Turntable Theory on the Optimal Turntable

[MrC.]

Some years ago I took an interest in a turntable from Versa Dynamics, now defunct, https://versalab.com/VERSADYNAMICS.html,
The owner and designer, John Bicht, gave an interview, attached, about turntable design that emphasized stiffness over internal damping- The main idea was that a turntable is a system that is only optimized when the vinyl is coupled to the cartridge stylus by a rigid system it will zero out external vibration.

Imagine we substitute your eyes and a computer screen for the vinyl and the stylus. If you’re on a boat going up and down on the sea, with your laptop in front of you, both you and the laptop are moving at the same time so your eyes don’t need to go up and down to focus on the laptop. If you sway in your chair your eyes will have to correct, but if your head were strapped to the seat, the seat bolted to the floor and your laptop glued to the table also bolted to the floor, it would prevent any difference in movement between your eyes and the laptop thus nullifying the effect of external motion. This is the argument for rigid coupling of the bearing to the tonearm, and against the idea of arm pods, air bearings and dissimilar materials between plinth and arm boards. Anything that decouples the bearing from the tonearm, or introduces materials that decelerate the propagation of external vibrations between the plinth, the bearing and the tonearm are to be avoided. The need for isolation of the whole system from external vibration is a different discussion. In a later post I’ll add on thoughts of turntable designs that adhere to these principles, but few designs follow this simple engineering logic.

 

[MrC.]

Pt. 2.
What then makes up an ideal system for a turntable? In a practical sense you want a bearing system that holds the platter rigidly in place to a bearing that can in turn be rigidly coupled to the tonearm. In practice this bearing would be a shaft in a sleeve of exacting machining to make an oil, grease or even an air layer act as a rigid component. A typical air bearing that lets the platter move side to side without a stable central shaft will not do. A floating bearing that permits oscillation up and down as well is the worst of all. Magnetic assistance with a grounded center shaft should be fine as it simply lowers the spindle to plate pressure but maintains rigid coupling between the platter and bearing. A vacuum hold down is also a good idea with a clamp hold down as good as its implementation to secure vinyl to platter to bearing.

 

[MrC.]

Pt. 3 The Plinth

Instead of talking about a plinth, let’s instead discuss it as it is, the bearing to tonearm interface. Whatever we call it we want it to have certain aspects and properties. The main aspect is that it is rigidly coupled to the bearing at one point and the tonearm at the other. The property that is most important in this goal is stiffness and a lack of resonance meaning we do not want the plinth to resonate at a resonance frequency of the bearing, the platter, the tonearm, the cartridge or stylus. Whatever the material chosen it must be uniform between the bearing and tonearm to avoid a dissimilar wave propagation of vibration between the two.

 

[PeterA]

This is an interesting thread. When you say tonearm, do you really mean the arm board, the platform to which the tone arm is mounted?

I agree that everything should be rigid, so there is no relative movement between the tone arm mount and the platter bearing. In my particular turntable, the material is all the same, but I don’t think that is a requirement. The same material of different dimensions will have different resonant frequencies just like different materials. Are you suggesting that the different resonant frequencies create relative movement in the system and should therefore be avoided?

In your boat analogy, everything is rigidly fixed so there is no movement, but the materials are all different. How do things like record mats and motor drive typology affect your theory? And what about the effect of mass on both the resonance of the system and on the inertia of the platter?

It’s a fascinating topic and I look forward to the discussion as it develops.

EDIT: I just read the link to the designer’s essay. He used constrained layer dampening and air bearings. And his designs look like they are low mass.

 

[dan31]

I guess this is in league with Roy Gandy’s thoughts from Rega. Perhaps a Rega Naiad.

The Rega Naiad Turntable – a product unlike any other

A product unlike any other, created to push Rega’s philosophies to the extreme and prove beyond doubt that our lifelong mantra of ultra-light weight, high rigidity plinths and the use of key materials in key areas are paramount in constructing any serious performance turntable.

www.rega.co.uk

 

[analogsa]

Yet, there are plenty of examples where the stiffness dogma is broken, but the sound does not appear to suffer. What about air-bearing tonearms? Should those be bolted down stiffly, or is a free standing pod ok?

 

[MrC.]

