As the stylus of a cartridge moves through the groove of a vinyl record, the vibrations created by the groove are converted to electrical signals through a coil in a magnetic field. The electric signals are carried along wires to the amplifier which enhances the power of the signal. Since vibrations are converted into a signal which eventually is converted into sound, we can see that any extra vibrations that are picked up by the stylus influence the purity of the signal and hence the sound quality.
In a mechanical system such as a turntable, energy in the form of vibration over a large range of frequencies is present. Some vibrations originate from the external environment and are transmitted through the building structure and through floor into the playback system. Other vibrations are caused by people moving near the system or by bass transmitted through the floor. Some vibrations are transmitted through the air and some vibrations originate from the mechanical system itself like the motor, the bearing or the actual stylus interacting with the record. Vibrations interact with each other, resulting in all sorts of complex vibration patterns within the playback system. Ultimately these unwanted vibrations mix with the vibration of the stylus in the groove, causing distortion and unwanted sonic artifacts.
Therefore, the Holy Grail of analogue audio design is to eliminate as much of the unwanted vibration (resonance) as possible so that the stylus can interact with the groove and ONLY with the groove, thus picking up all the musical information without interference or influence by any other phenomena. It is actually impossible to completely eliminate all unwanted vibration, but the more successful you are in reducing it, the better the sound quality achieved. All turntable designs attempt to deal with these resonances to some degree.
What makes Döhmann Audio unique is the extreme effort we go to ensure that these unwanted vibrations are kept away from the signal path.
For example, to isolate the Helix One and Helix Two turntables from ground transmitted vibration, instead of using common suspension systems based on springs, rubber, plastic, foam, air or spikes which have serious limitations, Döhmann Audio use a revolutionary Negative Stiffness Mechanism (NSM) from MinusK Technology USA who developed this isolation technology for electron and atomic force microscopy and other applications that are very sensitive to resonance. This significantly mitigates low frequency vibrations up to approx. 100Hz.
If we simply place a turntable on a MinusK platform (as many people do), it helps to reduce low frequency vibration but frequencies above 100Hz get transmitted through the platform to the turntable. The turntable’s own built-in isolation system then needs to be specifically tuned to deal with these higher frequencies. Most turntables are not designed to specifically sit on an isolation platform and work completely in harmony. One example is the rotating platter mass at 33rpm will have a natural frequency of 0.55hz. So the turntable itself will generate its own “seismic” vibrations. This is a major source of noise being created by the very system a designer is trying to isolate from the external world.
Then add the greater issue of tall heavy platter systems sitting high on a 6 degree of freedom (x,y and z axis) compliant low frequency isolation system like the MinusK and you will see this causes precessional instability due to the high centre of mass of the platter behaving like a spinning top children’s toy toppling about. This is why just adding a MinusK to your existing turntable is not the same as the Helix architecture.
The Helix 1 and 2 cleverly distribute the table mass around and below the MinusK internal mechanism to lower the center of mass and deliver unparalleled stability in the platter precessional modes via a low-slung greater mass than the platter mass. This is one reason why the Helix is “not just a platter stuck on a MinusK”. The spinning platter mass is being stabilised in a greater chassis mass distributed low and evenly.
Solid mounted turntables do not isolate well. They try to use mass to absorb vibrations. Some demonstrations might show vertical stability based on the floor and bench mounting being solid in the vertical plane but on flexible wooden floors these designs suffer. Horizontal vibrations are also present in the environment (just ask anyone living in tall buildings or in cities affected by the tectonic forces that cause earthquakes and tremors). This problem also affects laboratory instruments such as electron and atomic force microscopes which like a phonograph cartridge are very susceptible to vibration intermodulation distortion.
In addition, the higher frequencies often interact with the turntable’s own isolation system which causes further problems. To avoid this, Döhmann Audio worked with MinusK to create a special version of the platform that is tightly integrated into the turntable chassis to create a seamless transition from low to high frequencies. The isolation system is a part of the entire mechanical structure so there is no unplanned interaction between two disparate systems.
The critical question then becomes, what about the frequencies above 100Hz?
