Voltage Regulator Selection

Hi;

I have not dabbled much with electronics for a number of years, even though I used to be rather proficient. Currently, I'm thinking of building a power supply of 1 to 28v at around 5A.

I noticed that there are a number of different regulators such as the:

LM1084IT-ADJ 5A low dropout VR

LM2588T-ADJ 5A flyback VR w/shutdown

LM723 150mA adj + 2N3055 o/p for higher current.

Is any one device better than another or is it a question of cost and use?

thanks in advance...

For a max output of 28V the unregulated supply must be about 32VDC. If the max current is 5A and the output is set to a low voltage or is shorted then the series pass device must dissipate 160W!

One 2N3055 transistor is rated at 115W if its case is cooled to 25 degrees C somehow (liquid nitrogen?) but will be extremely hot at only 60W even if it has a huge heatsink.

Think about switching taps on the transformer so that the series pass device does not have a high voltage across it when the output voltage is set to a low voltage. Maybe automatic switching.
Or think about paralleling a few series pass devices to share the heat.