Direct drive vs belt vs rim vs idler arm

Lewm cc Richardkrebs
I dont think the Goldmund numbers quoted are indicative of the sampling rate. I dont think you can count the number of wavy lines on a pcb and equate this to sampling rates. The Goldmund uses a coreless JVC motor. It uses a quartz lock servo. It is more likely that the wavy lines on the circuit board are used to generate a phase signal that is compared to a reference in a feedback circuit. The loop bandwidth of the feedback circuit determines the speed of the feedback loop.
It would be more illuminating if Richardkrebs actually explained what type of motor the Goldmund uses, how its speed correction works and why he chose to abandon the TT self build project with this motor.

the Studio's JVC motor was a good implementation, but the motor was unsophisticated.

"So, Richard, are you inferring that the GP Monaco claims for the speed of their speed correction system are not so earth-shattering or envelope-pushing as one was led to believe, given what Goldmund did two decades earlier?"

Goldmund didn't do it at all! They just sourced the motor and electronics....first from Papst then from JVC when the Papst motor was discontinued. Their claim to fame was the use of methacrylate and in the energy transfer path to drain away vibrations... I do the pink Triangle predated their use of acrylic (and maybe Merrill as well).
IMHO neither Goldmund nor Monaco would have the resources to pull off a dd system in the way one of the Japanese giants would have back in vinyl's heyday.

Dover.
Are we not getting off topic here? My reasons for dropping the Goldmund motor as a mule for my TT project will in no way advance this thread. It is an average motor with an above average speed measuring mechanism. Further you have described how it works. I only used it by way of example to back up my earlier assertion that high sample rates were used way back then. You are quite right, the sample rate and feedback loop bandwidth of two different things. It is probable that the samples are put thru several divider networks to bring the sample frequency down to a manageable level while simultaenously improving accuracy. (Other TT's of that era do this). I no longer have a circuit diagram so cannot confirm.
And yes, wavy lines on a PCB under a multi pole rotating magnet are one way of measuring speed. Their output count is exactly as I described. Still used today in our industry for their robustness and long term reliability.

02-11-13: Richardkrebs
Dover.
Are we not getting off topic here?

No. Read the name of the thread.