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This is a modelling tool for A/B class audio stereo amplifier power calculation. Based on input variables it calculates the maximum peaktopeak and RMS voltage that the amplifier would be able to achieve, then applies that voltage to output impedance to get the RMS output power and peak current numbers. Next it calculates the total supply power and RMS current required from transformer. Basically you pick the transformer voltage and the tool will tell you how big the transformer and heat sink will need to be for building the maximum power amplifier at that supply voltage. You can then play with other input parameters to see what happens at different load impedances and allowable heat sink temperatures The model is somewhat simplistic. For example, the power supply ripple voltage is calculated for maximum power and then applied only once to derate the available output voltage. The transformer noload voltage drop to rated voltage at full load is assumed to be linear. The only input you can really use for oversized transformer is noload voltage coefficent Ripple calculation is done for 50 Hz mains, 60 Hz would have less ripple. Heat sink required thermal resistance calculation just looks at ambient temperature and max allowed heat sink temperature, and assumes free air environment. Junction temperature requirements of output devices are completely ignored. Do not trust any of the numbers to be absolutely correct, at best this tool will place you in the right ballpark with transformer, capacitor and heat sink sizing. 

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