‘Leoht’ – derived from the old English word for ‘light’. In this case not of the optical kind but an object with significantly reduced mass. Mass absorbs energy and the reduction of mass therefore allows unwanted energy to dissipate more efficiently. One definition of light is ‘radiant energy’ or ‘that which makes things visible’. The faster unwanted energy can dissipate, the more accurate the measurement of vibration from the record groove will be. Introducing Project Leoht.
Leoht has been 3 years in the making. I started developing Leoht in the second COVID lockdown. I underestimated how complex the project would be, and there came a time where the challenge seemed too great and the project was temporarily shelved. Leoht is a culmination of everything I have learned through many years of research, trial, error and success in turntable design and the teachings of my engineering influences. I have been involved in the high-end audio industry for more than 10 of my 28 years on this planet, and I’ve been into hi-fi as an enthusiast, and vinyl for double that. I have analysed, questioned, validated and disproven many of the commonly held beliefs in high-end audio. I have heard, repaired and built countless pieces of audio equipment including building several turntables, broadly representing almost every known approach to the design of a record player.
I have learned a lot along the way. There are very few real engineers in high-end audio. Many products, especially those commanding astronomical sums of money, are built on at best a limited understanding of physics and the sciences of sound and materials. More commonly products are built with a total lack of engineering at all, instead throwing materials together to meet a cost and form a machine best described as ‘functional’. At worst, products in the audio industry which are fraudulent are the norm and by no means the exception, designed to fleece the clientele with limited technical knowledge but plentiful finances, who represent the majority of the group defined as ‘audiophiles’. Most ‘experts’ in the hi-fi industry are not experts at all, the majority of writers in the consumer audio press don’t have a clue what they’re talking about, too many retailers pedal their own biases or high-margin items, misinformation is perpetuated across countless online fora and press advertising budgets rule.
Leoht is based heavily on the engineering principles of Rega Research, headed up by CEO Philip Freeman and co-founder Roy Gandy, engineers for whom I have great respect. Rega’s low-mass, high-rigidity principle is unique in the industry, founded on knowledge accumulated in material science and physics. Rega’s turntables have been on the market for over 40 years. But the development of their Naiad testbed after the unexpected vinyl resurgence in 2009, and thereafter revisions to production products starting in 2012 broke serious ground in what the company was able to achieve; thanks to lightweight Polyolefin and Polyurethane foam core plinths and advancements in CAD and manufacturing technology. Notoriety helps too, as it brings financial gains and opens doors to work with other firms in the fields of formula 1 and aerospace manufacturing and other industries led by advanced material science.
Their philosophy is one of a ‘vibration measuring machine’ where the record player is a mechanical tool to ‘measure’ the vibrations enacted on a stylus as it traces the groove of a rotating record. Records themselves are inert, and only by rotating them and bringing a stylus of microscopic dimensions into contact with the bumps and ridges formed in the groove wall can a vibration be ‘measured’. The length of a ridge depends on its frequency and the height on its amplitude. Towards the centre of an LP, a 10kHz signal is roughly 26 microns long and may be less than 10 microns high if it is a quiet signal.
The chassis of an ‘ideal’ turntable is one where mass is reduced as much as possible while stiffness is maximised, with a compromise reached between the two depending on the materials available and the cost of the product if production is the ultimate goal. Accuracy is key, with components machined to microscopic tolerances that push the limits of the materials used and in many cases exceed what is achievable with current production techniques, necessitating the development of new methods of manufacturing to achieve components that meet the desired tolerances. Most of those tolerances measured in micrometers, a thousandth of a millimetre or one thirtieth of the diameter of the average human hair.
The turntable should be considered and developed holistically, not as individualised components that are later assembled to form a ‘functional’ unit. Every component in the turntable influences every other component. Nothing in engineering is perfect. There is no such thing as perfect, there are only acceptable compromises that are as close as is practically achievable to an ‘ideal’. Only by designing holistically can we achieve an end result that balances those compromises and build an accurate ‘vibration measuring machine’, but one that is musically satisfying when it is used for its intended purpose, reproducing music from a vinyl record.
