Here is a nice hack you may find very useful if you have a cheaper bench ... to using the 0-3 volts output from a digital potentiometer which is normally used to set the power supplies’ constant ...

[Guido Socher] built himself a great little bench power supply that’s able to put out 30 Volts at 2 Amps. Instead of taking the easy way out by putting a few taps on an ATX power supply ...