Sales-wise not as successful as the original R1 combo but a fairly different drive which replaced the BU + KSS-190 introduced in 1987 for more "G" compound drive base, a newer 3x BSL motor unit with a cleaner mechanism layout, equivalent to that of the CDP-X779ES and CDP-X707ES players.
This new mechanism allowed even better vibration control and damping and Accuphase, naturally, used it in its own units.
The power-supply was upped and all boards upped and redone as well : the CDP-R1a wasn't a simple re-take with a redesigned front but a completely new development.
The real sonic updates were however reserved for the DAS-R1a d/a unit.
As for all of Sony's top units, the fit, finish, work on colors and textures is unbelievable and puts all other brands right next to the DIY amateurs - but you got to see and use them to fully grasp that element.
Perhaps the near-identical looks were a mistake (market-wise) but this still is an excellent combo which was kept available along with the 1992/93 CDP-R10 and DAS-R10 for those who couldn't shed 2,000,000¥ for the latter. Although... at 700,000¥, the R1a combo wasn't exactly cheap either.
Very successful however it was among japanese audio reviewers : two thirds of them had one as "reference" until the early days of SACD (and beyond).
Unlike the CDP-R3 player, the R1a combo was vaguely exported outside Japan, much after its homeland launch.
The exact production run should be around half of the original CDP-R1 / DAS-R1 : 650 combos made, tops.