Here’s where the Döhmann technologies come into their own. The Helix turntables have a mechanical crossover system which creates a smooth continuous pathway to channel vibrations of higher frequencies away from critical areas on the turntable. The proprietary TDS technology uses a pre-stress accumulation release (PAR) strategy to isolate and dissipate vibrations inside the chassis.
Furthermore, the motor, bearing and armboard are on separate plates that are significantly isolated from each other, making it extremely difficult for energy to transfer between these critical areas. A unique arm board damping technology is used which further dissipates energy and is a major contributor to the sound quality.
We call this entire wholistic approach our Micro Signal Architecture© (MSA). MSA is a cohesive design approach that uses the most advanced available techniques to remove physical and mechanical vibration and electrical noise.
So well beyond simply integrating a MinusK isolation platform into a chassis, Döhmann Helix One and Two turntables incorporate the latest resonance mitigation technologies available to ensure that the stylus of your cartridge has the greatest chance of extracting the vital information from a vinyl record without suffering the effects of unwanted resonance. These technologies have never been applied so comprehensively to audio playback systems before and are not available any other commercially available brand of turntable.
Is it worth all this cost and effort? If you are searching for the most direct connection to the emotional message of the music, if you are looking to experience the purest enjoyment of your analogue music system… we think so!
Döhmann Audio draws on many design influences from the aeronautical, automotive, architectural and technological design styles to ensure the products are functional and aesthetically pleasing. The aesthetic quality of a product is very important because products we use every day affect our person and our well-being.
Products that have well executed functional design can also be beautiful. Great design makes a product self-explanatory. Needless bling is avoided and if a sonic parameter is affected by a design feature then it has to be incorporated to improve the sound.
During his time as an engineer and reliability analyst at an Australian airline, Mark worked on aircraft systems and components where reliability was extremely critical. It was during this chapter in his professional life that he made the realisation:
GOOD DESIGN IS AS LITTLE DESIGN AS POSSIBLE
Our philosophy is that a design should be honest as discerning customers who love music can quickly spot gimmicks. Honesty in design language does not attempt to manipulate the consumer with promises that cannot be kept.
A quality turntable is an investment for the long-term. Good design is long lasting even in today’s throw-away society. A Döhmann design is thorough down to the last detail to ensure the sound reproduction is as faithful as possible to the original source. Nothing more, nothing less.
The analogue audio market has undergone a significant renaissance in the last 15 years. Contrary to the predicted demise of the turntable heralded by the release of the Sony CDP-101 in 1982, the analogue market has withstood the test of time and has seen steady growth since 2000.
Each form of media, digital or analogue, is a facsimile of the original performance. No media is truly inclusive of every detail of the performance. However, from a sound quality perspective, the question is are we extracting all the available information from the media?
What makes a Döhmann design different?
It is the Döhmann Audio approach to micro-detail retrieval that sets the designs apart from the majority of the market offerings.
This has been the main goal of all turntable designers throughout the history of audio and remains the goal of most serious turntable designers today. Ultimately, it is a matter of how much effort are you prepared to put into your design? How important is it to you? For many designers, it may not be commercially viable to start fresh and invest the resources into new research, testing and measuring. This is why the majority of designs offered to the audiophile market are based on old technology & methodology with a fresh aesthetic.
At Döhmann Audio, we have listened to most of the modern high end designs which are well reputed and believed that we could take the listening experience to a new level. That takes a lot of effort, determination, investment and courage. It takes an understanding that all this equipment sounds this way because of the technology that is being used and if we want to sound better, then we have to forget about that technology and find something better. And when we find something better, we have to prove that it improves the sound quality. If it does, how do we then incorporate it into a user-friendly domestic turntable design? This thinking is the breeding ground for innovation and is at the core of all Döhmann designs.
The possibilities for innovation are almost endless. Technological development is always offering new opportunities for innovative design. We are constantly researching new breakthroughs in unrelated disciplines, in contact with a network of researchers around the world, attending science and engineering events globally with a view to incorporating new technology in the pursuit of better sound.
There is no doubt that technology is paramount when pursuing high performance. The laws of physics have to be respected and when investigating which designs & materials work best, there is no substitute for research & technology.
