voltage transformer and tube gear

A step up transformer for the preamp could be considered, because the pre is generally low on powerconsumption. The poweramp however is an entirely different story and you would probably need quite a hefty unit to do the job properly without serious losses in dynamics. I'd rather suggest, you contact your dealer or the manufacturer direcly on how to change the voltage for your units. More often than not that can be done quite easily by someone qualified to do the job. Hope this helps you on a bit.
Cheers,

Detlof,
I truly apprecaite your helfful advice. If I were to buy a 50watts tube, what would be the appropriate size for the transformer? Does this apply to both tube and solid state?
Thanks again

Most amps have a power consumption rating. Class A amps will draw a steady current until forced to A/B. Class A/B amps fluctuate draw on demand. Some, like a Carver Lightstar (300 wpc) can draw up to 15 amps at peak, however unlikely. As a guideline:

50 wpc stereo = 300 VA (watts) input, roughly 3 amps,
100 wpc = 500 VA, roughly 5 amps

As a general rule a transformer should be double the VA of the demand but 2 KVA would be the minimum I would suggest, even for a small amp. Honest three KVA, but not all, would allow 15 amps of most household outlets and weigh about 75 lbs. Wired for balanced AC, derate by half. No transformer will convert Hz but that shouldn't be a probelem for pre/amps. It could be a problem for a CDP or DAC but most of those can be either 50/60 Hz.

I use a 120 lb,5 KVA tranny for 20 amp balanced.