Tables That Feature Bearing Friction

Dgarretson,

I addition to the practical difficulties that Dertonarm pointed out there are some good theoretical reasons against using a flywheel at the motor. In all motors motion is produced by magnetic attraction. When there is no drag the
magnetic fields in the stator and rotor will be perfectly aligned. When drag is applied the magnetic fields pull apart and the attraction creates torque. This is a very desirable characteristic in that torque is almost instantly created in response to a load perturbation. I say almost instantly because the rotational inertia in a motor delays the delivery of torque. Any delay in torque delivery adversely affects the motors ability maintain constant speed because the corrective torque is being applied after the fact. The longer the delay the worse the problem becomes.

Belts, particularly stretchy ones, have the same effect. They filter cogging, but also delay delivery of torque. Filtering cogging is a good thing, but it comes at a price. In many cases the fix is worse than the problem. Much better to just start out with a motor that has low cogging.

In addition to the theoretical arguments there is plenty of empirical data that indicates that low inertia motors tend to sound better. That has been my experience.

BTW: Certus turntables use an eddy current brake. The braking force is much greater than what a belt drive mechanism can keep up with.

Chris

Hi Dan_ed, I do not use the Platine Verdier. Furthermore I do not see that I have refered in any way to the sound of the Platine Verdier.
Did I ?
My comment was about a construction feature of the Platine Verdier which was used in this turntable indeed for the very first time in this particular context.
BTW - I have listened to about every commercial turntable released on the market the past 32 years (and a few non-commercial TTs too...).
However - you would never read any comment from me regarding sonics about any current market product ever.

Ok, Dertonarm. I'm just wondering what you meant when you posted this.

The only turntable so far which did it right (i.e. - correct application of "friction" to stabilize movement AND to provide additional damping to the platter) is/was the old venerable Platine Verdier in its original form (pre-1992) of bearing (without the ball support).

Nobody else has gotten it right?

Hi Dan_ed, nobody else aside from Jean Constant Verdier did combine these three effects with one very simple device (two magnetic rings of large diameter (in fact former Focal 15" woofer magnets pre-1990 vintage):

- a true eddy current brake on very large diameter to stabilise the movement
(which in fact is not really bearing friction, but acts in that way WITHOUT any noise added).
- vertical bearing elevated by magnetic force.
- further vibration damping on large surface-diameter of turntable platter (underneath) by magnetic force.

That is all I meant.
I have yet to see another turntable offering these three technical aspects with one simple design feature.
The thread was about bearing friction being applied to stabilize movement. Not comparing turntables regarding their "sound".
Here is one TT doing this AND combining the measure to achive some very nice side-effects.
I am certainly not going into any discussion about sonic pros or cons on this or that turntable.
I would be fruitless anyway.
This is - as always in audio - a subjective field alltogether.
My comment is about unique technical features being combined.
In no way do I want to promote the Platine Verdier here (especially so, as the current model no longer do indeed feature these 3 merits in the way the vintage model does).
There are several TT designs with good points and decent performance around.
All have their merits - all have their flaws.
Thats all.

Dertonarm, Are you saying that the vertical magnetic suspension of the La Platine per se simultaneously offered a form of eddy current braking of the rotation of the platter in the horizontal plane? If so, why would that not also be a feature of the current version of the La Platine? (I am going to check my physics books to verify that such a phenomenon would occur, but for now I accept the principle, if that's what you meant.)