However, we are human beings and our engagement with music is emotional in nature. In order to create a truly satisfying musical playback system, you need to have a deeper understanding of psychoacoustics (how our brains perceive music and sounds). To build a turntable which raises the level of musical enjoyment requires an understanding of which design elements influence critical psychoacoustic experiences.
A violin built by a robot may have perfect symmetry & construction. It may be ‘theoretically perfect’ but it simply won’t sound as musically engaging as a violin built by an experienced master luthier.
There are other elements in a design which influence the sonic attributes of the final result. These understandings come through “blood, sweat and tears” and a lifetime pursuit of music playback perfection.
Anyone who has investigated the mechanics of record playback can appreciate the significant challenges that have to be overcome to achieve high sound quality. If it to succeed in connecting you emotionally to the musical experience, a turntable and tonearm must address all of the issues that affect ultimate performance. This involves mitigating microscopic vibrations – a task that requires the ultimate in intelligent design, engineering precision and a comprehensive application of available technology.
In an analogue system, vibrations emanate from the motor, bearing, stylus and drive system. These structure-born vibrations have the most negative affect on analogue playback equipment. They create various colorations and distortions that blur or veil the music, confuse the image and generally wreak sonic havoc.
Sound within the room causes vibrations which hit the turntable, arm and cartridge and cause resonances in the complete analogue system. The resonances move through the system, sometimes reflecting back from some components and creating areas of peak resonance. These vibrations induce various distortions in the signal and their effects are very audible, causing a masking or veiling of the music to occur.
An analogue system is usually connected to the ground so is susceptible to vibrations that travel through the building, through the floor and mix with the mechanical structure of the turntable. Whether its people walking past the turntable or heavy traffic outside, ground-borne vibrations are damaging to the sound quality.
Wow and Flutter
The stability of the rotational speed of the platter is specified as Wow and Flutter. ‘Wow’ refers to slow variations and ‘Flutter’ refers to fast variations in speed. These are measured as a percentage of an average or weighted value. Good performance for a belt drive design is less than 0.1% and 0.05% for a direct drive design. The design and specification of the motor is paramount to dealing with these artefacts. Poorly designed direct drive systems are more prone to have higher flutter. This can be audible as a shimmering to the sound, most noticeable in piano recordings. A good additional measurement for direct drive systems is a peak wow and flutter measurement. This can reveal the sonically audible variations that don’t show in the average measurement. High Peak Flutter levels cause a smearing of high frequency detail.
Speed accuracy is often specified as a percentage and Broadcast standard accuracy is 0.3% or better. Only a 3.3% change in speed will alter pitch one half step. A 6% change is a full sharp or flat.
Speed Drift (Due to Drive System)
Some turntables (especially DC belt drive types) will drift several percent over the 20 minutes of an LP side.
Speed Drift (Due to Static Stylus Drag)
In a freely rotating system like a turntable, any friction near the outside edge will try to slow the rotational speed. In drive systems without servo control, the turntable truly slows down the moment the stylus enters the groove, some as much as several percent. As the stylus moves towards the center or towards end of the record, the torque increases and the turntable regains most of its free rotating speed. To avoid the effects of static stylus drag, the drive system must have servo control.
Speed Drift (Due to Dynamic Stylus Drag)
When the stylus encounters a highly modulated groove, it must do extra work in the groove. During this time, friction and drag increases on the drive system and an effect is experienced similar to discharging an electrical capacitor. Based on the duration of the loud passage of music, and the weight of the spinning platter, there is a time constant that determines how quickly the platter slows down. If the platter is insufficiently heavy, the speed can slow sufficiently such that, a moment after the loud passage is over, you become subtly aware of the turntable speeding back up.
There are a host of electrical phenomena that can seriously degrade the performance of an analogue system, including unwanted AC/DC conversion ripple currents & other power supply related currents, various eddy currents, earth circuit currents, magnetic fields, air-borne RFI, etc. The electrical signal created by the cartridge is very small and highly susceptible to electrical interferences.
How have analogue designers dealt with these challenges in the past?
