The New Reference

The Thorens New Reference is the result of our strive for the perfect rendition of music recordings. The electrical signals in a turntable are created by mechanical vibrations of the stylus of the cartridge while it moves along the grooves of a vinyl record. These vibrations are converted into the sound.

In exactly the same way all other mechanical vibrations of the turntable are processed and lead to distortion and other unwanted effects. The sources of these vibrations are for example building vibrations people walking around the sound waves of the music and self-generated vibrations from the turntable itself. Since it is not possible to distinguish between the actual music vibrations and parasitic disturbances these must be avoided as much as possible.

The Thorens design team around Helmut Thiele who is responsible for the construction and design of the new Reference have taken on this challenge.

With the Thorens New References for the first time ever a turntable is designed and optimized from scratch together with a fully active vibration isolation system. Thorens teamed up with the German company Seismion which is internationally renowned for its class-leading active vibration isolators to create a turntable that is designed around the vibration isolation system as an integral part of the system. Seismion fully exploited its expertise in active isolation systems used for semiconductor industry nanotechnology and scientific laboratories to create a vibration isolation never seen and experienced in turntables before.Sky-Hook damper

The active vibration isolation is based on piezoelectric acceleration sensors with an extremely high sensitivity and an all-linear electronic control circuit to generate unrivalled low noise- and distortion-free control forces. This sophisticated mechatronic system is based on so called Sky-Hook-Damping and isolates disturbances already below 1 Hz and reduces them to less than 1% (-40 dB) at frequencies of 10 Hz and above. Such a performance is far superior to any other isolation (figure 1). This figure shows the comparison of the active isolation system – Sky-Hook-Damper – and a high-performance Air Spring. Especially at the critical frequencies around the resonance the active isolation has a performance which is up to 100 times better. At 10 Hz it is still about 17 times stronger isolated than with an Air Spring. Other dampers like rubber mounts are on a much lower performance level and not shown in this comparison.

The entire system is designed so that the center of gravity (COG) is close to the isolation plane. This greatly reduces the coupling of horizontal vibrations and tilting movements (Figure 2). Furthermore, the chassis itself is resonance-free thanks to its layered structure of highly dampening materials.

The result of the vibration isolation is pure music, the likes of which one rarely experiences. The effect goes far beyond simply eliminating impact sound vibrations. In fact, even the smallest vibrations, from the nanometer to the picometer range, are still efficiently isolated thanks to the contactless actuators. The system also follows music with high dynamics between quiet and loud sequences extremely quickly, as the active control forces stabilize the system and lead to an immediate decay of the vibrations. An adaptive leveling system that precisely balances the turntable to within 20 micrometers completes the active isolation system.

The other fundamental part of every turntable is the drive unit. The ultimate goal is to realize the perfect and constant rotation speed of the platter. This concerns both the absolute speed and modulations of the speed around the mean value also called wow and flutter.The Thorens New Reference features a high-quality German-made 3-phase synchronous motor which is driven by three all linear power amplifiers with 120° shifted sine signals. The motor torque is transmitted to the platter by a belt (figure 3). The hydrodynamic bearing is optimized by use of lubrication theory equations. In this context the Sommerfeld-number is used which describes the thickness of lubrication film and the diameter of the bearing. This number is named after german physicist Arnold Sommerfeld who conducted several fundamental research in the field of hydrodynamics. A small Sommerfeld-number means the bearing is centered already at very low rotation speeds which minimizes the wear and ensures minimum out of center errors like eccentricity and whirl. The hydrodynamic bearing is made and hand-finished in Germany.

Together with the innovative active damping technique the belt-driven approach has several significant advantages:

1. Unlike Direct Drive systems the turntable platter is isolated from the drive motor because of the elastic belt. The high inertia of the platter is therefore efficiently utilized and helps to passively remain a constant velocity of the platter. Moreover any fluctuations from the motor are strongly supressed by the platter/belt second order low-pass characteristics.

2. A common disadvantage of belt-driven systems is the potential resonance of the platter which is observed as wow and flutter. The rotational inertia of the platter forms together with the elasticity of the belt an oscillatory system. The resonance frequency is typically about 4 Hz but depends on the actual parameter values of the system. The orange graph in figure 4 shows a peak around 4 Hz where all disturbances are strongly amplified. This means that the rotation speed of the platter is no longer constant but modulated with 4 Hz around the mean velocity. This effect is known as wow and highly undesired especially since the human ear is most sensitive to this frequency range. Figure 5 displays the weighting curve as described in DIN 45507 or IEC 386. The maximum of this weighing unfavorably coincides with the typical resonance of the platter / bearing system. Vibrations of the platter are excited mainly by the friction in the platter bearing by a not perfectly circular platter by irregularities of the belt and by slip between the belt and platter which is necessary to transmit the torque from the motor. The orange graph sharply drops of for higher frequencies. This is the desired effect of the platter inertia.

The Thorens New Reference features an innovative and highly effective active damping system by Seismion. The deep knowledge and experience with sky-hook-damping systems featured in the active vibration isolator “Reactio” are used for the all new active damping approach of the platter.The rotation speed calculation of the platter is based on two ultra-high-precision quartz-oscillators with a long-term stability of max. 3 ppm over 20 years allowing for a safety cross check and reliable speed control over the life time of the New Reference. In fact it means that the absolute speed remains within a range of 33.3332 to 33.3334 rotations per minute over 20 years.