A microwave oven transformer can be used for a powerful low voltage supply.
“Continue reading” for construction details of this modified low voltage transformer.

                            

Left photo shows removing the HV windings the hard way. Usually easiest to hacksaw off the winding flush then use a block of wood and hammer them out. Can’t be done easily with this vertical winding style however. Middle photo shows the 0.83 volts AC (RMS) for a single turn at the rated 240 V AC input. Right photo shows 13 turns being one side of a centre-tapped winding. This gives 11.8 V AC which will be 23.6 V AC which after the diode bridge rectifier will be 23.6 * (sqrt 2) = 33.6 volts. This will be reduced by the voltage drop of the rectifier to about 32 V DC peak.

Left photo shows the full 26 turns centre-tapped giving 22.86 V which is a little different to the 23.6 above due to slightly different input voltage. Right photo shows the addition of heavy gauge windings of 4 + 4 + 7 windings in series to give 12.72 V AC.
This allows the many AC voltage combinations from 3.3 V to 35 V. Arranging selection of these is now the consideration, along with a range of DC voltages at an appropriate cost i.e. nearly zero.