Through the years, each generation of turntable and tonearm designers have tackled the challenges inherent in the mechanism with greater or lesser degrees of success. Typically, there are no ‘perfect’ solutions and lots of compromise because often a remedy for one problem often introduces a host of new problems.
However, in time designs evolve as our collective understanding improves. Coupled with advanced engineering techniques and access to better materials and manufacturing methods, the sound quality of vinyl reply has been steadily improving with each generation.
Of note are the legendary EMT tables of the 1950’s and 60’s, the Thorens of the 60’s and 70’s, the Sota and Oracle tables of the 80’s and Rockport Sirius III tables of the 2000’s, just to name a few.
The analogue replay mechanism has undergone waves of development where schools of thought have created epoch-making designs. These designs have constantly shifted the sphere of influence from Europe and the UK to USA and Japan. Schools include Idler drive, belt drive, suspended vs non-suspended, solid mounted, direct drives, vacuum, ring clamp, pivoted, linear and hybrid combinations and numerous other cyclic trends, which remain instantly recognisable.
From budget entry-level to cost no object designs, the huge variety in turntables and tonearm design shows no sign of abatement. However, we believe that only a handful of designers are actually breaking new ground and making progress. This is the space that serious audiophiles observe closely as the ‘bling’ is soon differentiated from real innovation.
In our opinion, technological insights need to be balanced with an understanding of psychoacoustics (how our brain perceives music and sound) which is borne from a combination of engineering design experience and thousands of hours of making a design change, then listening to the result.
Our constant drive to improve on the current state of the art is based on the understanding that the design journey encounters new opportunities for breakthroughs in music reproduction often from outside the world of hi-fi. Sometimes the best ideas come from unexpected places!
We need to have an open mind to explore new sources of inspiration based on an accurate understanding of the underlying challenges in trying to extract an electrical signal from a mechanical device. For example, isolating a turntable from ground transmitted vibration has always been a challenge for turntable designers and a variety of solutions have been used, including suspension systems based on springs, rubber, plastic, foam, air, spikes, etc.
We looked outside the audio world and consulted with Dr David Platus from MinusK Technology USA who developed a revolutionary Negative Stiffness Mechanism (NSM) for electron and atomic force microscopy and other applications that are very sensitive to resonance.
Negative-Stiffness Vibration Isolators – How They Work
Vertical-motion isolation is provided by a stiff spring that supports the load of the Helix plinth and platter mechanism, combined with a negative–stiffness mechanism (NSM). The net vertical stiffness is made very low without affecting the static load-supporting capability of the spring.
Beam-columns connected in series with the vertical-motion isolator provide horizontal-motion isolation. The horizontal stiffness of the beam-columns is reduced by the “beam-column” effect. (A beam-column behaves as a spring combined with an NSM.) The result is a compact passive isolator capable of very low vertical and horizontal natural frequencies and very high internal structural frequencies.
Minus K® isolators typically use three isolators stacked in series: a tilt-motion isolator on top of a horizontal-motion isolator on top of a vertical-motion isolator. A vertical-motion isolator is shown in Figure 1.
It uses a conventional spring connected to an NSM consisting of two flexures connected at their inner ends to the spring and supported at their outer ends, and loaded in compression by forces P.
The spring is compressed by weight W to the operating position of the isolator, as shown in Figure 1. The stiffness of the isolator is K=KS-KN where KS is the spring stiffness and KN is the magnitude of a negative stiffness which is a function of the design of the flexures and the load P. The isolator stiffness can be made to approach zero while the spring supports the weight W.
A horizontal-motion isolation system consisting of two beam-column isolators is shown in Figure 2.
Each isolator behaves like two fixed-free beam columns loaded axially by a weight load W. Without the weight load the beam-columns have horizontal stiffness KS.
With the weight load the lateral bending stiffness is reduced by the “beam-column” effect. This behaviour is equivalent to a horizontal spring combined with an NSM so that the horizontal stiffness is K=KS-KN, and KN is the magnitude of the beam-column effect. Horizontal stiffness can be made to approach zero by loading the beam-columns to approach their critical buckling load.