Recounting every engineering and scientific area of turntable design as understood by Rega is beyond the scope of the article but fortunately they have already done so in a book entitled ‘A Vibration Measuring Machine‘, by all accounts a detailed and candid exploration of their more than 40 years of research. I have yet to read the book myself as, following audio company form, they are behind the times and haven’t released it in a digital format, and I can’t read a paperback.
The Plinth
The plinth is the chassis onto which every component of the turntable is mounted. It forms the supporting structure for the drive system and pickup arm and should be as light as is practical yet as stiff as possible. A key aspect in the design of any turntable in the relation of the pivot point of the arm to the centre point of the record, which is critical to the alignment of the stylus to the groove and the reduction in tangential offset error as the arm traces the record in an arc. The pivot to spindle distance must remain absolutely consistent, and thus rigidity of the plinth in this area of the utmost importance.
The shape of the plinth is optimised to remove as much material as possible to reduce its mass, but to also control resonances within the plinth that may be excited by vibrations born from the bearing, motor and arm as well as airborne environmental vibrations. The turntable has 6 key mounting locations for the feet, arm, hub bearing and motor. Plotting these points and maintaining critical distances where necessary gives us a rough outline of the plinth shape. The centre of gravity will be focused around the platter, as it is the heaviest component and a rotating balanced mass, and this dictates the locations of the feet. Too far apart and the plinth is excessively large and the thin sections of supporting material too fragile. Too close together and the turntable may be physically unstable and the optimal mechanical coupling between the turntable and its supporting surface could be compromised.
Material can then be added or removed as required to add strength, reduce mass and improve aesthetics, though the latter is a secondary consideration here as the best possible performance was the ultimate goal. I went through four prototypes before arriving at the turntable you see here, Leoht version 1.0.
When Lehot development started the best production turntable based on these concept was the Rega Planar 10. It uses a Tancast 8 foam core sandwiched between skins of HPL laminate. Tancast 8 is a closed-cell rigid polyurethane foam with a density of 120KG/M2. Rega’s nominal plinth thickness is 19.6 mm, so I estimated that each laminate was 0.8 mm and the foam core 18 mm. During the time this project spent on the back burner, Rega released the Naia turntable. It too uses a Tancast 8 foam core but with graphene-impregnated carbon fibre skins.
My first two prototypes used Tancast 8, bonded to HPL using CTA1261 polyurethane adhesive. The combination worked well but I naively hadn’t checked the thickness tolerance of the foam that I was sent. I discovered that the batch I received had been incorrectly cut, and was unfortunately unable to amicably rectify the issue with the UK manufacturer. Further digging and conversations with engineers who had experimented with foam sandwich panels showed the tolerances achievable with Tancast were less than I was aiming for. I’ve no idea what the thickness and surface tolerances are for the Tannest sheets in Rega’s P10 and Naia, but I’d imagine a lot of complex but gentle machining and a challenging glue-up is involved.
I switched instead to Rohacell, a foam based on PMI (polymethacrylimide) chemistry. I used the 110IGF variant, which has a density of 110KG/M2 and is the same grade of Rohacell used in Rega’s Nayad testbed turntable. Rohacell can withstand 435 PSI (30.58 KG per square centimetre) of compression and is incredibly strong, when used as a core material in a sandwich panel.
The first four prototypes used a standard matte black 0.8 mm thick HPL. This appeared to work well initially, but ultimately didn’t offer satisfactory stiffness when combined with the Rohacell. I noticed as I was assembling the third prototype into a functional turntable that the plinth had twisted and was unstable enough that adjusting the feet could flex the plinth while it held only the weight of the subplatter, arm and motor.
Prototypes three and four had other faults too including a leaning bearing and lack of stiffness in the brace, causing the platter to lean to one side, and the arm to lean in the opposite direction. I had seen reports of Rega’s Tancast-based turntable’s sagging, most notably the P6 in which the sag is more obvious due to its traditional dust cover design, but had always assumed the cause was the foam and / or the adhesive and not the HPL laminate. They use different bracing materials so it’s not an ‘apples to apples’ comparison, but I wonder what could be done to stiffen the HPL sandwich panels to eliminate sag without compromising too much on weight. A resin-based adhesive, or edge banding perhaps.
