A regulator with no zeners diodes or any kind of voltage regulator just a resistor and a capacitor to sink in the ripples. Even at 6V pk-pk input ripple the output is veeery smooth with ripples less than 100uV pk pk at 15W. Theres one minor problem though. The 22uF cap will charge through the 3.3Mohm resistor in about a minute or so.