Figure 3 shows a schematic of a negative-stiffness vibration isolator incorporating the isolators of Figures 1 and 2. A tilt pad serves as the tilt-motion isolator. A vertical stiffness adjustment screw is used to adjust the compression force on the negative-stiffness flexures thereby changing the vertical stiffness.
A vertical load adjustment screw is used to adjust for varying weight loads by raising or lowering the base of the support spring to keep the flexures in their straight, unbent operating position. This feature can be automated in single-isolator systems and to achieve automatic levelling in multiple-isolator systems.
Ultimate Vibration Mitigation System Without the Need for Air or Electricity!
Our research showed that the MinusK NSM technology was a far superior solution for a turntable’s requirement for six degrees of freedom ultra-low natural frequency vibration isolation.
Integrating the MinusK NSM into a turntable design produces the best resonance isolation solution ever experienced on a turntable. Virtually all top end designs are using suspension systems based on refined applications of air, rubber, springs, plastic, foam, air or spikes. When compared with the vibration mitigation performance of NSM, these solutions are vastly inferior. Another benefit is that neither air or electricity were required, eliminating the complexity and inherent issues that were associated with those design solutions.
Designing the turntable chassis simultaneously with the MinusK technology allowed us to accurately determine the “crossover” points where the MinusK low-frequency isolation needed to interface with the mid and higher frequency damping and control systems. This complete mechanical integration resulted in superior performance to simply placing a MinusK platform under a non-optimised turntable.
Micro Signal Architecture (MSA)©
Micro Signal Architecture© (MSA) is a cohesive design approach that uses the most advanced available techniques to remove physical vibration, mechanical vibration and electrical noise.
The application where the greatest research on micro-vibration mitigation has been conducted is the world of electron & atomic microscopy. Images at the nanoscale are extremely sensitive to external vibration, even under vacuum. Experiments utilizing sensitive equipment such as; Atomic Force Microscopes, Electron Microscopes and laser scanning systems, require the staff to stand still in the building and machinery to be disabled, when a sensitive image is captured by the microscope.
In actuality, even foot-steps several floors above can transmit through concrete structures and blur the images. Only with the installation of advanced vibration suppression and isolation can the images be retrieved in fine enough detail to show new insights. So how analogous is this to audio?
For analogue systems such as the audiophile turntable it is extremely relevant to the performance of the table. For vinyl playback, the enemy of any signal found in the mechanical groove by stylus tracing is also vibration and electrical interference!
Many audiophiles and music lovers lament the effectiveness or lack of isolation on turntables, even in cost-no-object designs. Our research has found that existing turntable suspension and isolation systems may not achieve the real-world performance objectives they claim and listeners often experience distortion, feedback, information blurring and over-weighted boomy bass response.
Modern homes are not designed for vibration control. In older homes with wooden floors these systems become unstable and do not stop footfall or feedback loops occurring (the classic tiptoe around the suspended turntable else your cartridge mis-tracks syndrome). This is predominantly due to the natural frequency of these suspension systems not being low enough (0.3hz-1.5hz).
The innovation in the Helix turntables relate to the ingenious way the NSM isolation technology is integrated. The turntable and NSM device form a fully acoustic and mechanically balanced system. The result is a precisely designed “mechanical crossover” that harmonizes the forces at play between the incoming external acoustic and mechanical vibrations and the self-generated internal vibrations caused by bearings, motor and chassis dynamics.
By using the latest software measurement technology for Chladni plate analysis and engineering ‘cymatics’, the team at Döhmann Audio has developed a complex chassis system that effectively damps vibration utilizing a semi-active topology.
Döhmann Audio extends this MSA thinking to the unique arm board damping technology that has been used in every Döhmann designed turntable since the late 1980’s. This technology extends the performance of an already world-class design to levels not achievable by other means.
TDS (Pre-Stress Accumulation and Release)
One of the major influences in the sound reproduction of vinyl play back is mechanical vibration. After all, turntables are mechanical devices. What if a “mechanical crossover” concept could be extended to create a smooth continuous pathway to channel vibrations away from critical areas on a turntable?
