Direct drive/rim drive/idler drive vs. belt drive?


O.K. here is one for all the physics majors and engineers.

Does a high mass platter being belt driven offer the same steady inertia/speed as a direct drive or idler drive?
Is the lack of torque in the belt drive motor compensated for by the high mass platter. Object in motion stays in motion etc. Or are there other factors to take into consideration?
I am considering building up a Garrard 301 or Technics SP10, but is it all nonsense about the advantage of torque.
I am aware that the plinths on these tables can make a huge difference, I've got that covered.
My other options would be SME20 or Basis 2500 of Kuzma Stogi Reference etc.
If I have misstated some technical word, please avert your eyes. I don't want a lecture on semantics, I think everyone knows what I mean.
Thanks in advance.
mrmatt
The primary hurdle to jump with belt driven turntables is their inherent belt creep.

It is best described here...
http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=694178&highlight=belt+creep&r=

The first thing to deal with is the torque issue. The thing about high torque idler motors versus low torque belt motors is largely a furphy.

The output torque at the shaft of the Garrard motor is a little under 10 mNm. The output torque at the shaft of the 3W Hurst motor used by VPI is 26 mNm.

The reflected torque at the platter is the shaft torque times the gearing ratio. For the Garrard the gearing ratio is about 48 to 1 so the final torque at the platter is about 440 mNm. For the Hurst motor the gearing ratio is 18 to 1 so the final torque at the platter is 470 mNm.

The "low torque" Hurst thus has more torque than the "high torque" Garrard.

To add insult to injury, the Garrard motor slows by 10% when delivering that torque where the Hurst motor does not slow at all.

Mark Kelly
Oops

I looked at the wrong motor on the Hurst table, the actual motor used by VPI is the lower torque model so the figures are 16mNm at the shaft and 290mNm at the platter respectively.

This would seem to favour the Garrard but only if you find a 10% speed reduction acceptable. If you want the Garrard to slow by a lesser amount (say 1%) the useable torque drops almost proportionally - at 1% the torque is about 1mNm at the shaft, say 50 mNm at the platter.

Mark Kelly
All this technical discussion reminds me of the numbers war in electronics in the 1980s. If we are to believe any of those specifications the Yamaha receiver is a much better performer than a Lamm.

I began with rim drive over 40 years ago and was talked into a belt drive, assured of it's superiority by the Thorens rep himself.

I owned tens of dozens of belt drives and each sounded different but not until I returned to rim drive / direct drive did I get the immediacy and impact that had been missing all these years.

I clump rim drive and (good) direct drive into the same category as both provide similar sound.

Quiddity, I don't know where you heard a Garrard or other rim drive that had such poor speed results, but in a side by side test against three of the finest belt drive tables on earth the Garrard was top or very near.
Albert,

Mark makes the controller for my Saskia idler drive, and I can say firsthand that he looks at things from a critically analytical viewpoint. That said, he owns idlers including the Garrard 301, Commonwealth and others, and he can fix the speed on pretty much anything. Basically, he may be saying that the Garrard needs a good speed control. ;)

Best,
Win

Albert

I measured those results in my lab on a Garrard motor I know is in good working order. I have also measured several other motors used in idlers and found very similar results. Since the results accord with the theoretical results expected from these designs I have no reason to suspect that they are anything but typical.

You are correct in saying that the torque numbers by themselves prove nothing, with one exception: they prove that the argument over motor torque does not provide a key to the sound of an idler table vs belt drive.

That variable being eliminated, we can now ask "what other characteristics of these tables may result in the sound we hear?"

I nominate two for discussion: the very small degree of mechanical creep in the idler transmission and the very high reflected inertia of the typical idler motor. Which is more important? I don't know. Yet.

I have designed a belt drive which has a very, very low level of creep. It is in the process of being built and will be on show at RMAF in the Galibier room if we get it finished in time. I do not expect it to sound like an idler table, I expect it to sound like a belt drive with the belt creep problems removed.

The drive design allows for the addition of a high speed inertial system. I expect that if this system were added the sound would change; it remains to be seen exactly what this change is and whether it is seen as a benefit. The inertial system is still on the drawing board, it will not be at RMAF.

