The Revolve turntable project, how it unfolded.
by Lance Dixon.
2013-2017.
I love turntables!
All those of you that grew up in the initial vinyl era will understand exactly what I mean when I talk about turntables, how they attract our attention, engross us in the myriad of intricate mechanisms, the process of caring for and playing records and sometimes we just love to look at them!
I refer to the ‘vinyl era’ but having said that, analogue sound reproduction never actually stopped, in fact, while CD’s and now more recently streaming and other digital storage/playback systems have become the prevalent sources of music reproduction, the analogue boys were quietly continuing to improve their equipment. The quality of the vinyl records has also improved. The result being, that now, many music lovers worldwide are returning to analogue as their first choice for true high-end music reproduction. Figures are showing that vinyl sales are increasing at around 50% year on year.
What we have now, are vastly improved turntables, tonearms, cartridges and records and the added benefit of modern recording techniques, the sum of which record and playback music of exquisite quality. There is something inherently special about listening to analogue playback and can be described as smooth, natural, non-fatiguing and musically and emotionally involving.
Needless to say, I have always aspired to own one of these newer technically advanced turntables.
My background
After matriculating at Westerford High School in Cape Town, I had the privilege of studying furniture design and technology at The London College of Furniture. The course covered all the various materials and techniques used in furniture making from meticulously handcrafted masterpieces right through to high volume production. I was particularly influenced by the ‘Furniture Designer Craftsmen’ as they were known at the time. They designed and made furniture that could be described as functional sculpture, each piece being a work of art of the very highest quality.
Life does tend to throw curve balls at you, so I found myself involved in commercial design and manufacture of various products and machinery, and not much to do with furniture. So, for some 30 odd years I have accumulated knowledge and experience in a wide range of manufacturing techniques and processes.
Music has been a passion of mine since my teens, having briefly flirted with playing the guitar I realised that my abilities were better suited to the design field. I realised that to play music beautifully with personal touch with intimate knowledge of your chosen instrument, requires an inordinate amount of time, practice and dedication. It is for these reasons that I have the greatest respect for the musicians that are able to transport us into another world with their exquisite talent.
In 1997 I was asked by the local South African hi-fi manufacturers, namely Steinhart Audio, Valve Audio and Sonor Audio if I would be prepared to be their agent in the Western Cape. I took a deep breath and said yes. My association with the late Gunter Steinhart, Roy Wittelson and Schalk Havenga has led to a wonderful and rewarding experience in the world of high-end music reproduction.
The turntable idea
Sometime in mid 2013 I began to mull over the idea of making a turntable. I felt that I would never be able to afford one of those magnificent machines, so the question was, would I be able to design and build a turntable that could perform to the highest standard that I desired? It could be a hobby with the added bonus of listening to wonderful music at the end.
Endless hours of research followed as I began to accumulate knowledge of what makes a good turntable. During this process, it became apparent that while most turntable designers/ manufacturers tend to agree on the essential functional requirements, the design solutions are quite varied and sometimes contradictory. This of course makes the subject all the more fascinating!
All designs begin with some ‘doodling’ as I call it, rough sketches and ideas. Through research and much discussion with knowledgeable friends, I began to identify and choose the functional elements that could be used in the design. Once these initial basics were identified, the next task was to talk to engineers about the possibilities of local manufacture.
By the time I established that this task could be possible, I was already completely hooked by the challenge.
I feel privileged to have had the opportunity to do this project, as I have loved each and every aspect of the journey so far.
The design
It is impossible to know how much time this has taken, the cad drawing time alone was over 1700 hours last time I checked, not to mention the research, design, prototyping etc. As the design developed so my excitement increased, this project was drawing on my furniture and engineering design background and was including many new technological elements that required much new learning! I am still learning and looking forward to the testing phase which I expect to reveal some interesting answers to the many questions that I have.
The brief to myself was to design a turntable whereby all the functional requirements perform considerably beyond what would be considered necessary for high-end music playback, a big ask, and it remains to be seen and heard whether that can be achieved.