Pt. 4 - The Tonearm
If we follow the stiffness principle to its conclusion then we want a tonearm whose mounting point is fixed to the plinth and whose arm is stiff enough to prevent resonance. No arm pod that is separate from the plinth and to the extent an air bearing is used it would be a higher pressure air bearing that would work on a thin pressurized layer of air that would itself be stiff. A radial arm would be stiff and therefore either short in length or massive to maintain stiffness. The aforementioned Versa Dynamics design used a high pressure air bearing of a sleeve on a rod, to transport the cartridge on an approximate 1” tonearm, from side to side across the record. Simon Yorke did something similar with his Aero Arm. Frank Kuzma did a longer arm with his air suspension but in all cases the arm slid on a high pressure air film, thus lending it stiffness from the pressure keeping the air bearing sleeve away from the central rod. The last magnesium SME arms, Kuzma 4 point and the more recent SAT arms employ super stiff arm tubes. The value of this stiffness would be lost, however, if not properly coupled to the plinth or bearing housing. Either a direct support from the bearing to the tonearm or a plinth of uniform material is needed to lock in these components to one another. A separate arm pod May receive external vibrations differently from the bearing and therefore it is questionable whether this could work well.

 

[MrC.]

This is an interesting thread. When you say tonearm, do you really mean the arm board, the platform to which the tone arm is mounted?

I agree that everything should be rigid, so there is no relative movement between the tone arm mount and the platter bearing. In my particular turntable, the material is all the same, but I don’t think that is a requirement. The same material of different dimensions will have different resonant frequencies just like different materials. Are you suggesting that the different resonant frequencies create relative movement in the system and should therefore be avoided?

In your boat analogy, everything is rigidly fixed so there is no movement, but the materials are all different. How do things like record mats and motor drive typology affect your theory? And what about the effect of mass on both the resonance of the system and on the inertia of the platter?

It’s a fascinating topic and I look forward to the discussion as it develops.

EDIT: I just read the link to the designer’s essay. He used constrained layer dampening and air bearings. And his designs look like they are low mass.

His air bearing for the tonearm is a high pressure bearing which he describes as needin 5lbs pressure to move 250 millionths of an inch. The platter bearing he describes as ten times stiffer. You can do this with high pressure air if the spindle is in a well that is supported on its sides and bottom by a film of air that is microscopic and highly pressurized. In practice this is difficult to implement as his air compressor would extract water from the air which could foul the bearings and the high pressure hose to the tonearm could be too stiff to allow free movement. Constrained layer damping was employed to keep the individual components from ringing like a bell, but did not interrupt the linkage between the bearing and the tonearm.

 

[MrC.]

I guess this is in league with Roy Gandy’s thoughts from Rega. Perhaps a Rega Naiad.

The Rega Naiad Turntable – a product unlike any other

A product unlike any other, created to push Rega’s philosophies to the extreme and prove beyond doubt that our lifelong mantra of ultra-light weight, high rigidity plinths and the use of key materials in key areas are paramount in constructing any serious performance turntable.

www.rega.co.uk

And the Atmasphere 208

https://www.atma-sphere.com/Products/Atma-208.php

 

[microstrip]

And the Atmasphere 208

https://www.atma-sphere.com/Products/Atma-208.php

Ralph Karsten recently addressed the rigidity subject when debating the tonearm - plinth interface in the Technics SL1200, referring to the Atmasphere 208 .

 

[MrC.]

Pt. 5 - Damping

Now that you've made a rigid coupling between the bearing and the tonearm what do you do about the resonances in the plinth. You can glue dissimilar materials together to cause the resonances of the plinth material to cancel them out in constrained layer damping as is done by Technics in the SL 1200 or 1300. You can pour a resin into voids of a plinth or fill voids with sand or lead and oil.
The Technics also uses dissimilar materials of Aluminum and brass on the platter, which have different resonance points. Rega in its Naia, uses a ceramic brace on the top and bottom of the plinth that couples the platter to the tonearm. In between is a layer of rigid foam which has the benefit of low mass and air voids throughout, so it does not resonate at any audio frequency and will not pick up vibrations from the air. The denser material you choose for the plinth, the more risk you have from ringing, especially if metal is involved. What cannot be done, if stiffness is to be preserved, is to break the connection between the platter and the cartridge with any soft material in between the two. That means a felt mat, a cork mat, or even a soft rubber mat should be avoided. Arm boards that couple with a rubber gasket or soft design also break the connection between the bearing and tonearm. Arm board of dissimilar materials to the plinth may also alter the propagation of vibrations enough to introduce a difference in the vibration between the bearing mount and the tonearm mount, which if it shows up at the needle, this difference will be amplified as distortion.

