For an amp, I suggest at least 2KVA (2000W) capacity. A quick Google led to APC Symmetra RM 5kVA (220/120V) as the pick of the heap but they're heavy for shipping and averaged around $700. I didn't see a smaller version. Generally used for large computer systems. There are plenty of cheap converters out there but you get what you pay for (away from our little audiophile world). Look at the weight.
Except for the Phillipines and South Korea, 220V is usually 50Hz. 50/60Hz usually isn't a problem for audio electronics, with the exception of turntable motors. Consult with the manufacturer to be sure. I know of no practical way to convert frequency, including a VFD, which are intended for electric motors.
International electrical "standards"
http://www.kropla.com/electric2.htm
Notice that Japan is either 50 or 60 Hz, depending on the region.
Except for the Phillipines and South Korea, 220V is usually 50Hz. 50/60Hz usually isn't a problem for audio electronics, with the exception of turntable motors. Consult with the manufacturer to be sure. I know of no practical way to convert frequency, including a VFD, which are intended for electric motors.
International electrical "standards"
http://www.kropla.com/electric2.htm
Notice that Japan is either 50 or 60 Hz, depending on the region.