The aesthetics of the turntable, I consider to be a vital ‘functional’ part of the design, it needs to be something that you love to look at, touch, operate and listen to, a ‘whole’ experience. The design is a blend of traditional (read correct) handmade woodworking craftsmanship with precision engineering, some visible and some hidden. The look could be described as ‘classical’, elegant, understated, fit for it’s purpose. There is no unnecessary embellishment or bling which in my opinion are artificial and tiresome. My personal design approach is to blend form and function in a logical manner in every detail, and in this project, no compromise is acceptable.
Four years into the project, (mid 2017).
Four years after that initial idea I am proud to say, there is a working prototype that is performing rather well despite the fact that it is in it’s very first configuration. At present there is an old SME series three arm with a Kiseki Blue (old version) cartridge on one arm board and an Audiomods with a Dynavector DV-10X5 cartridge on the other arm board, (kindly lent to me by my friend Roland Cook). This system, with good albums is making the hairs on my arms stand up, that means that the music is getting through to me, whether it be Ray brown and Lourindo Almeida on ‘Audiophile legends’, or Paganini ‘Diabolus in Musica’, or pink Floyd’s ‘The Wall’. This certainly indicates to me that the turntable in its infancy is doing a lot of things right! I look forward to be able to try a really high-end tonearm/cartridge combination that will reveal more detailed information.
The next phase of testing will include the following.
- Different upper platter materials, this will include Ertalyte and aluminium.
- Different insulation layers between the three platter discs.
- Ball and thrust plate material combinations.
- Oils of varying viscosities in the main bearing.
- The isolation and vibration absorption effect of the media that will fill the plinth.
- Further high accuracy platter speed measurements with some heavy bass passages.
I am expecting that these tests may lead to many more, and at this stage it is not possible to predict what sort of time this may take. The successful start is highly encouraging and is indicating that many of the design/engineering features are performing as they are meant to.
The time will come, hopefully sooner than later! That The Revolve Turntable will be a marketable product.
Description of the prototype.
Below are paragraphs that broadly describe various elements, components and materials that have been used on the prototype turntable. Many of these components may change as the turntable is tested to establish which options perform best.
Platter assembly
The platter consists of numerous components made from differing materials;
- A central boss made of brass that fits over the bearing shaft. It has a flange with six bolt holes to enable the lower platter disc to attach to it.
- The lower platter disc, made of steel is bolted to the central boss and the two are machined together to ensure absolute concentricity. The underside of the lower platter disc is machined to accommodate the upper ring magnet assembly.
- The middle platter disc, made of aluminium with a central sleeve that centralises the disc and acoustically de-couples it from the central boss.
- The upper platter disc, can be made from various materials, the prototype will be tested using Acetal, ertalyte, and aluminium, to understand the effect that these materials have on the sound.
- Each of the three layers are separated by an intermediate layer, various materials including felt, cork, graphite etc. will be tested to establish which may be best in terms of insulating vibrational energy that may emanate from the turntable and the main platter bearing.
- The ‘stacked’ assembly thus has several acoustic de-coupling layers between the bearing shaft and the upper surface that is in contact with the record.
- The platter assembly weighs between 17.5kg and 20kg depending on the choice of materials.
- The mass of the platter creates sufficient inertia to overcome any variations in frictional resistance created by the stylus and vibrations in the belt that could otherwise affect the speed of the platter.
- The various metal components can be finished to individual preference.
Magnetic levitation
Due to the high mass of the platter assembly, magnetism is used to reduce the amount of force on the thrust bearing. This is achieved by using a pair of ring magnets, encased in a shield assembly to minimise the magnetic flux from traveling upwards. The gap between the magnets is set according to the weight of the platter assembly, thus allowing approximately 1.5 kg of force on the thrust bearing. This reduces the bearing friction and thus the level of vibration from the bearing. The added benefit of this is increased bearing life. The Neodymium magnets that are used, typically lose only 0.5 % of their strength in about 100 years. The lower platter disc is made from steel which forms an additional shield that prevents the magnetic flux from reaching the record surface.
Main Bearing
The main bearing consists of a 20 mm diameter precision ground stainless steel shaft, inside a 60 mm diameter brass housing, lined with polymer bushings. There is a reservoir of oil that ensures that the surfaces are constantly submerged. The tolerances and the gap between the bearing surfaces and the viscosity of the oil are the key factors in determining the accuracy, friction, and durability of the bearing. These factors are in the process of being tested on the prototype.
