Separate step-up transformers and adaptor of the quite very much too rare kind and plug-in type.
The 8020 and 8030 differ only in step-up ratio, maximum input and primary impedance ; specifications and construction are identical for both, and very high-end, too.
79% nickel, 5% molybdenum and iron core smelted in vacuum with a pure hydrogen gas packed into an acrylic case filled with silicon oil.
Despite the toroidal structure doing away with most exterior magnetic fields, multiple electromagnetic shields made with a super-permalloy of 78,5% nickel are used.
Wiring and Winding
Extra-fine threads of Litz wire, 99,9% pure silver wire for the primary ; parallel wiring added for the 8030 ; coaxial terminals make the contact between the AD8000 and the transformers to avoid exterior inductance.
The common features are exceptionally clean and extended reproduction, linear frequency response and low distortion up to almost 1000mV.
The Type-8020 and Type-8030 transformers came first, as high-end options for those owning a 5C50 Laboratory Reference Standard preamp.
Although the latter sold well, then came the AD8000 adaptor because... not everybody had a 5C50 !
Luxman being Luxman, the presence of a receiving terminal on its preamps wasn't over extended (to say the least) so as to help selling more 8020s and 8030s - either you are Lux or you are not.
It was however inlcuded in the 1978/1979 extra-rare L-11 integrated.
The 8020 and 8030 remained available as options for the 1978 CL36 tube preamp, 1978/79 L-11 integrated and the 1980 solid-state C-5000a, joined by a Type-8025 at some point.
All four objects are very rare.
See one AD8000 & 8020 at hifi-do's and a Type 8025 here.