If power consumption is not an issue, there are a variety of simple ways to drop 24V to 12V. Zener diode, 7812 or other linear regulators... But if the circuit is drawing sizable amount current (like mine draws about 180mA current), then (33-12)*0.18 = 3.78 Watt power will be wasted. Note that the 33VDC comes from rectifying 24VAC. In fact, there will be more because the 12V to 5V conversion will waste another (12-5)*0.18 = 1.26 Watt. That's a total of 5 Watt. So in this case switching regulator is more efficient.