A ball is used on a thrust plate at the bottom. The combination of materials used is for these is also being tested on the prototype.
The bearing assembly is attached with six machine screws to a large mount which is in turn attached with six more screws to the base plate.
Base plate
The base plate is 15 mm CNC machined aluminium. It has mounting points milled for the three feet, main bearing mount, two arm board pillars, and the connectors that attach the wooden plinth around the perimeter.
Feet assemblies
There are three feet, two at the front and one positioned below the perimeter of the platter at the rear.
The rear foot assembly is fixed while the two front feet are adjustable.
Each assembly consists of an 80 mm diameter foot that has a silicone pad underneath to provide a stable grip on the surface. A spike locates on a central countersunk point on the foot. The spike reaches up to just below the top surface of the wooden plinth. The spike is threaded at the top and screws inside the top section of a sleeve. The sleeve has a lip at the bottom which locates under the base plate. The turntable thus ‘hangs’ on the three sleeves. The two front spikes have slots to adjust the height and lock screws to fix the position when the turntable is level. These are accessible through removable caps located on the top of the wooden plinth.
Each of the sleeves becomes surrounded by vibration absorbent media, (see explanation elsewhere)
Wooden base/plinth
The plinth is made of solid wood, the shape accommodates the front feet assemblies and the two arm board pillars at the rear.
The construction consists of a lamination of five frames with ‘finger joints’ in the four corners. The laminates are 20 mm thick and the finished wall thickness is 28 mm. The frames are joined by 80 dowel joints for long lasting stability and strength. The top is also made from solid wood. The top is joined to the sides by means of connectors that allow for seasonal movement of the wood. All aspects of the plinth design conform to correct craft woodworking technique.
The prototype is made from Jackaranda, however any desirable hardwood may be used.
The finish is a process of ten successive layers of sealer and two-part polyurethane, the finish of the prototype is mirror gloss, but could be a satin or natural matt finish. The materials used and finishing process has been selected for superlative quality and durability.
The plinth is joined to the aluminium base by the same type connectors that are used for the top to allow for seasonal wood movement in relation to the aluminium base. The wooden plinth does not come into contact with any components other than the aluminium base plate, it therefore has no influence on the sound quality of the turntable.
The top of the plinth has a circular removable cover that is slightly smaller than the diameter of the platter. This cover allows access to the inside of the base assembly, primarily to allow for filling the base with vibration absorbing media.
Vibration absorbent media
The base section is filled with a mixture of finely ground garnet and lead ( or possibly Bismuth) pellets. This mixture adds considerable mass to the turntable and absorbs any vibrational energy that may occur. Vibrational energy can occur from various sources, it could come up through the stand, it can be ambient airborne energy or from the bearing or even the arm board pillars. Each of the following components are dampened by the media; the base, wooden plinth, feet assemblies, main bearing assembly, arm board pillars.
The vibration media is sealed inside the base plinth.
Arm board pillars
The two arm board pillars are securely mounted on the base plate in the two rear ‘corners’ of the turntable. They consist of 40 mm diameter solid steel rod and protrude through the base top without touching the wood of the plinth. There is a gasket that seals the opening between the wooden top and the pillars. The pillars are completely surrounded by the vibration absorbent media.
Arm boards
There are two arm boards, allowing for two differing tonearm and cartridge combinations.
The arm boards are CNC machined from solid aluminium to a finished thickness of 20 mm. The finish can be plated, anodised or sprayed to suit individual preference.
The arm boards are bolted to the pillars by means of a substantial cap screw, this enables the arm board to be rotated and set in position according to the required centre distance for a given tone arm.
Any type or length of tonearm can be mounted, utilising purpose made adaptor plates.
Motor
The motor is a 24 volt DC type with precious metal brushes and graphite bearings, manufactured by Maxon. This type of motor was chosen for many reasons including high precision, zero cogging, silent running and impeccable quality.
The motor is digitally controlled by a separate control board and the speed is governed by an on- board quartz clock. The motor speed is therefore un-affected by voltage and frequency variations that occur on the mains supply.
