2008 RMAF – – – all things analog.

Robdoorack, Thanks for the interesting data. The measurable deviation cited was more than I would have expected. As Doug points out the measurement time period is very significant. Most people are not able to detect relatively large errors in average speed. For the majority of us the threshold is more than 0.1% and nobody can detect a 0.0007% error. However short term deviations are a different matter. It is well documented that digital jitter of 10 picoseconds is audible. That's a short term deviation of 0.000000001%, one billionth of a percent! So it should not surprise us that a short term analog speed deviation 10,000 times greater would be audible.

Wow some interesting reading. The speed issue has been with us from the beginning of vinyl playback right. We all have accepted the fact cause were here. I am in constant adjustment between lps. Observation done with a KAB strobe on top of my center weight as I am able to check when playing a lp. I am tuned to hear pitch changes and thats the reason for the constant checking and tweaking. All of the reasons are known for this yet there is no drive system that will remove our drag problem that i am aware of.

In the end though the sound of vinyl play back is so far superior to digital that i can live with the drag in my hearing. IMO

No pun intended ha.

yet there is no drive system that will remove our drag problem that i am aware of.

hummmmmm.

as far as stylus drag/groove modulation.....i think that the Rockport Sirius III's drive system may solve this issue. you have an pure induction direct drive motor with zero torque ripple, a 55 pound platter, an air bearing, and a servo system (coaxially mounted optical encoder) which samples the speed every .000001 of a second.

the only support i have for my opinion besides the design description is the unique way that the Rockport handles musical peaks to my ears. until one hears it on a familiar Lp it's easy to dismiss the signficance of it.

a side note on the servo; when it is engaged a green LED flashes to red. the servo is never engaged unless the 'floating 250 pound plinth' is bumped or if someone jumps up and down on the floor in front of the tt. once the platter reaches speed it stays there. there is no hunting occuring. stylus drag does not cause the servo to engage on the Sirius III that i have observed. maybe the servo engages without the LED flashing, but i don't think it works that way.

i have a Technics SP-10 Mk2 sitting next to the Rockport which does a very good job on this issue.....but not at the Sirius III level of naturalness and continuousness. of course; there are more differences between the SP-10 and the Sirius besides stylus drag to cause these differences.

there may be other tt's which are able to do this same (stylus drag/continuousness) thing equal or better but i've not heard that.

anyway; stylus drag can be solved.....but it's not easy to do.

Great post Mike. Is there another turntable that might match the Rockport? I don't know but this is an interesting proposition.

Imagine for a moment a turntable with 1.1 tons per CM2 moment of inertia, driving a copper laminated platter that weighs 10KG and starts in 0.25 of a second.

Imagine this same turntable has the second lowest rumble (noise) ever measured in ANY turntable, figures of 98A via (DIN 45 507) and exhibited speed variation of zero (unmeasurable) up to applied forces of 10 KG per CM.

The force required to cause error is the equivalent of 1000 tonearms, all tracking at 2g each. Speed error remains +/- 0.001% and wow and flutter is 0.015% WRMS.

Pretty amazing for a turntable that's now 20 years (+) old. Unfortunately they sell used for $6000.00 and up to $10,000.00 in new condition.

It's the Technics SP10 MK3

Albert,

thanks. and i'm excited to read about the technical merits of the Mk3 drive system. it's all your fault i've dived into these vintage dd tt's.

i'll be shipping my Technics SP-10 Mk3 to Dobbins on Monday so he can work his magic with it. then we'll see how it compares to the Rockport and the Mk2.

are you listening to your Mk3 yet?