I am with you with you anti-servo prejudgeses. The moment from motor, regardless if it is strong or now weak, should be constant. At the very moment when the moment changes it’s value the platter performs a microscopic “move” in it’s bearing. So the forcing moment and the force of slipping in belt or on a roll should be very constant – juts stabilize the voltage and let it to spin as is.

BTW, I very much like how Micro did it this big TT. They have a moron run for a first few seconds in servo mode, just enough to push the platter from stationary position then the servo was shut and the motor/platter tandem are spinning linearly.

Somebody have asked in this thread - where is the necessary limit of stability and compare the low numbers of platter stability with low number of distortions. I do not think that it is a correct comprising. Anyhow, I feel that the stability of platter should be low-enough in order a listener juts not to hear tone variation. It should not be better…

Not one to fix too firmly on a given implementation, I rdecided to futz around with my vacuum holddown this weekend.

The power was not very good, but I was none the less able to determine conclusively that [within the context of my rig] although the sound certainly benefits from the vacuum (as opposed to no vacuum), there is such a thing as too much vacuum suction, which, past a critical point, begins to vacuum away ambience, where it would otherwise be part of the program, and likewise bass harmonics suffer when I overdo the vacuum.

I do not conclude from this that a lesser LP-to-platter coupling is better, because I am not certain if the coupling is wholly directly proportional to the vacuum, or perhaps there are other factors at work having to do with reflections, or new transmission paths, or vacuum leaks, or whatever.  Certainly this phenomenon could be peculiar to my TT - as opposed to all vacuum HD rigs - but even if this is the case I find it interesting.

Anyway, just in the interest of science (in its humorous guise).

I was also thinking some more about speed control and wondering about the "perfect platter bearing", whether it would indeed be friction free or perhaps it should acyually have a certain controlled viscocity/drag, in order to offset motor stepping?  I wonder if in practical terms a quite heavy platter with no perceptable drag would overcome motor cogging and related belt response?  In the case of less-than-very-heavy platters I suspect that some sort of damped "drag" might be a good thing, and perhaps best applied at the spindle as "oil", maybe multi-viscocity oil.

Lastly, if a "fully-levitated platter" is already 100 lbs. of - say - lead, then why should it have a "ground"?  Why not just let it serve as a sink all by itself?

Paul S

Sounds like a Tesla turbine.

jh

Actually I was more thinking about skin friction drag. Did you throw the stones to slide off the water? All that is necessary is speed of rotation of this thing…

http://en.wikipedia.org/wiki/Skin_friction

In fact if this thing reaches own cruse high-speed rotation then the vertical bearing might be even dropped as it would hold itself strictly vertically under the principles of angular momentum. It is similar to the old sea navigation systems that maintained orientation in gimbals…

The Swiss company Da-Vinci Audio that use to make very interesting LC phonocorrector it looks like trying to hit the jackpot with TT design. I look at all the TT that are being made I never stop wondering what the ultimate from my point of view shape of Micro Seiki 8000 never was embraced by other companies. The way how Micro did the bases was the simples possible and that allow putting in the same footprint max among of arms with unlimited design, since the arm-boards allowed spinning on their pivots. Well, it looks like the Da-Vinci has gone there:

http://www.da-vinci-audio.com/Turntable/reference_turntable.htm

They use a heavy platter with vertical magnetic bearing. The same design only with this older model according to them was 100kg – it already a solid mass. I hated their older design - it is what people do for stupid visual appeal instead of the best implementation of the functionality. The new design, it looks like it is a prototype right now is very good and it should make a TT that is very convenient to deal with. I hope then will make it with a reasonable price and I hope it will sound well. Yep, the reasonable price it is exactly what should be expected from Swiss manufactures and this US distributors!

The only criticism that I would express about the new Da-Vinci TT idea is that they allow only 2 pivots for armbords – it should be 3 as there is one extra space that is not being used. In the rest I applaud the direction the Da-Vinci Audio has gone with this new TT objectives.

I still feel that there was nothing more elegant in the disc/platter interface invented then the negative curve and all those vacuum or “no-vacuum” solutions are half-ass solutions. The negative curving is longer to engage but it takes time until vacuum builds up as well….

I would personally discard the whole subject, as I do now, and would play the records without forcing them to do anything then just freely lay atom of platter. But I am a freak in it as I do not like even the records camps. I have camp but I hardly ever use it….

Romy, what do you mean by "the negative curving is longer to engage"?  I picture a platter that has been machined to the negative trace of the LP face but without any means to "engage" the LP unless there are further stipultions, such as weights, clamps or vacuum; in other words, the negative trace itself is just a "mirror" resting place where the disc sits +/- , according to how flat it happens to be, unless and until the disc is made to conform and sit perfectly tight by other means.  Of course Micro did have high-tech vaccuum TTs available, too, although I know nothing about them, nor do I know anything about their propritary clamps, if they had them.

It appears however that I am the oddball, with the vacuum, since the vast bulk of TTs are sold and used without any means, let alone any effective means, to couple the LP to the platter, negative curve or no, and most people who use the clamps believe they are just flattening the warped LP with them.  While many people want to think they are coupled, most of that lot basically does nothing active to ensure that it happens.

If anyone following along has used low-pressure vacuum for a while and then gone away from it, please speak up and offer some intelligent reasons for your switch.  Although Lloyd Walker makes some very interesting observations during his clamp versus vacuum arguments, the "tap test" and subsequent listening comparisons have convinced me of the generic fact that well-done coupling is very beneficial.  In my comparisons I hear no advantages in loose discs.  Needless to say I am curious to hear the Walker, although it could be pretty scary, given the ancillary equipment they all seem to use.  Even so, as I laid out in my "Balls to Shop" thread, there might still be some There there.

Best regards,
Paul S

Paul S wrote:

Romy, what do you mean by "the negative curving is longer to engage"?

Paul S wrote:

Although Lloyd Walker makes some very interesting observations during his clamp versus vacuum arguments, the "tap test" and subsequent listening comparisons have convinced me of the generic fact that well-done coupling is very beneficial.  In my comparisons I hear no advantages in loose discs.  Needless to say I am curious to hear the Walker, although it could be pretty scary, given the ancillary equipment they all seem to use.

I am NOT a big fan of Lloyd Walker, I do not pay a lot of attention to what he says and I genially am not happy with what he does or willing to do.