Turntable speed measurements for speed accuracy?

Hello,

The problem with speed accuracy in many turntables, as I see it, is that far too many of them depend upon mains current as their sole power source. If a turntable has a precision power supply, then speed control is addressed by default. In my opinion, a turntable's primary tasks are to spin a record accurately, and spin it quietly. Do that, and you are halfway home.

Regards,
Win

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What is widely done and extremely misleading, is to report the accuracy of the chip used. This information is provided by the manufacturer of the chip and really has no correlation with the turntable's actual speed accuracy.

Agreed. There's some correlation but it's hardly conclusive or adequate information.

It's just as inaccurate to report on the speed accuracy of the motor itself. Speed accuracy at the platter is the goal, and it's easily affected by stylus drag. Measuring or quoting specs anywhere but at the platter with the stylus in a modulated groove has little meaning.

If a turntable has a precision power supply, then speed control is addressed by default.

I disagree. A precise source of power is certainly essential, but it isn't sufficient. Power must be converted from electrical to mechanical energy by the motor, wherein many opportunities for inaccuracy reside. Even if the motor does that job perfectly (and no motor does) that mechanical energy must be transmitted to the platter without loss or inaccuracy, another opportunity for errors. Finally, the entire system must be able to overcome the variable load of stylus drag whilst playing real records, an extremely difficult engineering problem.

I agree it's vital, but maintaining constant and accurate platter speed under variable load is a terribly complex problem, and no set of wow and flutter measurements will come anywhere close to identifying how good a particular rig really is in this respect.

Doug,

I agree completely. My answer was simplistic, so that's why I said "halfway there" in my post. There are so many relationships to consider that it is mind boggling. I suppose the real test comes when the stylus hits the record in the presence of experienced, but unbiased listeners.

Regards,
Win

Doug : "Finally, the entire system must be able to overcome the variable load of stylus drag whilst playing real records, an extremely difficult engineering problem. "

There is a name for this, it's called mechanical coupling. I think you are overstating the difficulty of achieving tight coupling, it isn't hard at all as anyone with an idler table can attest.

The difficulty has been getting a motor that runs on speed which is quiet enough to be used when tightly coupled. That difficulty is slowly being addressed through several avenues, some of which haven't reached the market yet.

Mark,

Thanks for the clarity. It is possible to achieve speed stability, as you most certainly know. Still, it is a game of fine tuning that I suppose will always continue to progress. The best we can hope for is a result that doesn't hamper music, and that, like Doug says, is easier said than done.

Regards,
Win

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