Direct Drive vs. Idler Drive vs. Belt drive

Mike.

Many thanks for the invite. There is a little problem of distance however, since I live in New Zealand.

I do not disagree with you at all re the signature of "most" DDs. I spent 15 years whittling away at my mk3, little by little mitigating the very signature you describe. This journey started back in the mid 80's when this trait in my Sp10 mk3 was, to me, obvious  Note I did not say that I totally eliminated it. Still, I really liked the good things it did, does.  

More recently, I was approached to build a ground up TT. The options were ID or DD, I chose DD. I was given total license to do what ever I wanted. This was an opportunity to apply all that I have learnt in my professional life and in this hobby and someone else was offering to pay for it. I said to myself " How hard can it be?'.....Well that turned out to be a very naïve question.

The project took five and a half years, with 1000 hours of that time ( six months, 8 hours a day, equivalent) devoted to programming the controller. There are literally thousands of setting options and many of them interact with others.  We were making changes to the speed stability in the order of 0.001% and we could hear them. We were actually changing the 'shape' of the W&F. As I have said in this thread, it is really hard to get a DD to sound right. But I do not consider it to be impossible. Time will tell if others agree with me, I'm fine with their opinions either way. This is inherently a subjective hobby  

Servo controllers get a bad wrap in these and other parts. Yet most of us are listening to systems where amplifiers are using feed back and we do not think twice about this. A servo controller is a form of (electro-mechanical) feedback. Its application is a bit like Goldilocks and the three bears. Too hot, too cold or just right.  

Another thing which many DD owners like to demonstrate is the long term speed accuracy. Watching a stationary laser dot on a distant wall. This is touted as a virtue and proves the superiority of DD over all other drives. I do not agree, and do not claim to be able to hear the difference between a constant 33.334 and 33.332 rpm. My design doesn't concentrate on this metric.  What, to me, is important is the speed accuracy at a micro level. How speed stable is the drive under dynamic load, between a few arc seconds of rotation and the next set.  Firing of a shot of red light once every 1.8 seconds does not tell you jot about what is happening at this microscopic level. 

Cheers 

Well said Richard. Wow and flutter after a point are more noticeable than absolute speed. That point it seems to me is 0.1%. Under this it is inaudible. Speed wandering is always a problem if it occurs rather quickly. Quickly enough to hear a pitch change during a side. 
A significant reason for varying opinions is that all of our experiences are anecdotal. None of us has listen to a large panel of every type of turntable under controlled circumstances. I do not like DD turntables because all the ones I have listened to in situations where I have been able to compare them directly to belt drive tables have not done well. So, in my experience DD tables are not good. But I can't accurately say all DD turntables are bad. There may be some new designs Like Mike's that may be fine. I am also talking about tables over $10K . 
As Richard says this is mostly a subjective hobby and unless we go out of our way to be objective (which is very hard to do) our subjectivity only applies to ourselves. Therein lies the danger of giving and taking advice as to what and what does not sound good or better. 
Geoffkait, I have to agree. The dynamic compression used on many CDs is disgusting. But, there are high res downloads that are incredible. Recent examples are the Punch Brothers, All Ashore and Brittany Howard's, Jaime. 
Lewm, I have a bunch of re mastered Miles stuff on modern Prestige pressings, many of them mono that are excellent.
Lastly, everyone should take a look at Reed's 5T tonearm. What a brilliant design. I do want one of those!

I have a chance of going for a bespoke high quality replacement for the tt speed controller on my Salvation direct rim drive tt. It'll be a total punt in that I'll be buying a custom order device w no chance of hearing it. The designer is long term user of my tt/arm, and uses a Clearaudio Goldfinger (that should appeal to Mike), and so if he feels it passes muster, I'll buy w some confidence.
Part of the Salvation's magic is that it doesn't use any servo feedback/loop at all. Indeed, whenever designer Vic tried to incorporate it, either an optical encoder or a voltage fluctuation gauge, the sound became colder, grainier and less compelling.
Vic's existing stock tt speed controller is pure analog, set by reference to speed strobe, but is not particularly bulletproof. The bespoke replacement will have way better component count and a couple of features that make it pretty unique. And I believe, no servo feedback while lps playing.

It is weird that people on this forum are not familiar with EMT 950 and 948 DD turntables.
They work different compared to Technics SP10 mk2 and mk3.
EMT DD have a powerful DC motor and lightweight platter. IMHO it is much more proper servo control design.
EMT DD were very expensive in 70x, 80x. 950 costed 15000DM.
A number of times more expensive than Technics SP10.
And they where sold on professional market before marketing era.
That days, studios and radio stations knew what they pay for. Not like modern audiophiles pay for a piece of a modern art design.
I also knew that Japanese audio enthusiasts prefer EMT DD turntable to their local stuff. A big part of EMT turntables where sold from Germany to Japan.