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SME Model 20/12

SME Model 20/12

£17,250.00£18,250.00

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SKU: sme-model-20-12 Categories: , Brand:

Product Description

The Model 20/12 is a larger and more massive version of SME’s well known Model 20/2. It will accept nine, ten and twelve-inch arms but is especially directed at the exciting Model 312S. This offers a performance some 27% better than a nine-inch arm in respect of angular error distortion. The wand and headshell are pressure die-cast in magnesium and are 27g lighter than they would be in aluminium.

Probably the stiffest and lightest twelve-inch arms ever made these dual problems are at last addressed and on listening, the benefits of minimal tracking error and harmonic distortion are clearly revealed. A turntable should address the problems of extraneous vibrations. These emanate from numerous sources including air and structural vibration from loudspeakers, groove modulation, stray electrical fields and mechanical imperfections in moving parts.

In the Model 20/12, superb instrument quality machining is allied with fundamental physics. The higher the mass and stiffness of a body the less it will flex and vibrate; the duration of a vibration can be shortened by suitable damping.

Model 20/12 weighs approximately 33.5Kg (73.7lb), significant in relation to its size because it is density that matters. For example, the same weight of metal spread over a large enough area would be aluminium foil! The sub-chassis measures only 20 1/2” (520mm) by 14 3/4” (375mm) but weighs 8.0Kg (17.6lb). Its thickness, 5/8” (16mm) resists flexing at low frequencies whilst high frequency resonance is attenuated by efficient extensional damping.

Arm
9, 10 and 12 inch arms, but designed to compliment SME’s Series 312S tonearm.

Suspension
No sonic footprint, the sub-chassis is hung on 80 strands of rubber in the form of 40 purpose moulded ‘O’ rings. An ingenious method of anchorage allows them to be removed or replaced instantly.

Damping
A large centrally placed fluid-damper disciplines sub-chassis movement with a pleasing sense of security when handling records on and off the platter, offering a resistive ground-path for acoustic signals.

In addition to a cartridge’s electrical output, mirror image acoustic signals reacted in the arm and record, will pass into the sub-chassis in the course of dissipation. However the usual closed loop design does not address the problem of their differing phase so in the Model 20/12 the structural interfaces concerned have received special attention to provide paths of the required impedance.

This control of vibration is fundamental to the design of the player and goes much of the way to explaining the stunning tonal and dynamic neutrality that it exhibits.

Platter
6.5Kg (14.3lb) platter. The face is machined with a fine scroll found to interface better than a plain surface. A substantial reflex clamp ensures maximum contact with the platter even when severe record warp is present. The sub-chassis/arm mounting board interface is extensionally damped and the mounting board is reversible to allow mounting of nine inch pick-up arms when necessary.

Motor
The turntable is driven by a 3 phase, brushless outrunner motor with 8-pole Neodymium magnets and 3 integrated Hall effect sensors and virtually vibrationless by reason of its 2.5 kg (5.5 lbs) weight as well as being isolated on urethane mounts that are adjustable for accurate belt positioning.

Speed Control
The electronic controller uses a high performance microprocessor, optimised for motor control. Closed loop speed control is implemented using a proportional plus integral (PI) algorithm. Fine pitch speed adjustment allows increments/decrements of +/-0.01% of selected speed. Speed ranges: 33.3, 45 & 78 rpm.

Custom Specifications

DIMENSIONS
Width 520.0mm (20.47”), Depth 375.0mm (14.76”), Height 173.5mm (6.83”)
Platter Diameter: 325.0mm (12.80”)
Spindle to Arm: 295.60mm (11.64”)
Net Weight: 35.5Kg (78.1lb)
Shipping weight: 45.5Kg (100lb)

SPECIFICATION
The turntable is driven by a 3-phase, 6 pulse, inductance motor, with 8 pole Neodymium magnets and 3 integrated Hall position sensors.
The electronic controller uses a high performance microcomputer, optimised for motor control. The Hall position sensors on the motor provide accurate feedback to the micro controller allowing very accurate and stable speed control, including 33 1/3, 45 and 78rpm. The reference oscillator is a 10MHz quartz crystal, which is multiplied by 4 to produce an internal microprocessor clock speed of 40MHz.
The driver stage has CMOS buffers/MOSFET drivers with 1.2 Amp peak drive capability.
The power output stage is six high power complimentary Mosfets in a 3 Phase Bridge Driver configuration.
Closed loop speed control is implemented using a pseudo sine wave commutation sequence and a proportional-plus-integral (PI) algorithm.
The design incorporates a 4 layer surface mount technology pcb with on-board user adjustable speed variation control.

SPEED RANGES
33 1/3, 45 and 78 rpm.

Additional information

Tonearm

None, 312S

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