You are going to have to call Krell. There are other things associated with conversion (fuses are going to have to be changed to a lower value at a higher voltage, e.g.).
Conversions are done either by switch, jumpers or a combination of both. Sometimes the jumpers are quick connected sometimes they are soldered. In any case, if you do not have a service manual or a schematic of the power supply you will be flying blind. Krell will probably want a few hundred dollars to do this but IMO it's money well spent.