The motor speed is pre-programmed for each turntable using Maxon propriety software. A ramp-up from zero to either 33.33 rpm or 45 rpm is also pre-set to take approximately 5 seconds, this reduces stress on the belts and the load on the motor.
Maxon motors are used where absolute controllability, precision and durability are paramount, such as satellites, the Mars Rover, Formula 1, medical and measuring equipment, and un-surprisingly, several of the very best turntables in the world!
Motor pod
The motor pod refers to the housing that contains the motor and a step-down belt pulley system. The housing is made of steel to provide substantial mass which provides a stable, vibration free platform for the motor and internal mechanism. The pod assembly weighs 15 kg.
The pod has a silicone pad underneath for stable grip, and is positioned centrally, approximately 10 mm from the back of the wooden plinth. The out-board, high mass pod eliminates any internal vibrational energy from affecting the turntable.
The pod is connected to the control unit by a 13 core cable via a d-sub connector.
Internally, there is an eight to one speed ratio reduction belt and pulley system. There are two silicone ‘O’ ring belts that track on grooves on the motor pulley. The pod is enclosed and there is an external pulley attached to the intermediate shaft which in turn becomes the drive pulley for the platter.
Drive system
The prototype as mentioned has a multiple ‘O’ ring belt system with an intermediate step. This provides and overall reduction ratio of approximately 55:1. Therefore at a platter speed of 33.33 rpm the motor shaft speed is 1833 rpm.
The motor speed is programmed once the turntable is complete and this enables fine setting allowing for minute dimensional variations such as the thickness of the plating/finishing on the lower platter disc ( the belts run around the lower platter disc). The platter speed is measured using an optical sensor which is linked to a quartz based comparator circuit which determines the platter speed precisely.
The net result of the reduction ratio is a high degree of speed accuracy with low torque applied to the motor. The motor therefore sees a load at the lower end of its specification and this in turn ensures extended motor life.
Testing will be done on the prototype using different belts, including flat belts to establish if there is any performance advantage with a particular type.
Control unit
The prototype control unit has a wooden laminated fascia of identical shape to the front of the turntable.
The controls consist of, a power on/off button and a led to indicate that power is switched on. There are two rotary knobs, one to switch between 33.33 rpm and 45 rpm., and the other to start/stop the motor. The knob assemblies are designed to give a smooth tactile feel to the operation. All these components are purpose made.
The rear panel consists of an IEC 3 pin socket, a 15 way D-sub connector for the motor connection, a fuse, and USB socket.
The USB socket is specifically for connection to a computer in order to program the motor controller, this is done in the workshop as part of the initial set-up and testing.
Finishing touches
The ‘Revolve’ label is made from an off-cut from the wooden plinth. The name is laser-engraved on the wood and the piece is finished to match the finishing process used on the plinth. The badge is positioned centrally in the front of the plinth.
Each turntable will have a plaque attached to the side of the plinth. The plaque will be engraved with the original owner’s name, the date of completion, the serial number and a ‘made by Lance’ signature.
Each turntable will be bespoke, i.e. made to order according to a customer’s preference and therefore no two will be alike. Selectable items will include;
- The hardwood for the plinth and the finish applied, this can be mirror gloss, satin, or natural.
- Each of the various metal components such as the feet, closing caps, platter discs. arm boards, controls knobs and on/off button and the record clamp can be plated, anodised or sprayed.
Two adaptor plates will be made to facilitate the mounting of specified tonearms. Further adaptor plates may be ordered as required.
All the tools required to set-up, and spare bearing oil and belts carefully packaged for future use.
Packaging
The turntable will be packed in a wooden crate. Each of the components will be packed in sequence to enable simple and logical setting-up.
The turntable is heavy and will require two ‘able bodied’ people to lift the main assembly out of the crate. There will be a convenient ‘lifting’ frame under the turntable to assist with the lifting and positioning of the turntable on an equipment stand. The lifting frame is dis-assembled and removed once the turntable is exactly positioned on it’s stand.
The overall weight of the turntable is approximately 80kg and therefore the equipment stand must be capable of supporting that weight.
Setting up
There will be an easy to follow setting up procedure detailed in an owners manual.