The Helix One and Two platforms use our proprietary TDS solution which forms a semi-active damping system to further lower the noise floor of the overall system. This technology uses a pre-stress accumulation release (PAR) strategy to mitigate vibrations inside the chassis caused by motor bearing and platter bearing noise. This technology creates a path of least resistance for these vibrations, channels them away from the critical signal path zones and dissipates the energy.
The primary source for energy dissipation is the material damping of higher frequency vibrations. Whilst frictional dissipation contributes to the system balance using constrained layer plates each plate has been designed using the latest Finite Element Analysis (FEA) and Finite Element Modelling (FEM) methods in advanced software (COMSOL).
Energy dissipation contributions at the time instant of node activation, amount to around 80% for material damping and 20% for frictional dissipation. There is additional dissipation not associated with any physical process (derived using Hilber-Hughes-Taylor calculations of motion).
Effective mitigation of such vibration further extends the performance of any tonearm mounted on the armboard. This semi active magnetic technology attenuates the last vestiges of noise generated by vibrating structures. The system does not require power or any servo feedback and has a larger restoring force than the physical drag caused by a stylus in the groove.
This geometrically locks the system into the chassis whilst it isolates the armboard from motor and bearing noise. This innovation was pioneered in the earliest Döhmann turntable designs first seen commercially in 1985 and has been thoroughly refined in the latest Helix chassis designs. The system is in effect an adaptive shock-absorber and control for energy dissipation in a flexible floating plate structure.
Pre-Stress Accumulation Release
The turntable is equipped with a device that constrains the relative slip between layers of plates. The strain accumulated in the structure locally is released as it occurs which results in conversion of a part of the strain energy to the kinetic energy of local, higher frequency vibrations. These higher frequency vibrations are then sunk into heavy damping materials which absorb and convert these to heat.
The equilibrium is restored rapidly to allow the structure to return to the initial state by means of a gradual release of the pre-stress accompanied by the frictional dissipation in the contact surfaces. This architecture is used as a Mechanical Crossover to selectively reduce each band of frequencies.
The MinusK NSM system absorbs and isolates low frequency vibrations up to 100Hz and the Mechanical Crossover then uses the complete constrained layer plates to absorb mid-band vibrations. Higher frequency artefacts are then focussed and dissipated in the PAR system.
From this method we learn the shape and weight of the components influence acoustic behaviour under vibration. Therefore, selection of materials and the suspension elements used determines the crossover frequency and effectiveness!
By extending the mechanical crossover concept to the Helix platforms, physical zones can be defined on the infrastructure that focused vibrations away from key areas (platter, bearing, motor, tonearms, floor modes), establishing a smooth continuous pathway to channel vibrations away from critical areas on the turntable.
The Helix platforms have been designed to reject low frequency vibrations coming up from the floor by using the MinusK NSM isolation system and drive higher order vibrations generated through motor noise away from the bearing and platter via a complex coupling to the chassis. For these higher order vibrations local isolation, absorbing, redirecting and suppression technologies are employed including semi-active decoupling from motor vibration.
Helix turntables have designed to operate flawlessly in non-ideal environments suffering from floor borne vibrations such as older houses with wooden floors, upper floors, attics and any external vibrations which are carried through buildings – even those made from concrete steel, and brick.
Measurement and Visualisation Techniques are used which enable the Döhmann engineering team to ‘see’ these vibrations in real life, especially how they move and where they ‘collect’ on a chassis under real life operating conditions.
HTAD (High Torque Adjustable Drive)
The precision motor industry is changing rapidly to embracing a software driven architecture. Helix technology is taken from the latest developments in sub-micron servo drive systems for precision optics and adapted by our engineering team to deliver superior motion control to the Helix turntables.
The Helix motor control system is a digital closed loop servo with greater than 16bit resolution. Absolute positioning reading occurs over 120,000 discrete positions of the rotor per revolution. The motor spins several hundred times to achieve one revolution of the platter thus increasing the system resolution by an order of magnitude over a direct drive topology.
In layman’s terms, this means at 33/45 rpm platter speeds we have an incredibly high number of checks on the speed stability per second. This information is fed to a very fast microprocessor in the servo control and our custom written software then defines the stiffness and the ballistics of the system and responsiveness of the servo loop. Different inertia/force ratios can be programmed to yield different sonic signatures and sound dynamics.
