Calling all analog experts

A general comment from an engineer with long experience in the design and testing of precision servo loops..

If you want to maintain precise uniformity of mechanical motion (such as RPM of a turntable) in spite of variable drag and/or motor torque, there are at least two ways to approach it.

The old fashoned way would be to use a massive (heavy) turntable/flywheel. Variations of torque, either due to drag variability or motor torque fluctuation will be very slow to change the RPM, and since these torque fluctuations a very brief, the RPM change is very small.

The modern way would be to use a very lightweight turntable/flywheel driven by a powerful computer-controlled motor. The motor, under control of the computer, applies the torque that, with the old approach would have been generated by flywheel inertia. In fact, the computer could simulate a flywheel much heavier than any real turntable. This approach needs a lightweight table so that its inertia doesn't "get in the way" of what the computer and motor are trying to do.

I really don't know if anyone has found it worthwhile to design a turntable using the latest technology (the market is very small) but I would warn anyone with a direct drive turntable that adding turntable mass may degrade rather than improve speed stability.

Same goes for adding extra capacitors to a regulated power supply.

Eldartford: While I gladly will acknowledge your level of technical knowledge, I must ask you what relevance does your last post have to my original topic? I'm sure you have an opinion that could be useful in this matter.

Doug, Caterham, Sayas, Eldartford and Jsonic,
I would reiterate my willingness (and I think Doug's) to host a comparison of the alteratives (e.g. my lower cost Michell Gyro, vs, Doug's "ultimate in analog" Teres) (P.S. Doug if we arrange it at your place I'll provide the "refreshments") Send notice by private email if you have an interest and perhaps we can set something up.

Jsonic, you should be glad we've turned this discussion into a real, serious one looking at TT design parameters and constraints. If you search the archives you'll see it over and over--people just parroting away belt drive choices without any real technical considerations--especially in the lower price range, where *glass and particle board* TTs abound.

From this thread it is evident that there are two choices in your price range: Teres (belt drive) or the KAB modded Technics SL-1200MKII (quartz-locked direct drive). I chose the creature on steroids and am very glad I did. I am getting phenomenal performance on a real world budget--and will keep getting better as I do some more tweaks to the power delivery and have the tonearm rewired and new interconnects. I just love direct drives. They're for people who want to *play* records. Here's some input from the owner of Bear Labs, who owns a top of the line Denon DD:

You just discovered several of the the advantages of Direct Drive 'tables!

In order to make an informed choice you MUST listen to a high quality direct drive unit, be it a Technics, Denon, Micro Seiki, Goldmund, Rockport.

Jasonic...These threads do tend to evolve into discussions related to, but not directly answering the original question. Frankly, we often answer one of the prior posters, rather than the original thread author. In this case Dougdeacon's mention of me by name, referring to a prior discussion, caught my eye. Sorry to confuse the issue.

Regarding the particular units that you have under consideration I claim no expertese. To put it bluntly, I am very well served by my high tech but definitely non-approved by audiophiles Sony ps X800, and have, for some years invested money elsewhere in the system. I follow TT technology just for the interesting ideas involved: not with the idea of buying a new TT.