Leoht instead uses a quasi-isotropic carbon fibre layup with 0°/90° and 45°/-45° fibre orientation. This layup technique offers improved stiffness across the diagonal axis of the panel and significantly improved torsional stiffness. The laminates are sheets with fibre type, weight and weave symmetrical from the front to the back ply to maximise stability and flatness with a maximum thickness tolerance between sheets of ±0.2mm.
The plinth and all adhered components are bonded with Permabond ET538, which is a slow-curing two-part structural Epoxy resin adhesive. Laminating a closed-cell foam is not as easy as it sounds. The adhesive has to fill the tiny pockets between the cells, but must be compressed sufficiently to produce a perfectly flat sandwich panel without excessively stressing the foam core. Excessive adhesive can be absorbed into the foam to a degree, but will only add unwanted mass and structural damping. You also have to figure out a means of closing, and pressing, the panel without trapping air between the skin and the foam surface, creating pockets of air that weaken the bond and can compromise the thickness tolerance of the finished panel.
Bracing
Additional bracing is used to greatly increase stiffness between the platter bearing and the mounting point of the arm to minimise as much as possible microscopic movement between the two. Rega turntables have long featured a double brace running between the tonearm and platter bearings both on the top and bottom of the plinth. Rigidity of the plinth in this area spanning 222 mm centre to centre is critical if the stylus is to follow the groove with the optimal geometry and correct tangential offset.
When a material or structure is ‘excited’ at one of its natural resonant frequencies it vibrates and deforms with an associated characteristic deflection pattern. This is called a ‘mode shape’. By altering the shape of the structure, combining materials and moving components in relation to one another, we can stiffen the problem mode. Thus structural excitation and the resultant deflection are lessened.
Given the critical relationship between the tonearm and bearing, the plinth is optimised to minimise problem modes at likely excitation frequencies. These include airborne vibrations, but also vibrations generated by the moving components of the turntable and any energy that is not dissipated within the structure of the arm, and is therefore transferred into the plinth structure. This is the reason not only for the bracing, but also the shape of the plinth.
The P10 uses a ceramic top brace and a phenolic bottom brace. The Naia uses a pair of ceramic braces. Ceramic is a stiff, hard material perfect for this application. I lack the budget for a one-off ceramic brace, even if I could find a company who would produce one. My first four prototypes used a top brace of quasi-isotropic carbon fibre and a synthetic resin-bonded fabric (SRBF) material, an extremely rigid yet lightweight blend of epoxy resins and cotton fibre.
Leoht uses a pair of carbon fibre braces – one mm on the top and two mm on the bottom. Experimentation led me to look at what might be achieved by bonding layers of carbon fibre sheet to orient the direction of the fibre at various angles. I found that orientating two pieces at an alignment of 28 degrees, bonded under high pressure with an epoxy produced an extremely stiff brace with minimal ringing, and resonant frequencies far from those of the top brace comprised of a single 1 mm quasi-isotropic carbon fibre plate. I decided that the major advantages in stiffness and weight over the SRBF outweighed any disadvantages of using similar materials in the two braces.
Managing Stress
key to the design is the elimination (or at least the minimisation) of mechanical stress in any component. Compression, where bolts securing hardware clamp the plinth, create compressive (squeezing) stress at and around the fixing point. In the first three prototypes, tapped holes were used to maximise mechanical contact and the bolts were glued in place. The first prototypes used nylon bolts and fasteners almost exclusively to further reduce mass with Only the arm secured by steel bolts. These worked but didn’t provide enough rigidity in the motor mount and feet without excessive compression.
Leoht uses through bolts, nuts and standoffs where appropriate to mount the components. They are torqued evenly to1nM and carbon fibre washers are used in critical areas to spread loads with minimal added mass. Mounting components to limit stress is something i intend to revisit in version 2.0.
The feet are 6000-series aluminium, 38 mm in diameter tapering to 10 mm. They are mounted using threaded nylon mounts which allow 10 mm of adjustment to level the turntable. The nylon mounts are glued and bolted to the plinth to the plinth. The design of the feet couples the plinth to the supporting surface rather than isolating it, with 2 mm rubber pads the only isolating material. The feet are machined internally to reduce excess mass and resonance, but there is still some way to go in devising the ultimate low-mass, anti-resonant foot for a turntable like this.
