Turntable speed accuracy

Unoear ask:

why do you think that the NVS was not up to task? ... It appears that is not an issue with the quality of the mains being presented to the motor controller; otherwise, I guess that Technics Mk3 would also have an issue...what do you think could be the issue with the NVS?

So far no turntable has passed the test as I conducted it, except the MK3. The NVS was up to the task as the rest.

Have you checked your DD Rockport?

I have a huge bias in favor of that table. I wish to know if it's as rock solid as I imagine it to be.

Lewm posted:

Albert, EMI picked up by the cartridge from the L07D motor was rumored to be an issue. It seemed improbable to me, because the platter and mat constitute two solid slabs of stainless steel which ought to afford some decent shielding. Nevertheless, I made an LP-size shield out of "TI Shield" (Texas Instruments), the best shield around for a combo of EMI and RFI, and I inserted it over the spindle and in between the platter and platter mat. This actually did result in a noticeable but small increase in transparency even though I heard no "noise" per se prior to installing it. The Mk3 ought not to have any issues in this area, because its thick brass and SS platter is an even better natural shield than is that of the L07D.

I use the TI FerriShield too, although it had no affect in tests with the MK3. With the MK2 the results were astounding, I imagine the holes in the aluminum MK2 platter looked like a strobe light to the phono cartridge.

When I say FerriShield was effective with MK2, this assumes the stock rubber mat, the Funk Firm mat, Boston Carbon Fiber or other mat that offers no blocking from RF and EMI.

Looking back I now realize some of the amazement of the Micro Seiki Cu-180 was the hard surface and superior design, but also the total blocking it provided, equal to the Texas Instruments in my tests.

My current mat is the TTM from Japan and is the highest performance mat so far on my MK3. I suspect it's mass is too much for the MK2 but the MK2 does well with the Micro Seiki Cu-180 and negates the need for FerriShield.

I have not gotten into this much in forums, but the center weight or clamp, plus mat is almost as much affect on sound as tonearm cable (and in some cases) the cartridge itself.

Maybe I'll make up a list of combinations of mats and clamps and what I heard. I sometime wonder if this variable plays a role in cartridge preference among members.

If any of you have tested same, I would love to read your results. I've been doing this for several years, it's a tedious process since one must be VERY careful to insure VTA and other variables are not more result than the parts in play.

Hi Albert,

Yes, the string-driven Big Micro Syntax machine was up to the task and, as I mentioned, spot-on; the Seiki was consistent, rotation after rotation, as represented by hole burning in the wall.

No, I did not get a chance to try a Timeline with Rockport Sirius lll while it was here last year. However; Tim Sheridan, was here late last year for a visit before I shipped the Rockport to its new home...where it joined a few other Rockport TT siblings in the UK. As you may know, Tim is the designer of the motor controller (MDA) for the Sirius lll. He tweaked the MDA to bring the speed accuracy of the Sirius lll back to his standards along with preparing the mains change and a few other items.

Cheers!
Alan

Perhaps the key to the accuracy and consistency of many DD turntables.....is their inbuilt ability to monitor the platter speed against a quartz crystal timing device......and make instant corrections for any deviations?
I don't know of any belt-driven turntables able to do this?.....nor for that matter....any idler decks either?

My experience with belt-driven turntables and the Timeline.....is that one can set the speed controller to be fairly stable with no cartridge playing OR with a cartridge tracking the groove.....but they are two different settings?
The 'stylus drag' slows the actual platter speed.....but as the motor controller does not know this (it is only putting out a constant signal)......there is no compensation?

Alan, have you tested your own Micro Seiki SX-8000 with the Timeline and when you say that Syntax's RX-5000 kept constant accurate speed......did you see this with and without a cartridge in the groove whilst not adjusting the motor controller?

Halcro: "Perhaps the key to the accuracy and consistency of many DD turntables.....is their inbuilt ability to monitor the platter speed against a quartz crystal timing device......and make instant corrections for any deviations."

While I am a fan of direct-drive but I am not sure that's a good thing about servo making "instant corrections for any deviations." Any error has to be detected first before making correction so it's after the fact and sometimes if treating it with an iron fist approach it can cause unnecessary jitters and possibly that sterile sound we associate with DD tables. I think the key to good sound in DD, other than motor quality, is how the designer approaches this servo or corrective system in a sensible way. If the outside disturbance of the speed is too large, I see no need to correct it and just let it be. For example, if I were to tap the platter rim with my palm while spinning and I don't see the need for the platter trying to hold speed. It comes down to how smooth the correction is. I don't think servo response time have to be so quick. A gentle approach is probably more pleasing to the ear than a brute force one. I can be wrong and there are probably good sounding DD tables (TT-101?) out there using the quick fix approach.

I understand stylus drag is not a constant resistive force, neither is music. Perhaps the torque should be set just high enough to plow through the most demanding musical passages (1812, anyone?) and leave it at that so the servo does not have to do tap-dancing all the time? Of course, it's impossible to do instant servo on belt-drive of course due to the elasticity and time delay of the belt but its gentleness probably offers a pleasing sound.

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