Project Description

SPIRAL GROOVE SG1.2

The SG1.2 body is comprised of four aluminum layers in two independent constrained-layer platforms. These two mirror-imaged assemblies, separated by four carefully positioned elastomers, function as a single platform. The feet, with Strange Attractor technology and low frequency damping, are attached only to the bottom layer. The second layer, which is separated by rigid damping material, provides a stable platform for the motor. The upper half of the SG 1.2 body isolates the platter and tonearm in a similar fashion. The bearing/platter assembly is attached to the 3rd plate from the bottom. The top plate, which is separated by a rigid damping layer, provides the tonearm mount. This allows motor, platter, arm, and the furniture the turntable rests on, to remain isolated from each other’s vibrations while maintaining critical alignment between them.

The unique Spiral Groove bearing is made from the same case hardened steel used for an F1 racing car’s crankshaft. Utilizing material made for high heat, high speed, high wear applications might seem unnecessary for a turntable bearing, but, it’s actually ideal for several reasons. For one, it allows to machine an extremely small bearing gap for superior platter stability. Secondly, since both bearing components are made from the same material, the clearance between bearing parts remains unchanged by temperature variations. In bearings made with dissimilar materials, varying rates of expansion and contraction result in variations in the stability of the platter. This can’t be controlled unless a heater is used to stabilize the temperature. Spiral Groove’s bearing design assures consistent high level performance without complicated compensation systems. And the steel used is so durable that the producer confidently offers a 20 year warranty.

The Spiral Groove bearing incorporates a steel ball and sapphire thrust plate so the entire weight of the platter rests on the very small contact area between the ball and sapphire. This spot is vulnerable to wear and is a source of noise. To further insure the bearings durability and smooth operation we use a custom designed magnet system that reduces the weight on the sapphire to about 2 Lbs. This is a major contributor to its smooth operation and low noise.

Like Strange Attractors, the SG1.2 platter is built with irregular shapes and carefully chosen materials. The Graphite and Aluminum assembly provides a non-resonant surface for the record to mate to. Energy transfers quickly from the record through the platter and is dissipated internally. A 14 inch stainless steel drive ring provides the inertia of a much heavier platter. The speed stability it provides can be heard in the SG1.2’s rock solid sound stage. The simple and reliable clamp assures close contact between the record and platter surface and helps flatten warped records.

The arm board has a lovely twist, so to speak: the SG1.2 arm board is fitted with a stainless steel bayonet mount. With the push of a button and a slight twist like a camera lens, it is easily removed from the turntable. This unique system provides the enthusiast fast and easy arm-and-cartridge swaps with accurate re-attachment. Once a cartridge and arm are set up and adjusted, detachment and re-attachment with the bayonet mount provides solid, locked-in, perfect alignment every time.

The extremely low residual noise floor of the SG1.2 reveals not just nuance, but sheer clarity. It breathes both low level and high level dynamics more convincingly. With very controlled authority it reveals low frequency extension and drive that is felt as well as heard. The SG1.2 exudes an authoritative calm that is a window into the soul of the performers. By removing itself from the equation it lets the vinyl—and only the vinyl—do the talking.

SG1.2 TURNTABLE

High mass, multi-layered aluminium body arranged in two layers with elastomer decoupling. Adjustable elastomer filled isolating feet. Unique bayonet arm board mounting system. Stainless steel platter drive ring, record clamp, pulley, and feet.

£27,500
  • Oversized stainless steel platter drive ring for increased inertia and speed stability
  • Inverted sapphire disc/hardened steel polished ball bearing for silent, long wear
  • Platter driven at rotational plane of bearing for wobble-free rotation
  • Spindle de-coupled from bearing for optimal mechanical isolation of record
  • Magnetic levitation system to reduce platter weight on the sapphire thrust bearing
  • Graphite and aluminum platter
  • Low durometer round belt
  • Quick-change bayonet mounted arm board
  • Electronically selectable speed control with fine adjustment: 33⅓ & 45 rpm
  • Low voltage/high torque AC synchronous motor with proprietary phase control to eliminate cogging.
  • Adjustable, decoupled, aluminum and graphite feet
  • Dimensions: 18.5” W x 15” D x 4.5” H
  • Weight: approximately 80 lbs.

Turntable Art and Science

Vinyl remains unsurpassed for reproducing music. To convey vinyl’s rich, nuanced potential, a turntable must have precise speed control and operate without producing mechanical or electronic noise. The goal is an un-compromised signal emerging from a silent background.

Noise Control

In the turntable body aluminum is the first-line of defense against errant vibration, storing and releasing energy in predictable ways. Assembled into a sandwich of differing thicknesses and separated by proven damping material, the result is a dense, stiff, and silent platform. The sound-absorbing, mechanically solid, yet isolated layers (i.e.: the motor, turntable bearing, arm-board, etc.) is found in SG1.2.

The platter is where the music begins. Spiral Groove’s platter is belt-driven at the contact plane of the bearing to eliminate wobble or oscillation. Both the SG2 and SG1.1 platters utilize a 14 inch drive ring of either aluminum or stainless steel to guarantee exceptional speed stability. Spindle and bearing are decoupled yet precisely aligned. A thick phenolic layer forms the bulk of the spinning disc, topped by layers of vinyl and graphite. These materials act together to dissipate the energy generated by the stylus in the groove, all but eliminating the “stylus talk” common to most turntables. Threaded record clamps, made of stainless steel or anodized aluminum (depending on the model), snug the record to the graphite to create intimate contact for vibration transfer. Together, these features dramatically reduce the turntables’ noise floor, giving unparalleled depth and specificity of image.

Stylus Talk

Pops and clicks on records occur when the stylus encounters a piece of debris in the groove and “plays” it as if it were part of the record. Such encounters also generate energy that, in some platters, is reflected back into the vinyl, moving the stylus and sending a second signal milliseconds after the first. This “echo” is so close in time that the pop or click is not heard as two pops, but as a louder and longer single event.

And, reflected waves don’t only come from dust or dirt in the grooves. The movement of the stylus through the groove also sends energy into the record which, on insufficiently damped platters, comes back through the record to the stylus, causing a higher noise floor and coloring the sound.

Spiral Groove spares no effort to prevent mechanical-electrical feedback. SG platters are carefully engineered and constructed to dissipate energy. And they do: SG platters dissipate reflected energy so it can’t get back to the stylus. Vinyl is a lot quieter and the music clearer when played on Spiral Groove.

Speed Control

All of our turntables use a 20 volt, AC synchronous motor driven by our proprietary outboard motor controller. The controller transforms AC wall current to DC and generates its own sine wave with switchable frequencies and adjustable phase to precisely control the motor. At startup the motor runs at full torque until it reaches speed when the current is reduced for smoother and quieter operation. The LED speed indicator flashes during start up, becoming steady when 33⅓ or 45 RPM is reached. Speeds are independently adjustable by 10% with 18-turn pots accessible on the turntable.

Please note: there is no further adjustment, calibration, or “tweaking” required to make the SG1.2 perform as designed. Once the table has been leveled and the speed checked for accuracy, it stays set up indefinitely. Get right to setting up the tone arm and cartridge (even these operations are easier and faster with Spiral Groove’s Centroid tone arm) and enjoy a new level of reproduction from your favorite records.