Once Analog Turntable Speed - click the following link - onceanalogturntablespeed.pdf
Which is the best turntable motor? - click the following link - bestturntablemotor.pdf
Tonearm Comparisons: Basis Vector 4 / SME V / Syrinx PU3 / Benz Lp Ebony
Belt-Driven, Best Option - My Opinion
On first inspection, a direct-drive turntable is seen as the perfect system. The platter is centre driven (spins like a fan), motor wear is uniform, (good engineering principals).
However, in terms of musical reproduction, a second observation reveals a different story. The motor produces friction and vibration noise that is transfered through the spindle to the record surface and stylus, this results in loss of clarity.
One of the key factors in turntable design is motor isolation, the very reason why the suspended sub-chassis was developed.
For the enthuasiast that is a keen listener, a belt-driven turntable is the best option.
The inertia of a given platter weight will be increased by using a record weight. For example, if a platter weighs 3kg then adding a 1kg record weight will increase the overall inertia of the system. The mass of the platter is distributed over a larger diameter and will store more energy than the smaller diameter record weight, because its mass is concentrated near the centre of the rotating system. However the record weight still effectively contributes to the overall increase in inertia, as if you were using a heavier platter of about 3 1/2kg.
Spindle Diameter, Record Hole Size
Using a "Starrett" hole gauge and a "Mitutoyo" micrometer. I selected 10 pressings dating back to the sixties. Here are the measurements of the hole sizes: 7.390mm/7.290mm/7.270mm/7.230mm/7.400mm/7.340mm/7.325mm/7.206mm/7.360mm/7.346mm. The variation is: 0.2mm/8thou.
I also checked 6 turntable spindles: 7.213mm/7.016mm/7.176mm/7.110mm/7.150mm/7.140mm/7.100mm. The variation is: 0.197mm/7 thou.
Record hole size average was: 7.316mm, (a variation of 0.2mm/8 thou). Spindle Diameter Average was: 7.130mm, a variation of 0.186mm, (this could be rounded off at: 0.2mm/ 8thou).
The worst case for this scenario is the largest record hole: 7.400mm being placed on the smallest spindle: 7.016mm a variation of: 0.57mm/14.5thou.
The consequence of this wouuld be a 0.57mm/14.5thou slack in radius/eccentricity. You could reasonably assume that there would be enough friction to prevent an evenly dispersed 0.57mm hole slack from being a measureable problem.
Correct Bearing Lube
Turntable spindles and housings are machined to close tolerances. In this situation a thin, light-weight oil will penetrate well, forming a consistent film between the close fitting parts.
With significantly reduced friction the spindle turns more freely generating less vibration and enhancing platter momentum. This means less noise is transferred from the spindle to the record surface and stylus.
The result is improved clarity!
SERVICING PROCEDURE - TURNTABLE BEARING
1. Wash out the bearing housing using denatured alcohol or other suitable cleaning agent.
2. Use cotton buds to swab the bottom of the bearing housing until any traces of old oil and dirt deposits are removed.
3. Clean the spindle with an alcohol dampened cloth and allow to dry.
4. Fill the housing to 1/3 of its capacity using a light sewing machine oil.
5. Carefully place the spindle into the housing. Due to a condition known as hydraulic-lock, initially the spindle will only sink into the housing a few millimetres as it sits on top of the oil.
Do not attempt to force down or spin the platter. The platter's own weight will eventually allow the spindle to fully seat against the thrust plate. This process could take several hours (be patient and allow the oil to penetrate at its own rate).
Equal importance is placed on the four divisions; Platter, Bearing, Motor and Plinth. In one sense each component is the most important in maintaining the relationship of the individual to the whole. This relationship is often referred to as symbiotic. A designer's objective should be to place emphasis on the fact that each component is designed to work with the other, a harmonious situation.
The intertia of a heavy platter (once it gets up to speed) tends to make it want to continue rotating at that velocity. Any minor, short variations in motor speed (flutter) will get smoothed out by the inertia of the platter in conjunction with the elasticity of the belt. Very slow motor speed variations (wow) are a problem though, and should be taken care of by using good regulation of the motor power supply.
Another good reason for using a heavy platter is to aid in reducing acoustic resonance from sounds in the air. A light platter can amplify rumble from the motor and bearings. A well designed bearing is critical in any turntable.
In a belt-driven turntable, the correct belt dimensions; length, width and thickness are of the utmost importance. On start up, the belt acts as a clutch; drops to the bottom of the motor pulley, then makes it's way to the top, before settling on the crown, (during this start up time the belt is under stress). The smoothness of this operation depends on several factors; motor torque, belt length, width and thickness. Some turntable builders advise coating the belt with a talcum power to assist in a smooth efficient start up.
If the belt is too short, you will damage your housing with excessive sideway force! Also, if the belt is not the correct length speed stability will be affected, even if the motor is a synchromesh type that locks onto the mains!
Source the correct belt - it will be beneficial for years to come.
Shapes Versus Sound
On the subject of cartridge body materials, do various materials effect sound quality?
To carry this topic further, can the actual shape of a given cartridge change the sound charateristics by altering the casing contour?
If so, would this also apply to a turntable plinth?
If we conclude various materials and shapes will change the sound of cartridge casings and turntable plinths, then it's likely that different glues and finishes will have an affect.
I read an interesting story about a luither who claimed he could make a better violin than Antonio Stradivari. He travelled to Italy and sourced the timber from the very forest that Stradivari cut his. And, returning home he constructed a masterpiece, only to be disappointed. His creation did not match the sound of the original "Stradivarius"!
It has been considered that it was the glue and varnish that Stradivari used that contributed to the unique sound!
LP 12 Compassion
The LP12 is the most successful turntable, since it's introduction in the 70s. With the model the LP12 a prestige State Of The Art record player, with in excess of 360,000 units in just under forty years of business!
For almost four decades the LP12 has remained at the forefront of vinyl reproduction and consequently has been the playback system that all other turntables have been compared.
Most impressive is the fact that since the beginning, Linn has remained loyal to customers offering continued upgrades; spare parts are readily available worldwide!
The compassion that drove me with the Once Analog turntable, and it's make up was and still is the LP12!
The idea of using a record weight/clamp to improve sound comes as no surprise. During playing an LP slippage occurs, and this disc movement results in distortion (loss of clarity).
The variation of movement will vary depending on the mat material. Rubber is the most stable.
Hence the reason my record weight is called a "Disc Stabilizer".
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