Direct drive vs belt vs rim vs idler arm

I guess the propensity to assign cause and effect without data to connect the two is inherent in human nature. This is why we have... religion. Because one knows there is a servo in action, and because one hears a coloration - this is not enough information to say that the servo causes said coloration. I think I know what coloration it is you are talking about vis the SP10 Mk2; I heard it too. I found that it can be ameliorated or aggravated by the choice of plinth. So, how could the choice of plinth influence servo action? Maybe there is a way that could happen, but one has to test it before jumping to conclusions about cause and effect. Plus, we have the (correct) testimony of Richard that the servo does not operate like a full "on", full "off" switch, which might indeed lead to a kind of incoherency. The servo is more sophisticated than you (and certainly Dover) think. Yet despite what Richard wrote a few weeks ago, we have reverted to talking about servo mechanisms as if they are nothing more than on/off switches.

What about the latest megabuck DD turntables? I think the one from the Northwest (NVS) does not use servo correction. Is it free of the sort of coloration we are talking about? Rumor has it that it does not pass the Timeline test. The carbon fiber Grand Prix Audio Monaco uses a very advanced mega-fast modern state of the art speed correction system, yet it is not widely loved. Why is the SP10 Mk3 very much more natural sounding to my ears compared to the Mk2, if this is only about servo problems? (I don't imagine there are major differences in servo design between the two, but maybe.)

Not picking on you Dover but you talk about digitized sound from DD motors because of there electronics..but you dismiss the FACT that your Final vinyl TT uses some kind of sine wave generator so it does not rely on the line freq stability but hmmmm lets see what kinda electronics could or would they imply in practice?! Quartz oscillator? feed back?! etc. you get the point..lot more to understand before we/YOU can come to a "more better" conclusion

kind regards

Lawrence
Fidelity Forward

Lewm, Lawrence
Could I ask you respectfully to reread my post.

My post addresses some points made in earlier posts about "motor slip" and "speed correction systems/servos", both of which can be present in any type of turntable or motor.

AC motors have been used in Belt Drive,Direct Drive & Idler
DC motors have been used in Belt Drive,Direct Drive & Idler
Furthermore there are many variants of both AC & DC motors.

Speed correction systems have been used in both Belt Drive and Direct Drive.
Speed correction systems have been used in both AC & DC motor applications.

I use those particular TT's mentioned as examples because I know them and know what type of motor they use.

Ct0517 wanted to know more about speed controllers & servos.

My post tries to explain that most speed correction feedback loops would include the following parameters - Rise Time, Overshoot, Settling Time, Steady state error, Stability - and any solution has to be a compromise between these parameters.

The question is " Do the issues inherent in speed correction/servo loops outweigh the benefits ? "
The correct answer is "We dont know".
Why ?
Because nobody has quantified the error versus the errors generated in correcting the error.

Tonywinsc,

In answer to your question, it's my opinion that it could be any of those things you mention. If I heard it, I might be able to tell, but it's impossible to say from here. It is too bad you don't have the luxury of trying several tables, arms, etc. in your system. Then, you might be able to make a determination. It could be the record, you know?

What about the latest megabuck DD turntables? I think the one from the Northwest (NVS) does not use servo correction. Is it free of the sort of coloration we are talking about? Rumor has it that it does not pass the Timeline test.

From the Wave Kinetics website
Speed Control
Capable of both 33 1/3 and 45 RPM
Utilizes a laboratory grade motor control system
High inertia platter
Speed accuracy to 1 part per 1000000
Direct drive system
Tuning optimized using a 17 degree of freedom tuning model

In linear regression the degrees of freedom is the number of estimated predictors. Degrees of freedom is often used to quantify the model complexity of a statistical modeling procedure.
This tells me that they have sophisticated speed control programmed into their speed controller based on the prediction of errors ( see my post of 02-02-13 where I explained how the algorithms are derived ).

17 degrees of freedom does not mean 17 parameters either - I can send you the linear regression mathematics behind this statement if you like.
It tends to suggest that their programs are using statistical analysis, and a continuous shrinkage technique to improve the prediction of error on the fly.
In other words, the input parameters for the speed correction/servos are not set in concrete, as in the old days, they are calculated on the fly.

As suggested in my earlier comments on the age of the Technics SP10 circuitry, these folk are using much greater computer power and new thinking on statistical prediction that is now available.

Caveat : Just so everyone is clear - I make no comment on how this turntable might sound and I am ambivalent as to the drive mechanism used.