Sony CDP-X559ES
Sony CDP-555ESA
(1991 - 1992)

Part of Sony's worldwide bestsellers. It also seems the xx9 units were the ones that sold better, better than the CDP-X555 or ultimate CDP-X505...

For half the price, you'd get 90% of a CDP-X779ES.
What you didn't get was ultimate details: Twin-Core transformer, XLR outputs, the coaxial digital out or a super-beefy power-supply.
What you did get on top of a truly unbeatable bargain was a complex system of CD filing called "Custom File", all sorts of programming modes... and a lot more buttons on the front.
However, the rest is nearly the same as a CDP-X779ES: "G" base drive, "G" tray, GIC analog LPF, Sapphire bearing and BSL motor, copper-plated chassis 'n all - and the bargain worked very well for there are thousands of X559ES and 555ESA still playing around the world.

The digital filter is a CXD-2560 ; the digital to analogue chip is a CXD-2562 and the laser block a KSS-272A, the latter being used on all players of the series (X779ES, X559ES, X339ES) and quite a few others.

Available as CDP-X559ES worldwide and as CDP-555ESA in Japan ; the X559ES in black with matte square sideburns or gold with shiny rounded sideburns, the 555ESA with rounded sideburns whether the player was black or champagne.

12,5 kilos of long-lasting and affordable high-end.

ABOVE, left to right
CDP-X779ES > CDP-X559ES > CDP-X339ES
(CDP-777ESA > CDP-555ESA > CDP-333ESA)
The drive mechanism is identical between the 779 and 559 with only the transformers, audio boards and general structure simplified. The comparison between the 559 and 339 shows the same transformers but a different drive (I believe inherited from the previous CDP-X333ES), even more simplified audio board and no copper-plating of the chassis.

RIGHT
Three of the common features between the 779 and 559 : tray locking system, sapphire bearing and ceramic insulators.