@Groove Doctor
Sorry to be reviving this thread - but i'm in a similar position (currently living in Japan/100v, and may at somepoint move back to Europe/230v).
Did the jumper-switch work? did the amp function normally thereafter, or were there fireworks?
The labelling on the version I have is very adamantly saying "100V only operation", but the circuitboard looks the same, including the 115/230 jumper
Thanks in advance to anyone who could confirm