What then to use as a platter mat? It seems that something that couples well with vinyl, being neither too hard or too soft, would be best. In earlier iterations, the Brinkmann Bardo had a vinyl layer bonded atop the thick aluminum platter. This turntable also had the benefit of a minimal plinth, and the same material for the plinth as the arm board and platter. If a rigid coupling is to be made then a record weight or screw down or friction clamp should be employed to directly couple the record to the platter. If a loose or separate mat is to be used, like the copper mat from Micro Seiki, or other hard mat that sits atop the platter, then it seems some effort should be made to couple it to the platter, with an adhesive or other bonding method, to ensure stiffness in the system.

Damping only deals with the desire to prevent the platter, the plinth or the bearing from ringing or resonating. The question of isolating the turntable from extraneous outside noise is a different matter entirely,

 

[hb22]

For me personally, an air bearing is the perfect solution for an analog turntable. Of course, it is very difficult to implement it well into a good whole in the operation of the turntable. It is not easy.
The biggest problem with a turntable/tonearm is (apart from the direct drive motor radiation); when the needle travels along the groove of the vinyl, it causes terrible vibrations! Good design equalizes these unwanted vibrations to the maximum in a way that only the vibrations that were originally recorded on the vinyl remain. This is where the cartridge, tonearm and platter work together.

 

[tima]

Everything has a resonance frequency. I thought the idea was to avoid vibrations that match the resonance frequencies of the various components in a turntable so those resonances are not amplified.

 

[mtemur]

Dear @MrC,

I agree with you on all points, but I should remind you that using harder, stiffer, and heavier materials for the plinth helps reduce resonances. Simply put, relying on high mass is an effective way to eliminate vibrations. Contrary to common belief, such materials do not ring when they are thick enough and/or treated with anti-resonance coatings.

As you explained perfectly, tonearms should be coupled directly to the arm base, and the arm base should be rigidly connected to the plinth. There should be no rubber O-rings, gaskets, or other elastic materials in between. Additionally, the bearings of the tonearm should be rigid. This is crucial to keep the cartridge steady as it tracks highly modulated grooves.

For these reasons, I’m not a fan of unipivot tonearms—they cannot hold the cartridge steady in the groove. The old SME 3009 and 3012 arms, which use a knife-edge bearing, are better in this regard but still fall short of what a proper bearing should be. Another issue with the SME 3009 and 3012 arms is the use of O-rings at the mounting plate that decouple the arm from the arm base. When you remove those O-rings, you begin to hear the real character of the 3012, which is slightly thin and edgy.

 

[PeterA]

Dear @MrC,

I agree with you on all points, but I should remind you that using harder, stiffer, and heavier materials for the plinth helps reduce resonances. Simply put, relying on high mass is an effective way to eliminate vibrations. Contrary to common belief, such materials do not ring when they are thick enough and/or treated with anti-resonance coatings.

As you explained perfectly, tonearms should be coupled directly to the arm base, and the arm base should be rigidly connected to the plinth. There should be no rubber O-rings, gaskets, or other elastic materials in between. Additionally, the bearings of the tonearm should be rigid. This is crucial to keep the cartridge steady as it tracks highly modulated grooves.

For these reasons, I’m not a fan of unipivot tonearms—they cannot hold the cartridge steady in the groove. The old SME 3009 and 3012 arms, which use a knife-edge bearing, are better in this regard but still fall short of what a proper bearing should be. Another issue with the SME 3009 and 3012 arms is the use of O-rings at the mounting plate that decouple the arm from the arm base. When you remove those O-rings, you begin to hear the real character of the 3012, which is slightly thin and edgy.

Mtemur, in your opinion, what arm and turntable best meet these ideal criteria?

 

[mtemur]

Mtemur, in your opinion, what arm and turntable best meet these ideal criteria?

IMHO most high-end, high-mass turntables meet this criterion, with just a few exceptions—mainly those that incorporate a tonearm tower. I don’t have first-hand experience with your turntable, but based on the pictures and videos I’ve seen, it appears to match this criterion perfectly.

Regarding tonearms, most models with race and gimbal bearings also meet this standard. SAT, Acoustical Systems, Kuzma, and Glanz are great-sounding examples that come to mind. The SME V is another good example in terms of meeting the technical criteria, but it doesn’t offer the same level of performance or sound quality as the others I mentioned. I also have some reservations about air-bearing linear trackers.

 

[dan31]

Just a note on the discussion. Several opinions are based on the ideal or theoretical design. Implementation is everything. Most designs have varying degrees of comprmise.

 

[MrC.]

