Will Japan equipment work with USA current?

I don't have experience in what your planning but here is what I can tell you.

The east half of Japan uses 50 Hz and the west half uses 60 Hz AC, all at 100 volts, so nowadays all electronic devices made for use in Japan are manufactured so that they can run with either 50Hz or 60Hz 100VAC.

The Yamaha you mentioned should be able to run with both 50 and 60Hz. Might want to check just in case.

The problem is volts. If you really want to go ahead and buy the Yamaha, you might want to invest in a power converter which will pull the 120V down to 100V. Then you should have no problem using the Yamaha.

Or, you can ask your friend in Tokyo to TRY and purchase one which can take an input voltage of 120 volts. But I think he/she will have a difficult time doing this.

I have bought equipment from the US and used them in Japan and they worked okay, but ended up buying a power converter just in case. Im not sure about the other way around. Putting 100V into a 120V device, and putting 120V into a 100V device sounds like a different story. We are talking about high technology audio devices so I would be a little cautious if I were you.

As stated above, better check the specs of the Yamaha first.

Anyways, good luck.

According to an on-line article I just read, electrical voltage in Japan is @ 100 VAC vs 120 VAC as used in the USA. Also in Tokyo, the cycles are 50 Hertz per this article and not 60 hz as in the USA. But what you want to do is check the specs on the electrical power supply of this particular component you want to purchase. It's certainly possible that Yamaha could produce two differnt units, one for use in Japan and one for export to the USA. It's very possible the Japan unit may not work correctly here. Just be careful and check this out thoroughly before having it shipped here. You never know.