The Bearing
The bearing housing is VHL (Vesconite HiLube) thermopolymer. VHL incorporates an internal lubricant and has an exceptionally low friction coefficient with excellent dimensional stability, and can be accurately machined to micron tolerances. In this application it will withstand millions of hours of use without significant wear and is significantly lighter than a brass bearing sleeve. A ZTA (Zirconium Toughened Alumina) bearing would be superior in hardness and stiffness, but it is not a viable material for one-off projects. VHL should be at least equivalent in noise performance and mechanical wear is not a realistic limitation in this application, though ZTA does have an advantage in hardness.
One of Rega’s most recent advancements is involves a change in the way the bearing is fastened to the plinth. Traditionally a nut secured the 18 mm threaded bearing housing from beneath, but this creates a point of compressive stress and doesn’t give the best interface between the plinth and bearing housing. Current designs have an aluminium boss screwed (and bonded) into the plinth with a custom-designed locking thread. In prototype three I forwent this altogether and bonded the VHL bearing sleeve straight into the plinth with epoxy. This was a mistake as the epoxy forced the bearing to lean slightly, even though it appeared even from the top. Fortunately epoxy doesn’t stick well to most polymer plastics, so a sharp tap from a mallet freed the bearing leaving no glue behind.
In Leoht I simply made the bearing housing an interference fit. I used a nut beneath to secure the bearing, adjusted to minimise mechanical stress as much as possible, with a carbon fibre washer to spread the load bonded with a dab of CA glue.
The Platter
The platter is machined from Delrin, a POM (Polyoxymethylene) engineering plastic. The platter weighs 1.71KG and is machined to focus the majority of its mass around the periphery, thus creating a flywheel to aid speed stability. Multi-layered glass was considered as an alternative, as was ceramic but neither is realistically an option for a one-off build. Delrin is an excellent platter material as it is immune to static, uniform in density and can be accurately machined to a perfectly flat surface. It is lighter than I would like, however, and I think the flywheel effect could be vastly improved. I have a few other platter materials in mind that I will experiment with for Leoht 2.0.
The subplatter or ‘hub’ on which the main platter rides is machined from 6061-T6 Aluminium with a 316L low-carbon stainless steel spindle. The hardened spindle runs on a polished Zirconia ball bearing. The hub itself was balanced to minimise runout and limit its impact on the platter flywheel. It’s also important that the platter be perfectly centred on the hub with the least runout possible. The platter was machined around the centre hole, which was machined to be a close-tolerance fit to the hub.
The spindle is precisely dimensioned to place the thrust point of the bearing at the optimal distance from the centre of gravity of the rotating platter, which behaves gyroscopically. a spinning flywheel with its centre of gravity close to the thrust point (the point of contact where the end of the spindle meets the bearing) is inherently unstable. So much so that without constraint, it will upend itself and spin in a more stable manner on a thrust point that is further away from its centre of gravity. In many designs the relation between the thrust point and the platter centre of gravity is not considered, and the effect is higher sideways forces acting upon the spindle and the bearing housing resulting in noise, wear, runout, and unstable speed.
The bearing sleeve is machined to extremely high tolerances; measurements are within a few microns. Only a couple of drops of the oil, a film thickness of a fraction of a micron, is all that is required. The result is a smooth and quiet bearing, with optimal centre of gravity for the flywheel-effect platter. Thin EPDM (Ethylene Propylene Diene Monomers) synthetic polymer rings are set into the hub and in machined grooves around the spindle centre to grip the platter. THeir elasticity is carefully balanced to not provide excessive damping yet not allow the platter to move. Physical points of contact are preferable when the platter is produced in a ceramic or glass, but a plastic platter is susceptible to thermal expansion and contraction so a slightly flexible point of contact and a flexible interface to ensure concentricity with the hub are desirable.
Motor & Power
The motor is a 24V Premotec 9904 111 31823. This is the typical 24V AC synchronous turntable motor as used by many manufacturers. They are basically modified 7.5-degree stepper motors, adapted to run smoothly when driven an synchronously with an AC voltage of specified frequency. It is driven by an adjustable anti-vibration circuit and an outboard power supply which provides synthesised 50Hz and 67.5Hz waveforms for 33.3RPM and 45RPM speeds respectively.