One of the problems is that the "donor table" has inevitably been designed to perform with a different drive system. Accordingly I've asked Thom to audition the drive on his lowest model table on the grounds that this has had the least attention given to optimising the synergy between the drive and the other mechanicals.

Mark Kelly
08-01-09: Quiddity
...the torque numbers by themselves prove ... that the argument over motor torque does not provide a key to the sound of an idler table vs belt drive.

That variable being eliminated, we can now ask "what other characteristics of these tables may result in the sound we hear?"

I nominate two for discussion: the very small degree of mechanical creep in the idler transmission and the very high reflected inertia of the typical idler motor. Which is more important? I don't know. Yet.
I nominate a third: how the drive system reacts to stylus drag. A drive with an elastic belt could stretch and recover when it encounters greater stylus drag from transients, where an idler drive or quartz-regulated DD might power right through them.

After all, there are belt drive enthusiasts who replace their stretchy belts with mylar tape or dental floss.

And VPI offers a rim drive. Reviews I've read consistently praise it for more realistic presentation of transients and rhythm.
Johnny

The net effect of the belt stretch is that it causes creep over the drive pulley, so we are talking about the same thing.

The direct effect which you postulate is reduced by the second order low pass filter formed by the belt / platter combination. The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range.
Mosin

That said, he owns idlers including the Garrard 301, Commonwealth and others, and he can fix the speed on pretty much anything. Basically, he may be saying that the Garrard needs a good speed control. ;)

The Garrard I heard was running on European settings with the Loricraft motor controller. Sounded very good, with strong drive and energy to plow through difficult passages.

Quiddity
I have designed a belt drive which has a very, very low level of creep. It is in the process of being built and will be on show at RMAF in the Galibier room if we get it finished in time. I do not expect it to sound like an idler table, I expect it to sound like a belt drive with the belt creep problems removed.

I can't speak about technology that has not yet been created, I can't even speak about every turntable made as I have not heard them all. I have heard tens of dozens of belt drives and all the things discussed here at Audiogon matter (suspension, belt, arm, cartridge, isolation, etc). but there remains one overall character and that is lack of drive. You have to live with each for awhile to understand. I'm not saying all rim drives are perfect nor all belt drives faulty, I'm saying they tend to exhibit qualities or personality, much like we attribute to tubes versus transistors.
Quiddity
The direct effect which you postulate is reduced by the second order low pass filter formed by the belt / platter combination. The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range.

You want to hear a really strange story? I have two identical Technics SP10 MK3 turntables. One was sent to a tech who is considered to be one of the best in the USA. He replaced all the caps, diodes and rectifiers and upon return (even though it tested the same) it KILLED the table with no upgrades.

There has to be a lot of complicated things going on with "drive" and "speed" of these various tables because the start, stop, accuracy and drive can be drastically improved by things like this upgrade and I don't know if those are even in the parts per million.
Albert,

I may get into trouble here, but I am increasingly convinced that the micro-dynamics of analog playback, in particular, hinge partly on things we have yet to measure. I thought I had built a great turntable, but somehow I inadvertently improved the dynamics of it without trying by implementing a change to make assembly easier. We may have figured out a lot about audio, but I really believe there are still volumes left out there for us to discover. I suppose the goal should be not to know everything, but to not know as little as the competition...assuming it is about competition, and I'm not so sure that that should be the end goal. Me? I'll settle for good sounding no matter where it originates. :)
Albert that's not strange at all when you look at the way Technics implemented their servo drives.

They drive the motor coils with single ended amplifiers using capacitive coupling to block the inevitable DC offset. Any such amplifier is very sensitive to the quality of the coupling cap used because it is in series with the motor coil. If the impedance of the cap increases, as it inevitably will with age, the drive available to the motor drops which will in turn reduce the forward slew rate.

I agree that there are a lot of things going on with the various drive mechanisms. Where we might disagree is with your implication that this means they cannot be adequately analysed. The reason I was dismissive of the parts per million difference due to belt stretch is that the belt creep is around 1000 times larger, so there's no point in worrying about belt stretch - by the time you fix the creep problem the stretch problem is gone as well.

