Using a step down transformer will not degrade sound quality if you are in 60hz area eastern part of Japan.Since bryston transformer are designed for 115v/60hz.
Luxman L-507U or Luxman L-509U Transformers are designed for 60HZ and 50HZ.I use to own a Luxman L507U.You can change the voltage to North American 115V by changing the jumper inside the unit when used in USA or Canada.Since you are in Japan Buy the Luxman High end L509U.L507U also is very good.
Luxman L-507U or Luxman L-509U Transformers are designed for 60HZ and 50HZ.I use to own a Luxman L507U.You can change the voltage to North American 115V by changing the jumper inside the unit when used in USA or Canada.Since you are in Japan Buy the Luxman High end L509U.L507U also is very good.