Depends what you want to do with it, and you don't mention how much power you need.
One of the problems is that you specify a much lower voltage spread in the higher voltage, which means a transformer is unlikely to work (and a transformer is probably the simplest solution), a 1:3 ratio works fine for the 8 to 24, but gives 14 to 42 to for higher voltage.
Solutions other than a transformer are more complex.
Please tell us how much power you need, and more about the target voltage(24-30) use,
cheers,
Richard