Mark Kelly
I was thinking about the SL1200 series - the SP10s used push pull pairs on a dual rail power supply. Since there is no coupling capacitor it can't be the problem but it is still the case that the amplifier will be sensitive to the quality of its power supply.
I'm not an engineer,but more mass seems like it would sound better on all drive systems as long as its done right.That will put more load on the bearing too.The softer the rubber used for the idler or drive belt will probably make it more quiet also resulting in a nicer table.One thing we must keep in mind is good maintenance.About 35 years ago,I had a nice turntable that was pricey for me. The belt got loose from age,so I took it to a mid to high end dealer to let them change it.I thought I was hearing something that wasn't right.By the time I looked into it,the motor bearing was destroyed from the junk tight rubber band belt the dealer used.Try to learn about your table to keep an eye on things.
Hifitime
y.s.: >>>...the motor bearing was destroyed from the junk tight rubber band belt the dealer used<<<

Now what 'table would that have been, I ask?

To get a belt THAT tight, the motor if it was out-board would simply fall over, or?

BUT, if not out-board --- well that's another story. So before I go on, can we hear about this tt by any chance.
Thanks,
Hi,
having read further through this thread one thing comes to mind: The actual length and shear thickness, mostly width of the belt in use.

Some say that this is of quite some importance and actually kept the belt VERY short (pulley under the platter) and beefy, (not thin, round or square) like the flat belts e.g. SME and Linn use.
Then there is the motor controllers, ‘done over’ a number of times by Linn, and at least once by SME.

Listening to a thin (square) belt of a top Pro-ject table and thin (round) on TransRotor Z3 (sans controller) and then a short (flat) belt with controller on SME gives a pretty clear indication of the difference in transience/attack.
So much so, that on VERY dynamic vinyl the LP seems to 'slip' on the platter (rather then the belt) in the case of the SME -- if the LP is not fixed with the clamp provided.
This raises the question of 'slippage' of the vinyl on the platter in the case high torque direct OR belt drive, and if no platter clamp is used or even available.

Lastly, if the drive is THAT tightly coupled, then the motor controller's performance comes a LOT more to the fore. With the hole drive line becoming so much more unforgiving with next to no measurable 'slip' it is now unable 'paint over' some dynamic ‘problem passages'.
Fix one thing, and it will reveal the next issue for sure.

‘Too much’ platter weight (never mind just the main bearing implications) in such a 'tight coupled' scenario may just 'over-load' the motor/controller, running behind torque demand and its reverse, producing delay and over-shoot if the platter's inertia is out of tune with the motor's torque delivery and the controllers feedback loop speed.
All this can explain why a more 'benign' coupling might sound better or more natural, even if slightly less 'dynamic'.
Greetings,
The flaws in the way most vinyl was mastered will far out weight what 'perfection' that you chase in the TT design. Once you arrive at the 'perfection' design, it will be time to move on to a base that is no less than a $10K electron microscope table. Then on to other parts of the chain. Please, just enjoy the music.
We will always have different opinions about what platter drive is the "best" because we see here -again - different "schools".
I - again - just want to mention the fascinating idea first proposed by japanese audio engineers about using the string on heavy platter and working with a WANTED and precisely tuned "slip".
This works just great with a precise platter of considerable weight and inertia.
The string with minimal grip and minimal tension does indeed minimize any speed alternations, transmitted vibrations and just have to prevent the platter from loosing speed.
The (only...) trade-off is a long time till constant speed is obtained (1-2 minutes).
On the other hand we have the minimal possible influence from transmission, motor etc towards the platter.
Its the basic principle behind the big Micro Seiki, Melco and Epic turntables.
Add to this the concept of putting the bearing free from horizontal force (counter-bearing) and you have a smooth TT principle which just needs a considerable amount of space, weight, precision tooling (these 3 = money....) and care.
But - as in most other audio "fields" - different "schools" will favor different concepts and "models".
In my opinion theory doesn’t really matter because we can debate it forever and never come up with a consensus. All that really matters is what sounds best to the listener.
The "whatever sounds good" opinion is a consumer attitude and there's nothing wrong with that but can never work as and apply to science nor truth seeking. I certainly hope people who do manufacturing has done more research than just "whatever sounds good" and came up with more educated decisions. Therefore I completely support the kind of work Mr. Mark Kelly has done and appreciate the time he spent in experimenting and, even more importantly, sharing his findings in print with us. Thank you Mr. Kelly.