Pt. 6 - The Drive Unit

This is the area that causes me the most hesitation as all my observations are anecdotal and none of them are based in any particular science I can find. I own idler drive tables, belt drive and direct drive. While I have my own preferences I wonder why and what causes what I hear. I have a preference for high mass platters driven by direct drive or idler drive. Win sound made a magnificent idler drive deck that I thought was amazing. VPI’s Classic direct is another standout. My current reference is a Brinkmann Bardo. Thomas Schick’s idler drive is also lovely. What is most engaging for me is the leading edge of the sound which I believe, without evidence, is only faithfully reproduced when the stylus sees a platter driven against it at high torque. The absolute minuscule pressure of the tiny needle on the vinyl walls of a record still seem to deflect the platter drive system enough to be heard. I have zero explanation for this but having heard it myself, repeatedly, it is something I cannot deny. Rubber belts and thread drive might show steady speed stability but my ears are telling me something else is going on. If forced to guess I would suppose that the direct torque on the platter, without an elastic or slipping intermediary like a belt or thread shows up as an explosive transient as opposed to a more muted transient from a belt or thread. Audio note in its materials for their three motor turntable claimed that the angular torque from the three motors was equivalent to an angular momentum of an equivalent platter weighing 1/4 ton. I wonder at the equivalent angular momentum for the idlers and direct drives mentioned in this thread. The direct coupling of motor to platter or through a rigid wheel, just seems to work better.

I cannot define why it is better but for me a direct drive, rim drive or idler drive is best. A belt drive using a woven silk belt can be good but only when left without slack in the system. These are only opinions nor can any be defended from your own preferences.

 

[ssfas]

Size and weight doesn't reduce resonances, it just makes matters worse when they do resonate. I learned this in my first ever job, aged 17, measuring vibrations of heavy plant on oil rigs. I'd get locked in a big box containing, for example, an Avon jet engine going at full speed with a bag of transducers, some superglue and a tape machine.

I not heard a massive load of turntables, but Matthias Lück from Brinkmann with a totally pimped system and one of his copper lacquers was a lot of fun. He could sell ice to eskimos, alas I didn't buy a Brinkmann. Touraj Moghaddam of Vertere is the most annoying because he prefers the sound of his own voice to music.

There are so many elements: deck, plinth, arms, cartridges, feet the supporting structure, ac power the floor, the weather and no doubt more. Mine sounds good, looks better and everything about it is in moderation, so I feel good about it and I've got a head start on it sounding great. Which it does. To me, anyway. And nothing else matters.

 

[PeterA]

Pt. 6 - The Drive Unit

This is the area that causes me the most hesitation as all my observations are anecdotal and none of them are based in any particular science I can find. I own idler drive tables, belt drive and direct drive. While I have my own preferences I wonder why and what causes what I hear. I have a preference for high mass platters driven by direct drive or idler drive. Win sound made a magnificent idler drive deck that I thought was amazing. VPI’s Classic direct is another standout. My current reference is a Brinkmann Bardo. Thomas Schick’s idler drive is also lovely. What is most engaging for me is the leading edge of the sound which I believe, without evidence, is only faithfully reproduced when the stylus sees a platter driven against it at high torque. The absolute minuscule pressure of the tiny needle on the vinyl walls of a record still seem to deflect the platter drive system enough to be heard. I have zero explanation for this but having heard it myself, repeatedly, it is something I cannot deny. Rubber belts and thread drive might show steady speed stability but my ears are telling me something else is going on. If forced to guess I would suppose that the direct torque on the platter, without an elastic or slipping intermediary like a belt or thread shows up as an explosive transient as opposed to a more muted transient from a belt or thread. Audio note in its materials for their three motor turntable claimed that the angular torque from the three motors was equivalent to an angular momentum of an equivalent platter weighing 1/4 ton. I wonder at the equivalent angular momentum for the idlers and direct drives mentioned in this thread. The direct coupling of motor to platter or through a rigid wheel, just seems to work better.

I cannot define why it is better but for me a direct drive, rim drive or idler drive is best. A belt drive using a woven silk belt can be good but only when left without slack in the system. These are only opinions nor can any be defended from your own preferences.

Mr.C, How does one keep the vibrations from an idler wheel or rim drive from influencing the platter or from migrating to the bearing or arm mount if all the connections are so stiff? I agree about the importance of the integrity of the leading edge or transient, but not all belts are elastic, and not all threads slip. Some motors do have high torque, and some platters are truly massive with high inertia. Their speed is quite stable. To me, the influence of the motor on the platter is very important. Proper speed must be maintained and the motor noise must not reach the platter. The problem seems pretty simple but the right solution and its execution can be very difficult, as was suggested earlier.