Notice one thing about the tracks: they're not the 1,067 mm gauge tracks you find in most of Japan. They are 1,435 mm tracks because of the need to accommodate the Yamagata Shinkansen trains between Shinjo and Fukushima before joining the Tōhoku Shinkansen line.
I actually like the way these older trains run without switching inverter noise. On a DC supply the older motor control involves resistances which are inefficient, but this line has AC supply, so a multi-tap transformer is an efficient and silent method of control.