Direct drive vs belt vs rim vs idler arm

What a great thread! I tune out for a couple of weeks and almost miss the best thread in ages.
Halcro: Here are the results from my DIY dd turntable. I used the motor and electronics from a Revox B790 which is based on the dual eds but with more sophisticated electronics with a platter from a feickert tt. https://picasaweb.google.com/114629926159017275364/MyPictures?authkey=Gv1sRgCLqX-P6Iw6SUdA#
Hope the link works.
Your results for the tt101 are interesting but more telling (as you have multiple arms) would be to place the smaller feickert test disc on top of a (heavily modulated?) 12" lp and play the lp with one arm and the test disc with another. This will give us a picture of what's going on in real time under dynamic conditions.
I proposed this a while ago on the tt speed accuracy thread.

Halcro. Thanks ... will have another look at your results. I've read about the Dual eds motors and have long contemplated a DIY using one of these. I still have a couple of these so the next project will involve using one of these motors. I managed to pick up a cosmetically trashed Revox B790 with a broken arm so scavenged all the working bits. The motor looks to be based on the dual with an identical upper casting but the electronics are much more complex and use quartz locking. I replaced the thrust pad and changed all the capacitors on the boards and housed the power transformer in an outboard enclosure ... no other mods except for the platter. I picked up an acrylic Feickert platter with brass inserts on German eBay and decided to chance using it as it is MUCH heavier than the Revox one. Decided to use acrylic for the plinth as I had a Basis Vector and figured that tonearm had been voiced on acrylic. I have used it over 6 months now with no problems. I pulled it apart a couple of months ago and the bearing seems to be holding up so far. I'm very happy with how the tt sounds.

Tonywinsc, thanks for your comments. As far as centering the record goes, I didn't do anything so I think I'm just lucky to have one with a reasonably well centered hole. When I did the test I was actually at first disappointed. as the pitch waver was still quite audible. Goes to show while we debate the minutiae of 0.008 % speed errors the record itself is much more to blame for wavering pitch than most good tt's regardless of drive system. Halcro, when I made my tt , the fact that I used a much much heavier platter than the Revox tt it came from caused some anguish but have had no real issues in practice , the tt comes up to speed quickly and seems to hold speed pretty well even if I use a record brush. I still need to somehow rig up a second arm and do the test I proposed in my previous post to see what happens when playing music just to make sure the servo isn't going crazy with the added mass. Finally , I apologize if my posts come up in the wrong spots in the thread as the powers that be took almost 24 hours to put up my previous post.

My posts are not in sync as moderators are really taking their time . My last posts took something like 20hrs to come up. Seems the A'gon forum is run with a degree of paranoia that is just unbelievable...... I don't how I can take part in a meaningful discussion with such a long delay. ...... so frustrating. Anyway now that I've had my rant I think Tonywinsc hit the nail on the head when he said that our turntables are holding speed an order of magnitude better than the capability of the records. As I said the pitch waver from my supposedly well centered test record was easily heard. Even my belt drive tt while not quite as good as the dd was quite good compared to error caused by disc eccentricity . Halcro & Richardkrebs wrt worse results from tests of longer duration, could it be the stylus heating up when playing for a longer period and perhaps increasing the amount of friction which in turn might be throwing the servo out ?? Just speculating, in reality I have no idea.

"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.