I have experience with all three drive systems and they all can sound good but, right now, I completely reject using a soft rubber belt. If a turntable has to use something that soft to filter vibration and masking speed irregularities then it needs a better motor, period. In the last decade in belt-drive manufacturing, much has been belabored on fancy platter, thick and shiny, and bearing, thick and shiny, but little has been focused on the actual motor. Enough with wimpy toy motors already!
Hiho :-)
y.s.: >> Enough with wimpy toy motors already! <<

I guess you are fully aware that this type of wimpy motor is supposed to do the same thing as a soft (and long?) belt already. 'Mellow out' any kind of speed variation that's occurring. It screws the dynamics but it sure will be 'smooth'.
Greetings,
I cannot speak generally to the question, but Chris Brady did a demo at RMAF, one year, comparing his rim drive to his belt drive on the same table and system. I'm sure everyone in the room could clearly hear the difference as it was not subtle. The rim drive had a blacker background and seemed to bring out more detail...kind of a veil-lifting effect.
All the comments remind me of the endless discussion of speaker drivers and the material science that relates to it. As many have suggested, whatever sounds best to you, is the best. That goes for all the links in the chain. In the meantime, the cat will keep chasing its tail.
Buconero117,
>>>... the cat will keep chasing its tail <<<
And so the cat is having some entertainment, what's wrong with this?
Cheers,
PS: by the way, I just like how SME tts go about it, a belt drive with dynamics! -- that's why I got one :-)
08-02-09: Axelwahl
PS: by the way, I just like how SME tts go about it, a belt drive with dynamics! -- that's why I got one :-)
For a long time the SMEs were the only belt drives I'd heard that don't mute transients and artificially "relax" the musc. Fortunately, now the Ayre/DPS turntable creates the same sensation for significantly less money. I'm not saying it's as "good" as a $30K SME, but if that's the sound you like and can't spring for a SME, look into the Ayre.

08-01-09: Quiddity
Johnny

... The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range.
How long is the initial transient of a piano note, a string pluck, a drum or cymbal hit? I suspect the initial dynamic jump is well under 1 ms. How large, physically on average, is such a transient "bump" in a record groove that is 1400' long for a 20-minute side? If belt drive flex lengthened that transient by 10-20%, it seems to me we would be talking about parts per million from one standpoint, but possibly a quite audible 15% variation from another.
Johnny B

You don't seem to understand the function of a low pass filter. It is not possible for the belt drive flex per se to affect anything by more than a few parts per million for the reasons given.

A change in belt tension will however create belt creep and this effect will be around 1000 times larger. That was my point.

Mark Kelly
Mark Kelly (Quiddity).

How did you come to choose your moniker? I looked it up:

1. The essence, nature, or distinctive peculiarity, of a
thing; that which answers the question, Quid est? or, What
is it? " The degree of nullity and quiddity." --Bacon.
[1913 Webster]

Anything to do with that?

From the Websters dictionary 1905 edition: "A barbarous term used in school philosopy for essence" - gotta love a dictionary with that degree of vitriol.

My intended career was as an academic in philosophy. My chosen field was logic and the structure of consciousness, especially with reference to linguistics and mathematics.

One of my heroes is Willard van Orman Quine, who was a logician at Harvard.
http://en.wikipedia.org/wiki/Willard_Van_Orman_Quine
One of Quine's books is titled "Quiddities". I rather liked the term so when I established my consulting company I called it Quiddity Technical Services.

I don't like monikers but Audiogon insisted that I register as a business and that I take a moniker which referred to my business name, so there you have it.

