So a pretty great design. Simple, and very efficient.
If you want to build this, be sure to use resistors with a wattage rating that match your transformers max output.
Assuming a 14v 3A Transformer:
Your Amplitude would be 20v(since the app doesn't compensate for RMS I have set up the transformer with a 20v supply.
If each resistor is 2W that gives you 24w of dissipation and 60ohms of source resistance.
At 60ohms of source resistance, your output will sit at around 15-15.8v with a max source current of about 330ma.
The point at which the voltmeter is connected would be your output.
