SME Model 20/12 Turntable
offered in Los Angeles by Brooks Berdan, Ltd.
A larger and more massive version of our well known Model 20/3. 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 74lbs, 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” by 14 3/4″ but weighs 17.6lbs. Its 5/8” thickness resists flexing at low frequencies while high frequency resonance is attenuated by efficient extensional damping.
Can fit 9, 10 and 12″ arms, but the Model 20/12 was specifically designed together with the Series 312S tonearm.
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.
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 weight is 14.3lbs. 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.
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 5.5 lb weight as well as being isolated on urethane mounts that are adjustable for accurate belt positioning.
The electronic controller uses a high performance microprocessor, optimized 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.
Dimensions and Weight
Dimensions: 14.7″ x 10.6″ x 5″
Net weight: 78lbs
Shipping weight: 100lbs