At the moment the PSU is a modified Rega Neo. The Neo uses an AD9837 28 bit DDS (direct digital synthesis) waveform generator with a 4mHz 100PPM clock source, an odd choice as the frequency step of 0.0149011612Hz does not allow the speed to be set exactly to 50 / 67.5 or 60 / 81Hz for 33 / 45RPM speeds. A 4.194304mHz clock source gives you a frequency step of 0.015625Hz, and allows exact 50Hz and 60Hz (plus the respective 67.5Hz and 81Hz) settings to be achieved. A bit of diligent web searching will turn up schematics for the Neo which are useful in making modifications and adjustments.
I plan to build a PSU with dual DDS generators, software-configurable output and phase angle and perhaps other features in due course. I’d like to experiment with the 12V variant of this motor which should reduce motor noise (which is already negligible) even further. However with the anti-vibration circuit and even a stock Neo, it is possible to reduce the motor vibration to a point where it is difficult to feel (at 45RPM at least) so it is not a priority for me. The modified Neo brought me closer still, though my particular power supply seems to cause the motor to exhibit a great deal more vibration at 50Hz regardless of the adjustment.
The motor itself is modified with new high-tolerance bushings supporting the shaft top and bottom and an adjustable thrust bearing. Most of these motors either have a fixed thrust bearing, comprising a small spring-loaded thrust pad in a plastic housing, or have no thrust bearing at all. The adjustable thrust bearing allows the end of the shaft (which is additionally polished to reduce friction) to ride on a polished stainless ball bearing inside an aluminium housing. The height of the bearing is set by a grub screw, allowing the shaft to be adjusted up or down to optimise the alignment of the rotor and coils, reducing vibration even further and eliminating bearing noise.
The motor mount is machined in acrylic and holds the motor from underneath. The motor is glued in using a 3M foam pad that is designed to offer a permanent bond but is still flexible enough to allow a tiny bit of rotational movement. The motor mounting plate is carefully machined with a rebate to prevent the motor shifting in any direction, but to provide an exact close-tolerance fit to the motor to minimise mechanical stress. The motor is secured using M3 bolts through the plinth arranged in an equilateral triangle.
Belts
The three belts are clear silicone rubber in its purest form with no additives. These are produced in a custom tool which produces a continue belt without a join, and one that is perfectly round and uniform in thickness throughout. I had to produce a custom tool for this and was fortunate enough to happen across a toolmaker with the expertise and understanding to achieve what I wanted, and due to the COVID pandemic some unexpected free time to assist. The best commercial o rings I could buy weren’t even close to the tolerances I wanted, and many of the aftermarket belts manufactured for these turntables are worst still.
The tool comprises a pair of turned circular plates with a tapered pin machined onto one and a respective hole in the other to join them with perfect concentricity to press the belts. The grooves in the plate surfaces that form the belts are machined around the tapered pin and its receiving hole so that the adjoined halves of the cured belt are also perfectly concentric. Only one belt can be pressed at a time, and achieving the desired elasticity took a lot of trial and error. The quality and consistency of the belt can profoundly affect speed stability as well as torque. They drive the hub via a machined brass pulley with a butyl rubber insert at the bottom to provide perfect concentric alignment with the motor shaft. Currently a dab of silicone secures the pulley, but in Leoht 2.0 I will experiment with the idea of freezing the pulley to the motor shaft which should virtually eliminate runout.
The Arm
The arm started life as a Rega RB202 that I bought for a fraction of its value as the original owner had attempted to re-wire it, ruining the bearings and the original wire. All that was retained were the base and the single-piece tapered arm tube. This arm tube is a commendable piece of design that would be considered by many to be impossible to cast, and came to fruition only through Gandy’s perseverance, like-minded engineers and advanced 3D modelling.
In order for the cartridge to accurately measure the vibrations caused by the movement of the stylus within the record groove, the cartridge must be kept absolutely still in the headshell. The cast alloy arm tube is gently tapered along its length which greatly increases stiffness and optimises mass distribution. Furthermore conical shapes dissipate resonance, directing unwanted energy away from the cartridge.
