well, quite a tricky problem.....
i dont know any ic regulstors for more than 24 volts@1-1.6amps, but u can find regulators @4amps and use them...
about the voltage i think u can do something llike a symetrical regulator....
use a 24-0-24 volts transformer, 2 bridge regulators, 2 capacitors and 2 regulators, a positive and a negtive one, so at the exit you will have
-24V, 0V, +24V and between the positive and the negative u will have 48 volts, bu t it's tricky....
another way is to use a power transistor such as 2n3055 or mj2955(they hold 15A) and create a regulator....
but the trnsistors above have a low hFE so u will need another transistor to control it and some reference voltage....
but u decide anout the solution u will pick and we'll try something./
A!, i have a lot of schematics but, some hold 3 or 5 amps, but voltage as low as 25 volts, or some schematics for adjustable 0-50v,/ 2 amps and it's quite complicated