I would eer on the side of caution and use a stepdown transformer. The mixer does not draw that much power so you would only need a small transformer. Operating 100V equipment on 115/120V nominal puts it at 15-20% above the operating voltage rating. If you account for AC supply voltage peaks, that's adding another 2-3% on top of that. By now you see where this is going. I would not oparate my equipment at 20+% above its rating.