Step 1. Measure the input power of amplifier
To determine the efficiency, you need know how to measure the input power of a device. Use the formula P=V*I. You can easily measure the voltage of the amplifier and the current coming into the amplifier using a multimeter or an oscilloscope. The product of voltage and current gives you the input power.
Step 2. Calculate the output power of amplifier
Output power is the second important factor to calculate the efficiency of an amplifier. Take the formula P= V2/R, where V is the output voltage and R is the resistance. Simply take the square of speaker output voltages and divide it by the resistance (ohms). This will give you the output power.
Step 3. Determine the efficiency
Using the final formulaEfficiency = Output Power/Input Power, you will be able to find the amp’s efficiency. Divide the output power by input power and the outcome will tell how efficient your amplifier is.