Mark Kelly
Excellent story, mine is much simpler.

My Mother and Father picked out Albert Porter for me when I was born and it seemed like a good name for Audiogon as well :^).
While we are getting offtrack...

Mine comes in memory of Colonel Sergei Ivanovich Mosin. He had a fascination of mechanical things enough that the rifle bearing his name has survived from 1891 til this day in one form or another. I respect him because he fully appreciated and practiced the principle "form follows function" even before Louis Sullivan wrote about it.

Win
Back on track...

The discussion so far has been about torque, but in my opinion the most critical component of a turntable may be the platter. With all three types, belt driven, idler driven and direct drive, the platter can be the make-or-break piece because it is the final interface to the record, it is key to how inertia works and it is the interface to the rest of the mechanism. That said, I really believe that a turntable should be seen as an entity because, like the audio chain in your system, it is only as good as its weakest link. There is no single part, no matter how seemingly insignificant, that should be overlooked. Designing a decent one is easier said than done for certain.

Win

And to take that theme and refer back to the OPs question, I might ask: how much of the total inertia of the system should the platter represent? What influence does splitting some or most of the inertia away from the platter have on the perceived "drive" of the system?

It seems to me that many of the designs which are known for having lots of what Albert calls "drive" have moderate mass / moderate inertia platters tightly coupled to a high inertia drive system. If I'm not mistaken Win had a similar concept in mind when he desgned his TT.

Mark Kelly
Platter is important but in my experience the motor is the most important and then combination of platter and bearing. After all the motor is the active component here, hence it's called TURN-table for a reason. It has the most demanding job and requires the most sophisticated engineering that involves electrical and mechanical skills. If you get a good motor, you are more than half way there. Of course, if you use a soft rubber belt to conceal the flaws of the motor then the platter is more important. I do agree that a record player should be seen as a whole system not just a collection of parts.
Interesting this inertia talk.

That raises the (old?) question who should control the STEADYNESS of speed - inertia of the platter, or the motor AND IT'S CONTROLLER.

If the motor sux, or the controller sux, you have to look back to the platter's inertia. If you manage to make it THAT heavy (never mind the resulting bearing problems) there must come a point where any conceivable variation in friction-changes of the needle to vinyl interface become SO SMALL as to approach zero.

I have a notion we have to look for some mighty heavy platter to get there. One expert put two Micro-Seiki on top of each other --- and then waits 5 minutes for the darn thing to stabilize the speed.

You see, we are now starting to move big-time out of the practical useful user-application --- which in turn also sux.

So it's back to the more practical idea as was mentioned above platter-weight not much more then ~ 4.5kg, still using a belt for a tiny bit more forgivingness, than a DD which translates its little faults too immediate into the speed stability.
Lastly a motor / controller package with the best available feedback speed / loop to mankind :-)

A thing to note: that bearing friction has to be present at a controlled level to "damp" the controller feed-back loop, preventing feed-back resonance, so to speak.

Now have a look who is doing something like this, and I guess you'd have a 'best of breed' and still user friendly tt.
Greetings,

Axelwahl,

On your first point: That one's easy. I take it as a truth universally acknowledged that if the motor were not running, frictional forces (of whatever source) would cause the system to slow down and in doing so it would lose kinetic energy.

It therefore must be the case that energy is being put into the system for it to remain at constant speed. The only possible source of such energy is the motor, therefore the motor must have the primary role in maintaining constant speed. All that platter inertia does is to reduce the slope of the decelerations (and equally the accelerations).

Your second point falls foul of a fundamental property of feedback loops, that the speed of the feedback loop must take account of the speed of the "forward" portion of the loop. If you interpose a low pass filter such as the belt and platter in the loop then you must slow the loop down to prevent oscillation. If you leave the belt and platter outside the loop then the loop cannot possibly compensate for losses in the belt / platter system such as torque dependent belt creep.

No free lunch.

Mark Kelly


I want to ask opinions on belt approach that Hiho has mentioned a few times. I was also of the opinion that any kind of compliant belt was not going to be the best solution. It seems in my brief experiences with speed controllers of late that with a DC approach the system does benefit from tight coupling, hence mylar can work very well.

