Voltage question...

It is good advice to let krell do the modification if you have never done something like this before. I have not seen a schematic of this Krell amp but if I was a betting man, I would guess that it may be as simple as changing the primary taps on the power transformer, but I am only speculating. Good luck to you!

I also live in the UK and have done it before. The unit must have been more than 6 months in the US for Krell to want to do the modification. Its actually a chip that measures the frequency and locks/unlocks the system so you canot do it yourself
Regards

If the unit is still under warranty check with Krell and make sure it is transferable to the UK. Not all warranties transfer between countries even if it's transferable between owners. Cheers - Dan