I chose ABEC 7 bearings which were measured and hand selected by the supplier for an inside bore and outer tolerance of less than 3 microns. They were the best fit we could achieve to the components of this particular arm and no adhesive was used in the assembly. Zero play is absolutely critical in a tonearm but so is free movement. In reality there is a little over a micron of preload. Bearing friction is better than I can measure – less than 10 milligrams. The arm is wired with a hair-thin flexible internal cable specifically designed for tonearm wiring and a highly screened, low capacitance external cable by Van Damme with discrete ground.
It is finished with a stainless steel counterweight and counterweight stub. It does not, unfortunately, have the facility for constant downforce compensation and is entirely static balanced, which I consider its main disadvantage. The glass-loaded plastic base is not ideal either. I wouldn’t mind stripping the black paint and mirror polishing the tube to reduce arm tube mass, and a stiffening brace at the point where the headshell meets the arm tube wouldn’t hurt. This is all for Leoht 2.0 and beyond. It’s still a fine arm though and I’m confident it could show many high-end arms costing tens of thousands of pounds the door.
The current cartridge is an Audio-Technica VM540ML with a MicroLine stylus. It is fitted to a newly designed RigB (Rigid Body) from the folks at IPT, designed especially to utilise the three-point fixing holes of a Rega tonearm. Using three fixings in a triangular arrangement greatly increases the coupling between the cartridge and the headshell, and the body itself is machined to accurately fit the generator which is then bonded into place with an Epoxy. The bolts are evenly torqued to 0.4Nm.
Performance
After three years everything had finally fallen into place and I connected it up for a listen. The sound is quite astonishing. I’m genuinely amazed by the level of detail you can get dragging a tiny rock over a spinning plastic disc with bumpy grooves on it. My long-standing point of reference is a Technics SL-1200G, objectively one of the world’s finest turntables in every measurable area. Leoht does a better job of unearthing micro detail in a mix and better portrays dimensionality and spacial information in a mix. The Technics is no slouch in any mechanical area, so I put most of this down to the energy dissipation of the lightweight plinth, its mechanical coupling to the surface (the Technics is largely isolated), and the extreme rigidity between the hub bearing and arm.
I was also pleased to note how stable the speed is. I have perfect pitch which is usually a blessing, but I can’t stand listening to a lot of belt drive turntables because they either have excessive variance (wow & flutter) or they play at the wrong speed. With the modified Neo and the tuned motor, I’m able to achieve an average measured speed of 33.3349 RPM accounting for stylus drag. One measurement hit 33.3333. Wow & flutter are a tad higher than I’d like but any variance is inaudible to my ear.
Leoht weighs less than 4 kilograms fully assembled. The plinth, minus the platter and arm but including the motor, the hub, the bearing and feet and all mounting hardware, is approximately 880 grams. The plinth itself, including the braces, is just 206 grams.
Lessons & Improvements
My intent with this project was originally to build a statement piece, and one that would stand as my last turntable design. I thought I had achieved that and there weren’t plans for a follow-up, but restless minds never stop so Leoht 2.0 is already in the works.
There is a lot of scope to further reduce the size and mass of the plinth, while greatly increasing its stiffness in key areas – the mounting locations for the feet in particular. By my estimates I think I can cut the weight in half and increase rigidity in key areas at least three-fold using the same materials. Speaking of the feet, further mass may be cut, and resonances reduced, through experimentation with carbon-loaded plastics and resins. The mounts need reworking to remove stresses in the plinth and more rigidly couple the feet to the plinth in a way that maintains the ability to adjust the height.
There’s work to do on the drive system. The tolerances in the hub and bearing can be improved, and the mass of the hub reduced. So too can the mounting of the bearing to the plinth, where there is currently an undesirable point of stress. I’ll experiment with freeze-mounting the motor pulley and look to stiffen the motor mount while reducing its size and mass. And there is much to do in perfecting the platter including experiments with platter materials and the underside profile to achieve a better flywheel and find strike the optimal balance between the profile and the platter mass for each material.
I would also like to experiment with motor technology. A small brushless motor driven by PWM could provide sufficient torque to drive a flywheel platter and would be a lot smaller and lighter. It would also be easy to control using a microcontroller and minimal external circuitry. I also plan to experiment further with the synchronous AC motor, both in 24V and 12V variants as there are still advancements to be made in synthesised power supplies. Either way, less vibration is the goal which will result in better performance overall. There is work to do on motor screening too, as radiated interference and cable-induced hum are issues with the current design.
