Audio Matching · Max Power Transfer
Source & load
Enter source voltage, source resistance and load; power, efficiency and current appear live.
Power delivered
How to use this calculator
A source has an internal resistance; maximum power reaches the load when ZL = Zs, at which point Pmax = Vs²/(4·Zs). Enter the source voltage, source resistance, and load, and this tool shows the actual delivered power, the theoretical maximum, the efficiency, the current, and the optimal load. It's the quantitative form of "matching" — distinct from the Impedance Matching and Transmission Line tools, which focus on reflection and standing waves.
What it means in a real circuit
At the perfect match only half the available power is delivered to the load (50% efficiency) — the rest is dissipated in the source. That trade is acceptable where extracting the most signal from a source matters (microphones, sensors, RF front-ends) but is usually avoided in audio power stages, where high efficiency is preferred. Use this to understand the power/efficiency trade-off when pairing a source with a load.