At the end of a long phone-call with an Audiophile friend, he mentioned to me that he knows someone that has built a magnificent turntable. A work of love and pure genius. Meticulously designed and very sound mechanical principles. Seeing that we are all a little bit isolated from the rest of the "modern" world and that most of our legends are old and have passed away, I was very curious to say the least. I always wondered why nobody tackled a good solid engineered turntable in South Africa. I mean, really...how difficulty is it to improve on a Linn LP12, Rega 3, or any of those ? The call was made and here starts the story....Ill let Lance tell his own story with a few notes here and there from myself....
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, thereby ensuring the highest possible performance and specification for every element of the design.
The aesthetics of the turntable, I consider to be a vital ‘functional’ part of the design, thereby being 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 was acceptable.
Each component would be made to specific tolerances and finished to perfection, even the components that are inside and underneath the unit.
Throughout the development of the turntable I have had support, encouragement and technical assistance from some very fine people!
I would like to thank, Schalk Havenga, Grant Thorburn, Roy Wittelson, Chris Klopper, Roland Cook, my son Luke, who helped with some complex engineering calculations and my family for putting up with me for spending so much time in ‘turntable heaven’!
The prototype, was completed to the point of first switch on and play by May 2016. With a deep breath and a glass of wine in hand to steady the nerves, I played the first tracks using my old SME Series 111 arm and a Grado Gold cartridge and immediately realised that the basic functional aspects of the turntable were working perfectly and even though the standard of tonearm and cartridge were limited, I heard many encouraging signs.
The last eight months since then, have been a listening/testing and tweaking phase. Many elements have been changed and improved along the way. I now find myself listening for extended periods and deeply enjoying the music, (when the hairs on my arms stand up, I know it’s doing the trick!) The meticulous attention to detail throughout the design and prototype building process and logical engineering approach have paid off.
Below are paragraphs that broadly describe various elements, components and materials that have been used on the prototype turntable.
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.
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.
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.
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 travelling upwards.
The gap between the magnets is set according to the weight of the platter assembly, thus allowing 1.5 kg of force to exert 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.
The platter consists of numerous components made from differing materials;
1. 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.
2. 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.
3. The middle platter disc, made of aluminium with a central sleeve that centralises the disc and acoustically de-couples it from the central boss.
4. The upper platter disc, can be made from various materials, each with a different tonal quality. The options include acetal, ertalyte, and aluminium.
5. Each of the three layers are separated by an intermediate layer of felt, these layers insulate vibrational energy that may emanate from the turntable and the main platter bearing.
6. 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.
7. The platter assembly weighs between 17.5kg and 20kg depending on the choice of materials.
8. 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.
9. The various metal components can be finished to individual preference.
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.
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.
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 and available 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 depending on taste. 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.
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 machined tolerances, the gap between the bearing surfaces and the viscosity of the oil are the key factors in determining the accuracy, the amount of friction and the durability of the bearing.
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.
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 15way D-sub connector for the motor connection, a fuse, and USB socket. The USB socket is specifically for connecting 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.
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.
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 17 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 13core cable via a D-sub connector.
Internally, there is an eight to one speed ratio reduction belt and pulley system. There are three 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.
The motor is a 24volt 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 controller constantly monitors the motor shaft and ensures that it maintains the exact pre-programmed speed. A continuous stream of data flows from the motor to the controller and back.
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 when the turntable starts.
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!
The ‘Revolve’ name is laser-engraved on the top of the wooden 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;
1. The hardwood for the plinth and the finish applied, this can be mirror gloss, satin, or natural.
2. 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 finished to personal taste, options include chrome or gold plating, anodising or sprayed finish.
Two adaptor plates will be provided 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.
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 is 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 its stand.
The overall weight of the turntable is approximately 65kg and therefore the equipment stand must be capable of supporting that weight.