Probably not. Max voltage typically set by regulator itself, inconjunction with raw DC being supplied off transformer.
If you find that output isn't what it should be, look at rectifiers and filter circuitry between transformer and regulator input. In addition, look at heatsink on regulator (s). Excess ripple (leaky rectifier, cap) can cause ripple rejection to limit output of regulator(s). If heatsink is loose, or compound dried out, that can cause regulator to run hotter and possibly reduce output.
For a higher voltage, at near same power, consider use of single ended or variable boost converter.
~SD
