Anyone use 100v or 220v gear with a transformer?

Interesting and informative answers from everyone. Most agree (including the manufacturer's Japanese representative) that a step down transformer can be used without problem.

The issue of sonics is the quagmire. Other than the mention of degraded sonics here, the only other mention of this has been from a US dealer. Clearly, there could be an agenda with the dealer, but I also am not willing to dismiss the possibility of degradation.

I have decided to forego purchasing the Japanese unit.

I have decided to forego purchasing the Japanese unit.

Sorry to hear you have been frightened away from your plan. I agree with Pauly that bigger is better. Most Transformer cores saturate when used close to their rated power and that is when you get annoying humming from DC offsets and potential degradation in the quality of the power.

I am actually quite surprised that the Japanese unit will not function with 120 Volts if it is rated at 100. I would have expected the Japanese device would tolerate the slightly higher voltage. (Nominal power is allowed to vary about 5% from your utility and devices are normally designed to function properly a further 3% to 5% outside this range (due to further voltage drop in the home). I would expect a similar kind of tolerance for Japanese equipment.

Signal degradation is very unlikely.

The ability of the 100v unit to function on 110-120v either straight to the wall or with a step-down transformer was not the issue. Sonic degradation was an issue, as was safety and warranty service, which would have required shipping the unit to Japan for service if it was required.

I spoke with someone today who is intimately involved with tube gear, and who has no agenda whatsoever, and his advice was to buy the 120v USA version.

I'll have to admit, it was difficult passing up the opportunity to buy the Japanese model for 45% less than the US version with 120v transformers (and nothing else different), and because of the large price differential I will likely explore other integrated amplifiers.

If you run a 100v unit on the 120v USA standard, don't expect your unit to last too long...and forget about your warranty! The USA standard is 120v +/- 5% [or 114v to 126v]. So at best, you'll be running at a 14% over-voltage; at worse, a 26% over-voltage...OUCH!

Point made.

Moving on...