The difference in DC controller operation can make or break this theory of mine. I would characterize one controller/drive system as being similar to the approach Dertonarm mentioned, that of counting on a certain amount of slippage. Another controller, (same motor, different controller) just happens to be one of Mark's old DC controllers, seems to improve with increased tension => no, or almost no, belt slippage. This does require a pretty hefty motor pod to help keep things taught. The presentation of this second DC approach is very much like what I hear with rim drives and maybe some lower end DDs. How much like rim drive I can't say as I don't have a good candidate for A/B.

So I thought I was all set with my drive choice. And then a friend brought over an AC motor and a Kelly AC controller. As you might expect, the cogging of the motor is very apparent with the mylar belt, even with less tension. The best setup was achieved with very little tension and a fair amount of slippage. Even more than what was used with the first DC controller. So it would seem that a more compliant belt would be called for with the AC approach. The amazing thing to me was that even with the huge amount of slippage the AC motor/controller was really kicking the DC arse in many ways.

After learning some these new things for myself I am no longer so convinced of what I thought before about belt compliance. Surely we would all love to have the perfect motor. But since that probably isn't going to happen, it seems to me that the controller becomes more important. At the same time, the selection of the motor and controller would seem to dictate what belt candidates should be considered.

Mark, I am still somewhat surprised that the particular platter/bearing does not seem to influence your designs. Or do you just make it look too damn easy? :-)

Dan

For the kit designs I had two overriding criteria: they had to be as cheap as possible whilst still providing acceptable performance and they had to be almost universally applicable (hence your comment about platters / bearings). Unfortunately this means that they are a long way from optimised for any specific application.

For the bespoke designs I gather as much information as possible, to the extent of getting specific numbers for the rotational moments of inertia of the motors used from the motor manufacturers or in the case of one drive having to measure the numbers myself. I then build a model in a Spice program using some translational analogies and spend a lot of hours doing dynamic modelling.

Depending on the sophistication of the drive, the specific platter and bearing numbers can have some influence on dynamic performance but the most important parameters are the motor and its electrical control. When I am happy that I understand what's going on, we go to prototype.

The results? Well, I think you'll be surprised at what can be achieved with standard AC motors and belts even less compliant than your Mylar when the drive mechanics are understood. Similarly if a manufacturer sends me several samples of a high cost three phase motor and says "do your best then bill me" the results can be pretty good.

The downside is that the controllers end up being quite expensive. I don't know if there's a viable model for producing an aftermarket controller using any of these techniques.

Mark Kelly
Axelwahl says, "One expert put two Micro-Seiki on top of each other --- and then waits 5 minutes for the darn thing to stabilize the speed."

I think the flagship Nottingham Deco took such approach, with a massive 64 pound that is as thick as a microwave and driven by an extremely low torque motor that you have to finger spin it to start. Definitely doesn't seem very user friendly to me. I had a Spacedeck in the house at one point, very quiet table but the sonic was so mellow that it put me to sleep.

I use direct-drive turntables. Sometimes I use them to (VHS)tape-drive a "passive platter". So the motor is any one of my dozen direct-drive turntables. I no longer see these DD tables as record players, they are motors with a 12" pulley, "active platter", along with a controller. The combination of two platters takes up a lot of table space for sure. But they sound good. The only time when I can't hear any improvement from this tape-drive approach is when I use a dd table with a coreless motor. The coreless motor DD table sound just as smooth as the tape-drive set up. I have yet to try it with my Technics SP10mk2 table. It will be fun. I don't have any Denon turntables right now but I would like to try them as they are the only company I know who use an AC motor for their DD turntables.
I have to jump in here, perhaps a little late, but I have definitely enjoyed the banter. Especially the literary references; and I thought I was the only one who kept an unabridged Websters first edition at my reach. And what does my wife mean when she walks in the room and says "if you spent a third of the time you spend on this stereo stuff on our rlationship things would be better". This reminds me of a line from a poem I like "If you can keep your head when all about you are losing thiers and blaming it on you"
Back to the topic:
Question #1- Is the torque(twisting force)acheived by the platter dependent solely(sp) on it's driving force, or does it at some point become a product of it's rotating mass?
#2 If the bearing matches the mass of the platter, no matter how great (e.g. the fan blade on a jet engine), are the problems brought up about bearings solved?
#3 I believe the Feikert Twin TT uses a kevlar belt. Not much stretch there. If the belt is for all practical puposes stretchless, does it become a direct drive?

