Direct drive vs belt vs rim vs idler arm

Dover, This is what I fear as I grow older: "continuous shrinkage". If you can help me avoid that, please do send the relevant information.

Oh yes, I meant to add that the gibberish you (Dover) quote from the NVS website does not really tell us for sure whether it uses a servo mechanism. Could be that they are talking about the ways in which they assure the synchronicity of an AC synchronous motor controller, to compensate for drag of any kind, stylus or otherwise. I had read from another source that they don't, in fact, use a servo.

The difference, in my mind at least, would be that a sophisticated controller for an AC synchronous motor (which may be what NVS does) would affect the motor's ability to sense that it had been slowed or pulled out of AC synch by some external force and correct for that. Whereas, a servo would require a speed sensor at the platter end that would tell the motor that the platter had deviated from the programmed speed. Then the motor fixes that by applying enough torque to overcome whatever new drag had been introduced. Both cases are a form of negative feedback. You might analogize this to the difference between local and global NFB, respectively.

(I don't much care for NFB in my power amplifier.)

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'