20-12A MKII

The Model 20/12 is a larger, more massive development of SME’s renowned Model 20/2. It accommodates nine-, ten-, and twelve-inch tonearms, with particular emphasis on the exceptional Model 312S. Compared with a typical nine-inch arm, the Model 312S offers 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.

Among the stiffest and lightest twelve-inch tonearms ever produced, the Model 312S addresses the long-standing challenge of combining rigidity with low mass. In listening, the benefits are immediately apparent, with exceptionally low tracking-error distortion and harmonic distortion contributing to an extraordinarily neutral and transparent presentation.

A turntable must also control extraneous vibration. These vibrations can originate from many sources, including airborne and structural energy from loudspeakers, groove modulation, stray electrical fields, and mechanical imperfections in moving components. The Model 20/12 tackles these problems through a combination of precision engineering and fundamental physics. Greater mass and stiffness reduce flexing and vibration, while carefully applied damping shortens the duration of residual resonances.

The Model 20/12 weighs approximately 33.5kg (73.7lb), a substantial figure for a turntable of its dimensions. This is significant because density, rather than weight alone, contributes to structural rigidity. The sub-chassis measures just 520 x 375mm (20½ x 14¾in), yet weighs 8.0kg (17.6lb). At 16mm (⅝in) thick, it resists low-frequency flexing, while efficient extensional damping attenuates high-frequency resonance.

The Model 20/12 has no discernible “sonic footprint”. Its sub-chassis is suspended on forty purpose-moulded O-rings, providing effective isolation from feedback. A large, centrally positioned fluid damper controls sub-chassis movement, giving a reassuringly stable platform when handling records on or off the platter.

A cartridge generates more than its electrical output. Mirror-image acoustic signals are reflected through the arm and record and ultimately pass into the sub-chassis as energy is dissipated. Conventional closed-loop designs do not fully address the differing phases of these signals. In the Model 20/12, the relevant structural interfaces have therefore been carefully engineered to provide transmission paths with the appropriate impedance.

This comprehensive control of vibration is fundamental to the Model 20/12’s design and helps explain its remarkable tonal and dynamic neutrality.

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 nine- and twelve-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.