Turntable speed accuracy

I agree with Dertonarm on this subject. DD turntables vary due to their designs and construction. Some are very accurate. String drives can indeed be very accurate, as long as the string is fresh. Idler drives, the one I know a little about, have an inherent tracking error of around one part per million, depending on the footprint of the idler wheel itself. Belt drives are not so inherently accurate as the others, although advances have been made to alleviate belt creep through various workarounds and, of course, the recent use of tape.

So, a controller should be pretty accurate, but exactly how much? I believe one part per million accuracy is reasonable, but if we do that, we can easily substitute a standard clock with an OCXO (oven controlled quartz oscillator) with GPS referencing, which can improve the accuracy of a properly designed controller to around one part per trillion, or better. Can anyone hear the difference with such a controller connected to a turntable that is only capable of one part per million accuracy due to mechanical constraints? Certainly, the math doesn't warrant the extra effort, but at least all bases are covered. Would such an accurate controller be warranted with a proper string driven table? I don't know, but virtually anyone can hear a measurable difference with a good controller. That much I do know. If you have the opportunity to compare a turntable without a controller to the same setup, but with a good controller attached, listen for little parts of music that we never typically use as a guide, like small sounds from background reed instruments. You might be surprised.

Win

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A point was stumbled upon here, but no one followed through with the observation.

Halcro noted, "...you would have seen.......about half way through the video......where he drops the cartridge on the record and immediately.....the speed decreases?
And this is only the beginning of the record. Not a heavily modulated passage?
Can you imagine what happens with a really heavily modulated passage? And that turntable in the video has a very heavy platter."

Of interest to me isn't that the speed controller, assuming there was one, is inaccurate. It may be perfectly designed; we don't know. So, what basic principle would cause the speed drop? It isn't electronics, so it must be mechanical. If that is the case, all the electronics in the world cannot fix a fault because of a faulty design in the parts that make the turntable. My point is that inertia has to be addressed at the outset of a turntable's design, and that electronic speed control merely augments it. I strongly believe that 100% success is not found unless the all the pieces work in unison.

Sure, you can improve a turntable by adding an electronic speed control. The true nature of the recording is best exemplified when inertia is a major consideration to the basic design, in my honest opinion.

"Mosin, as inertia is directly related to mass and friction.....are you saying that heavy platters have inherently greater inertia than light ones?"

What I'm saying is that sheer mass is less effective when it is capriciously used than when it is purposefully assigned to achieve an optimum moment of inertia. As far as mass on a platter, I feel that its benefit as an isolation component is another key reason to use it.

Of course, there are more ways than one to skin the proverbial cat, so lighter platters may also work with some designs. I work solely in the arena of idler drives, so that is where I spend my time looking at such things. Recipes vary, but the performance depends on the entity as a whole, and not just a single part because every part is critical to the outcome. Any shortcut is a compromise. At least, that's what I have come to believe.