Direct drive vs belt vs rim vs idler arm

'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?

Have just pulled apart an old Goldmund motor I have lying around.
I am impressed all over again with its speed sensing design.

It has 164 slotts and 176 magnetic poles ( north plus south) in the speed sensor assembly, per revolution.

This gives 14,432 counts if they only consider, say, north pluses and 28,864 if they use both north and south. My memory was a little out. Apologies

Didn't Goldmund use the JVC/Victor motors?