The most obvious way of selecting pre- and power amplification that works together well is by sticking within one brands range. Invariably they will have been tuned to work well together. Car Power Amplifier Circuit Using C5100 A1908 Car Amplifier Amplifier Car Subwoofer Simply put no tech-speak it is the job of an amplifier to make sound louder. . So if youre running a 100 wattch AV Receiver and upgrade to a 500 wattch external amp then you simply plug into the formula as follows. Since the impedance of the loudspeaker is still 8 ohms we have to apply double the voltage ie. 7242 Higher amplifier output power. The input is where the source of the sound is attached or fed to the amplifier. Its also why most professional power amplifiers use 12 Vrms or a close value as their input sensitivity as it will drive the amplifier to its full output voltage. 15 x 100W 150W at 8-ohms. This ones just for speakers and ...