Just a different motor, plinth, platter and bearing.
Otherwise they're the same
From the Vintage Knob:
Mostly different from the SP-10MKII bestseller is... everything !
The drive itself sees its weight doubled from 9,5kg to 18kg. More precisely : the platter of the MK3 weighs as much as the entire MK2 drive.
The SP-10MK3 is mechanically based on Technics' SP-02M cutting lathe so this explains that.
Starting torque of this new ultra-low speed brushless DC motor allows a 16kg/cm spec - twice as much as that of the 1975 SP-10MK2 and... sixteen times as much as the original 1969 SP-10 !
This means a full speed ahead in 30° of a full rotation or 0,25s.
The inertia moment of the 10kg platter is of 1,1 ton/cm2... The platter has a 1,5cm copper alloy core (inner platter), supported by a diecast aluminium outer platter.
1,1 ton/cm2 is, btw, the equivalent of 1000 tonearms all tracking at 2g.
The power supply houses a very beefy and resin cast transformer (inside) and the speed and start/stop controls plus the ± 9,9% pitch control in 0,1% steps (outside).
You can see design iterations for this power supply under Knobber Image #3.
The recommended tonearm and base were the EPA-100MK2 and SH-10B5 (but the original EPA-100 can work just as well !)
The boosted signal-to-noise ratio reaches 92db - not as much as an Exclusive P3 but respectable just the same.
There is however number's magic here : the EIAJ changed its DIN B measurement method in 1981 to "better measure what the ear hears".
This had the effect of raising signal-to-noise ratio by about 20dB, whatever was measured.
The SP-10MK3, or any other component for that matter, doesn't have an actual 20dB boost in s/n ratio : physics have their limits.
When compared to the SP-10MKII : if measured with the same referenced method, they'd measure about the same. And 78dB or 80dB is already plenty enough !