The arm will receive upgrades too as above. A better base, improved counterweight with better concentricity to its shaft, a stiffening brace and dynamic downforce adjustment. I might also experiment with alternative tube designs, and perhaps a gimbal bearing design with static balancing.
I’m working on a device which can measure vibration using a system of highly accurate single-chip gyroscopes and accelerometers. I intend to use it to assess the performance of motors and the energy dissipation in plinths with some objective data. I also came across a system that uses a laser-etched pattern on a glass disc to accurately measure speed and speed deviations, and I’d like to combine that idea with a test tone groove to obtain data from external sensors and the stylus itself to theoretically give a highly accurate representation of what the platter is doing particularly under load.
Finally it would be interesting to track the arm with accurate sensors, perhaps ultrasonically, to accurately record how it, and its various components, behave and how they might be optimised. These are immensely complicated endeavours for a one-man band with limited capital for these projects but I intend to document developments as I move this concept forward. Now that I’ve proved its efficacy, I can envision future designs that will push these ideas to their limits and beyond and I’m excited to see how far I can take Leoht.
The Leoht story
With the details out of the way I’d like to take a few more words to tell a little of how this turntable came to be. In 2020 during the Covid lockdown, I built Project Glacier. Glacier followed an entirely different concept; one of high mass and heavy use of isolation. Project Glacier was a great success though having listened to it for over a year I have become aware of some shortcomings in its performance. Primarily over-damping due to the mass of the plinth and its material, which makes the turntable bass heavy at times, but quite blurred in the low end. The best analogy I can give is one of two vehicles racing along a straight road; one a heavy lumbering lorry and the other a nimble hatchback.
I owned the previous incarnation of Rega’s design, the RP10, some years ago which gave me a taste of what a low-mass turntable could offer sonically, and I was impressed. Unfortunately (or perhaps fortuitously, depending how you look at it) my RP10, and some other Rega components I had, were plagued by several quality control issues and were ultimately returned under warranty. These products cost a lot of money and while things made by humans can and do go wrong, there comes a point where the level of failure outweighs the cost, especially when the products are brand new.
It does seem that Rega have worked hard to perfect their standards of quality control and i read very few reports of issues with newer products of theirs. And it has to be said that their level of service is up there with the best in the industry, even if they hide too much behind a network of dealers. I’ve still yet to hear any of the company’s latest offerings in person despite running a highly successful review publication and trying on several occasions to secure samples and / or demos – Rega simply haven’t been interested. I’m not about to buy one at retail – I work in the industry and I avoid consumer audio retail as a general rule.
I decided that if I couldn’t hear what Rega had to offer, I may as well build my own turntable based on the low-mass principle. The instantiation of a second national lockdown in 2021 left me with some free time on my hands. However, getting the materials together and designing a project like this doesn’t happen in a short space of time, and by the time the first drafts of the designs were completed and the materials began to arrive the design had become my own. Indeed while the inspiration of the P10 is certainly evident in Leoht, the two turntables are actually quite different in their design and build.
The Planar 10 is not an easy product to ‘clone’. The vinyl resurgence and Rega’s considerable success in the field has given them the freedom and the funds to spend a lot of money on R&D. They also have several skilled engineers, some of whom have been working in the field longer than I have been alive, and who are proficient in CAM and CAD and the machinery to bring those computer-drawn models to life. I am not especially proficient in CAD nor do I have deep pockets.
What I did have, however, was determination and a desire to see the project through to completion. I do possess a lot of knowledge concerning the mechanics of vinyl replay, and have had the opportunity to assess many designs conforming to all of the commonly accepted principles. I think I am at least a reasonably competent mechanical engineer. I have a friend who knows his way around a CAD program like the back of his hand. And I have a patient long-suffering father skilled in technical drawing.
Having never seen a P10, my blindness then became a challenge. I had no idea what one looked like, though I could roughly envisage the shape. I found a picture on Rega’s site and printed it to be cut from card so I would have a shape to feel. Using the measurements I did know, I was able to calculate that the image was roughly 75% to scale. Using this information, a lot of guesswork and some hitherto undiscovered artistic skill, the key points were plotted and a mockup drawn for both the brace and the plinth.
