protections. The amplifier gain is 30dB in Single-ended mode and 36dB in BTL mode. For proper operation the board must be installed on a heatsink or an aluminium baseplate which will serve as heatsink. Note that the power IC is mounted on the backside of the board allowing easier installation. The power transistors and rectifier diodes from the power supply section do not require heatsink for operation with music signal due to the high efficiency of the power supply. The overall efficiency from mains supply to speaker is over 87.5% measured with 230V mains voltage supply and 360W at 8R output power in BTL mode with 1% THD.