Direct drive vs belt vs rim vs idler arm

Dover recently I had a demonstration of a Nakamichi 1000 table and was impressed, I just got caught up in the hoopla about it thats all,I should read this site more and I'll shut up .I know a reference position is needed of course to use a centre correcting jig and much more work can be done on my attempts.
Mosin I agree with Lewm on the issue of direct drives, Halcros nude thread on plinth-less dd is a shining example of the influence poor plinth design and material used can directly effect performance. On the other side of the coin is the plinth of the fantastic Kenwood L07D.

Lawrence,
even if this is the case as you described very well with the Lenco users this is not an argument against idler drives per se. Not all horn systems have a limited bandwith. I am a running a perfectly adjusted EMT R 80 idler with my modern 5way horn system (TAD berrylium drivers) with two active subs and I am pretty sure there is no limitation at all. I am able to compare all three drive technologies in one system. As said before in the Top League it is more a matter of implementation than what kind of drive you are going for.

Ketchup
I will take your figure as correct. I did the calcs long hand while waiting in a Cafe for a Flat White ( that's a coffee to those from the Northern Hemisphere)
Yes the number is small and if you extend the distance out further, which we are all quite capable of decerning, the L/R delta gets smaller. Quite amazing.

Dover The jitter artefact, as Mosin quite correctly points out, is not limited to the Technics line, he hears it in DDs in general. Actually my testing and listening has shown it to be present in any motor that uses feedback be it local feedback ( self correction) as in free running motors like those in most BDs / idler drives or global feedback as in DDs. That is it occurs in all motors. Since all TTs have motors ......
I hasten to add that this is definitely not cogging, it occurs at frequencies above that which the physical motor build would precipitate cogging.
It occurs at a higher frequency still in DDs, where global feedback is employed and is more obvious in higher torque motors, but it is there in all drive iterations.

01-28-13: Richardkrebs
Dover The jitter artefact, as Mosin quite correctly points out, is not limited to the Technics line, he hears it in DDs in general.
Actually my testing and listening has shown it to be present in any motor that uses feedback be it local feedback ( self correction) as in free running motors like those in most BDs / idler drives or global feedback as in DDs. That is it occurs in all motors. Since all TTs have motors ......

Hi Richard/Mosin

Looking to learn and substantiate what I hear.

Can you please describe the feedback you are “hearing”

Differences in sound between local and global feedback ?

Thanks

Ct0517.
In my view both types of feedback have a distinct sound in their "as built" states. Firstly I need to state two things.
1) I have a commercial interest in this topic, so you may want to take that into consideration.
2) How a machine is designed and how it is built are often completely different things. The designer makes a number of assumptions on the motor and feedback performance. Commercial reality can get in the way of these assumptions being realised.

This is what I hear.
Global feedback when carefully designed, but not properly put together, creates a tension in the music, a greyness. The music does not flow and does not properly connect with the listener. It is not servo overshoot, hunting or cogging. This sound is what the BD people talk about. This problem, in my opinion, can be largely removed.

Local feedback is softer and slower to respond to demand, it creates a slurring effect. The music is slightly blurred like a soft focus lens. Drive and dynamics are diminished.
My research into motors has shown that this can be reduced only slightly. The method of coupling the motor to the platter is immaterial, as this effect is built into the motor itself. This is why I have pushed my view that global feedback is neccessary, regardless of the drive method employed. It is the reduced "drive" that the DD people talk about.

Of the two, if I had to choose, I would take local. That was before I found a way to mitigate the problems of global feedback.

I hope that this helps.