Direct drive vs belt vs rim vs idler arm

Lewm,

According to the Stereophile Review of the Wave Kinetics NVS it uses a DC motor with a laboratory grade servo controller with an active ultrasonic feedback loop

Reference - Stereophile vol 35 no 10.

"Ultrasonic". I don't doubt you for one minute, but WTF does "ultrasonic" mean in this context? Stereophile reviewers are notorious (in my mind anyway) for uncritically re-stating just about any pile of BS given to them by the manufacturer of a product under review. Sometimes the verbiage in the review is taken right off the manufacturer's website or sales brochure. But in this case, none of that would matter, as the only issue is servo or no servo.

I could have sworn that one way in which NVS claimed superiority over the "old guard" DD turntables (e.g., Technics) was that they had eschewed the use of a servo mechanism. I thought that was mentioned in that thread on NVS that eventually got deleted from this website. I must be incorrect.

'Ultrasonic' They are possibly referring to the speed measuring sample rate. It is a long time since I looked at the Goldmund speed sensor, but from memory, it was around 34,000 samples per revolution. This is not an unusually high number for a speed sensor. If you want to call this an audio signal, which it isn't, it would be almost ' ultrasonic'

Re the Goldmund Speed Correction
Given that the GP Monaco checks the speed 7200 times per revolution using current computer technology and software, I would vey much doubt the number quoted in the previous post ( 34000 per revolution ) for a 30 year old DD.

Dear Dover, You are probably correct, and the discrepancy is probably one of semantic nature. Maybe the Goldmund spec is "per minute", for example. That would make the GP Monaco much faster than the Goldmund, which we agree it should be.

But I do take the point, which I myself realized after posting, that the term ultrasonic must mean that the correction rate exceeds the highest frequency of what we deem to be the audio spectrum, 20kHz.

As to servo or no servo in the NVS, I went to their website, Dover, after you quoted from it. In fact, I do not see the word "servo" anywhere. Did I miss it?