12V-220V(ac) to 12V-50V(dc)

[raszvan]

i wanna build a car amp....i found a few cheap convertors..but they are 12v to 220v...can i modify a 12v to 220v converter to get 50v out of it(+ 0 -) or at least to make the 220 output in to 110V+ 0 110V-??