The table can act like a high torque direct drive or like an underpowered low torque design depending on servo programming. Torque force can be adjusted to suit sonic palettes and the frequency of the drive shifted to areas that are better handled by the mechanical design and vibration control.
Cogging is prevented by a proprietary coil design that smooths the motor to vanishing low levels of vibration. Our motor design team has delivered extremely low motor noise on the Helix platform. We have not found any comparable system able to attain similar results.
The speed is factory set for 33 and 45 and does not need adjustment in normal operation. However, if a user wishes to adjust the reference speed a software application via a computer allows adjustment. It is also able to be securely connected to our service technicians for diagnostics and firmware / software upgrades.
The 120mm (4 inch) plinth is made from precision CNC aircraft grade aluminium and structural alloys and weighs close to 50 kg (111 Lbs) when assembled. It is connected by a series of interlocking plates which are fitted closely to the MinusK suspension system and allow for the mounting of the sub-systems such as the motor, bearing and the tonearm combinations. A laminated glass plate is used to add ballast and lower the center-of-mass. This glass plate provides visual access to the MinusK suspension for performance monitoring.
The platter is a four layer design and is the result of many years of research. The Mat is a special elastomer with a fibre reinforcement chosen for its damping properties and ability to protect the LP surface under clamping pressure. The upper platter is a moulded composite sandwich made of a 5000 series aluminium alloy base plate and a 10mm thick composite resin matrix with acoustic refraction properties that resemble vinyl. This is bonded to a 5000 series base alloy composition that includes magnesium, manganese, titanium with Silicon Carbide. This composition was chosen for its high damping coefficient.
The platter incorporates an air gap between the upper and lower platter and weighs 15kg (33lbs). The lower platter is constructed with an Aluminium alloy outer shell with a metal matrix composite system inside. This provides the unique properties of increased mechanical strength as well as beneficial vibration characteristics. The hybrid design uses the Aluminum 5083 as the base metal and the Silicon Carbide and other compounds as the reinforcement material. The composition of each of the reinforcement materials plays a particular part in affecting the damping characteristics or mechanical strength. During development, the results of vibration tests carried out on this hybrid Aluminium metal matrix composite plate as well as the results obtained from computational analysis using software were interpreted to effectively determine the damping ratio, frequency, magnitude, phase angle and ultimately the dynamic behaviour of the composite materials used in this appliction.
Helix turntables use an Edge Damping Ring which damps the platter and LP edge and a damping mat to interface with the LP. The Spindle/Spindle Housing is engineered for high reliability and ultra-low noise operation. Specially sourced Maraging Steel is used to provide the desired precision and low thermal & flex characteristics. Located at the bottom of the spindle, a ceramic ball is used for trouble-free operation on a quiet thrust pad. The high-tech lubrication system is sourced from the aeronautical engineering field to ensure low noise operation.
The Record Clamp
The record clamp is designed for ease of operation and secures the LP effectively on the platter surface and flattens even severe warps in poor quality LP’s.
The clamp is a multi-piece design which has a reduced damage profile in the event a user accidentally drops the clamp onto an LP during operation.
The Motor & Belts
A Swiss-manufactured precision single spindle high-torque motor featuring zero cogging is used. The motor can supply up to 100 watts of power for the most demanding control needs. By using sophisticated control software, the belt system is gently started and bought to rest to avoid premature wear. Speeds are factory set and highly accurate. The Helix One series has a speed adjustment feature located on the PowerBase for final in-room tweaking. This is used to counter the real-world speed variations caused by temperature, humidity, lubrication variables, etc.
Dual high damping o-ring belts are provided for stable drive transmission. The use of two belts is a Döhmann Audio innovation.
The Helix One supplies two armboards (for dual arms) that are removable and can be pre-drilled for most commercially available arms or left blank for future use and the Helix Two supplies one armboard facility. The armboards are able to be fitted or removed externally with arms mounted. No need to dismantle and recalibrate. The chassis has a damped tubular cross-section underneath which precisely locates the armboards relative to the bearing and platter. This provides a very rigid system with minimal flex and movement.