I agree with nicleo.
The simplest way to realize the power supply you need is
building a linear power supply using the LM117 voltage regulator.
"The LM117 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 1.5A over a
1.2V to 37V output range."
You can choose the LM117 in TO220 package and you should use an heat-sink.
For the way to realize the linear power supply (transformer, rectifier, filter, voltage
regulator) I think you can find a great deal of documentation.
For the way to use the LM117 to adjust its output to your desired voltage, you can read the LM117 series data sheet available on National site.
Regards