These were cut as 18 mm MDF templates. The initial plan was to produce this turntable without the aid of CAD and CNC machinery as I was working to a tight budget. In the end these templates were used to construct the first prototypes. But to do this project justice required a level of accuracy and precision that only a machine would be capable of.
My results from manual machining were to a high standard, but they were not exceptional. I wanted to achieve a level of perfection that was proving unachievable with a handheld router and pencil-drawn templates. I needed the help of CAD and CNC. To describe my CAD skills as lacking would be significantly overstating my abilities. This project was far too complex for me to produce something useable.
Thankfully Gary (surname undisclosed for privacy) had made contact with me via this site having seen the projects here, and him and I had corresponded several times since on various ideas and projects and struck up a friendship. Gary produces exceptional work with a 3D printer and has tremendous skill with CAD software. Having sent him scans of the existing templates, exhaustive dimensions and some reference material, Garry produced the CAD templates for this project. We went through a few iterations and optimisations.
The next challenge was getting the parts machined. Not many machinists are willing to work with unusual materials for a one-off project, and in most cases the setup costs alone make the cost prohibitive. I reached out to Tim Allen of gig.ink. Tim produces custom guitar scratch plates, drum skins and speaker covers. My Bat Strat and the guitar I produced to fundraise for the Save Our Venues campaign both feature plates produced by Tim.
A quick eMail later and Tim agreed to produce 8 mm acrylic templates for the project. Not only that but he had a CNC machine at his disposal, and a colleague willing to put it to use. A pack of materials was duly sent on its way to him and returned in the usual record time perfectly cut to the exact dimensions.
Many parts had to be produced by hand, however. The braces and motor mount were produced using templates and a router, the motor mount carefully finished on, of all things, a wood lathe. The assembly was done entirely by hand. Critical parts for the drive system and the conical feet were produced and modified both by local CNC turning companies and Tangospinner of Argentina.
Looking at the pictures you may think this is just a simple record player. But in reality it is a complex piece of engineering, and has pushed me mentally and my skills and barriers physically at every step of the way. building something like this as a one-off is no small undertaking especially when you don’t have a team of engineers behind you and a reputation that brings most manufacturing companies within your reach.
Credits
I couldn’t have made this project happen without the help of several people and it is only right to give credit where it is most certainly due. Firstly to my aforementioned long-suffering father Tim, who has the patience of a saint and was instrumental in the initial designs for this project. Tim spent many an hour transferring the ideas in my head onto paper, cutting initial templates to the drawings and carefully cutting the various CAD mockups to produce tactile versions so that I could better visualise what I was creating. Most of my designs are produced straight from the image in my head directly to the material I’m working with, but this project presented significant visual challenges that only great teamwork could overcome.
Secondly to Gary for his tireless work and late nights drawing the CAD templates. Gary also produced the artistic mockups you see here, and contributed some of his own design ideas including the smoothed brace curves and further refinements to the plinth.
To Russel who also helped with the bracing designs. To Tim Allen for the machining of the routing templates, the plinth and braces of prototype 3. To Mark who suggested the name ‘Leoht’. To Colin of Collaro for the mat, and Simon & Gary of IPT who manufacture the RigB 3R cartridge body.
To Emkay Plastics for supplying perfectly machined Rohacell offcuts at very reasonable prices, without which this project wouldn’t have been financially possible, and who continue to support the project. To Gus and his Argentinean machining firm Tangospinner. To the technical advisors and sales teams of Easy Composites, CTA Ltd, Permabond, Direct Plastics, Simply Bearings and International Decorative Surfaces (IDS) Ltd.
And last but not least, to Roy Gandy and Phil Freeman of Rega for their influence, for openly discussing the materials and methods they use and their tireless work in advancing vinyl replay. And, of course, to Rega’s sales team. Were it not for their continued shunning of my review publication and disinterest in loaning review units, I might never have embarked on this project and wouldn’t be enjoying the rewards. They lost out on a lot of product exposure but in doing so pushed me to devote a huge amount of time and effort to this engineering effort. Perhaps Leoht will provide inspiration and some of the developments I’ll make going forward will be mutually beneficial, so I guess we all win in the end. I raise a glass to you all.
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