20-12A MKII Turntable

The SME 20-12A MKII is a suspended turntable fitted with the Series 300 Model 312S precision pickup arm. It is the larger, more massive development of the SME Model 20/2 and accommodates 9, 10 and 12-inch tonearms, with particular emphasis on the 12-inch Model 312S.

Compared with a typical 9-inch tonearm, the Model 312S produces approximately 27% lower angular-error distortion. Its wand and headshell are pressure-die-cast in magnesium, reducing their weight by 27g compared with equivalent aluminium components. The arm combines low mass with rigidity, helping to reduce tracking-error distortion and harmonic distortion for a neutral, transparent presentation.

Vibration control is central to the Model 20-12A MKII. Airborne and structural energy from loudspeakers, groove modulation, stray electrical fields and mechanical imperfections in moving components can all reach a turntable. Greater mass and stiffness reduce flexing and vibration, while damping shortens the duration of residual resonances.

The turntable weighs approximately 33.5kg (73.7lb). Its sub-chassis measures 520 x 375mm (20½ x 14¾in) and weighs 8.0kg (17.6lb). At 16mm (⅝in) thick, it resists low-frequency flexing, while extensional damping attenuates high-frequency resonance. The sub-chassis is suspended on 40 purpose-moulded O-rings to isolate it from feedback, and a centrally positioned fluid damper controls its movement when records are handled on or off the platter.

Energy generated by a cartridge can travel through the pickup arm and record before reaching the sub-chassis. The structural interfaces in the Model 20-12A MKII are engineered with transmission paths of appropriate impedance to manage these signals and their differing phases. The result is control of vibration through the turntable’s mass, stiffness, suspension and damping systems.

Model 20/12 configurations

MODEL 20/12
Supplied ready to accommodate a pickup arm, but without an arm fitted.

MODEL 20/12A
As above, but fitted with the Series 300 Model 312S precision pickup arm.

The accompanying graph compares the angular-error distortion of typical 9-inch and 12-inch tonearms, with the null points selected to equalise distortion at the maximum and minimum recorded diameters.

• Stable four point suspension.
• Sub-chasis suspended on eighty strands of rubber in the form of forty purpose moulded ‘O’-rings.
• Trimming screws for suspension adjustment.
• Central fluid damper controls sub-chassis motion and offers resistive ground-path for acoustic signals.
• For transport lock down screws secure the sub-chassis and seal the damper.
• 19mm diameter main spindle machined from high-chrome steel hardened, ground and super finished. Runs in a sealed oil bath.
• Reflex clamping system minimises record resonance.
• 6.5Kg (14.3lb) machined platter with unique Isodamp face.
• Generous use of extensional damping and resistive loop construction ensure sonic neutrality.
• Adjustable ball feet with optional compliant inserts.
• Four jacking screws built into the sub-platter allow the thrust bearing to be off loaded for transit.
• Driven by a 3-phase, 6 pulse, inductance motor, with 8 pole Neodymium magnets and 3 integrated Hall position sensors.
• The power supply houses an electronic controller using a high performance microcomputer, optimised for motor control. Closed loop speed control is implemented using a pseudo sine wave commutation sequence and a proportional-plus-integral (PI) algorithm.
• New design incorporates a 4 layer surface mount technology pcb with on-board user adjustable speed variation control.
• Large diameter strobe disc supplied allows precise adjustment of standard speeds.
• Speeds ranges: 33.3, 45 and 78 rpm.