I can tell you that my 507ux absolutely does not have adjustable taps.
It is my understanding from other members that generally Luxman does not, but Accuphase does.
As I think you understand, this feature has be built into the product by providing a primary power transformer that has the necessary connections.
This isn't saying that I know 100% of all Luxman or all Accuphase, so it may be useful to specify exactly which model you are thinking about.