Thank you all for your responses, I appreciate the time you put in this, even if my wife doesn't.

Matt
HI Matt,

I can't help with the technical questions. I will offer this. My wife and I decided to stop "working" on our relationship after the first three years. That's when my first son came along. After that we just "worked" on making it through the day. It will be 34 years this winter. :-)
Mark,

I think you'll be surprised at what can be achieved with standard AC motors and belts even less compliant than your Mylar when the drive mechanics are understood.

If it isn't giving anything away, how is the filtering by the belt done differently with less compliance in the AC approach? Or am I confused by my own assumptions?
"Similarly if a manufacturer sends me several samples of a high cost three phase motor and says "do your best then bill me" the results can be pretty good."

I resemble that remark. Yuk. Yuk. ;)

I do have a habit of sending motors to Mark, and leaving the task open-ended. It can result in sticker shock, but the result can be stellar.

An external rotor three-phase eddy current motor that has has a 90W draw can be very inefficient, but the payback is in extreme smoothness, and also wonderful dynamics. So, I agree with others that a decent motor is key to high performance. In the case of Saskia, my turntable, the platter gains equivalent mass from this approach, too. The external rotor provides this to a point that when used with an idler it is the equal of a belt drive that has a platter that weighs several hundred pounds. The motor counts for a lot, but the platter can be further tuned to enhance inertia even more. Then, there is the spindle, bearing well and associated parts which also play important roles when it comes to ruble control, dynamic braking, evenness of play, etc. Again, if any aspect is neglected, performance suffers in one way or another.

Win
I've been working with a modified form of the old Empire table for some years now. It has a very powerful motor that has a lot of torque, runs at high speed and has a lot of flywheel action. Years ago I ran an electronics service center- while there I service all sorts of tables including the Technics Sl-1100, the SL1200 and the SP-10.

It is my opinion that the drive does not matter as long as it is robust and executed well. Weak drives just don't seem to do it and I have seen very little in the way of servo-controlled belt drives with weak motors that work right.

However, to my ear the platter pad has a far more profound artifact than the drive! Years ago I was lucky enough to obtain a platter pad that was truly neutral- and use it on a variety of 'tables. With it, the SP-10 sounds identical to a stock Empire and any number of older Pioneer belt drives (the platter pad is heavy so 'table needs a robust bearing to support it).

Without maintaining the platter pad's contribution in audition of all these drive systems, a huge variable is introduced that IMO/IME makes it impossible to ascribe a difference properly. The platter pad should reduce resonance in the platter; IOW the resonant signature of the resultant platter cannot be ignored!

Now it might be that someone here has been this careful- has anyone in auditioning all these different tables (Lenco, Technics, Garrard, Micro Seki for example) been able to keep the resonant signature of the various platters constant, as well as the durometer of the platter pad surfaces? If yes- differences might be ascribed to drive. If no- differences are probably not the drive at all, but the platter's resonant signature as the vibrations in the groove are decoded.

What I am saying here is that the needle playing the LP makes a physical sound and vibration that the LP itself reacts to. If the platter does not control that, you have a coloration. IMO/IME, 95% of table differences are this effect.
Good point, Ralph. Also, if you use this un-named but "very heavy" pad (I assume you mean "mat") on an SP10 or the like, it may have a negative effect on the performance of the drive system, since the servo mechanism was designed specifically for the mass of the stock SP10 platter + mat. Whereas the same mat might have a less deleterious effect on the performance of your Empire.
Hi,
all said sound fine, -- BUT there is clearly a difference between colouration and dynamics!

The platter material / mats / pads / and other damping are ALL colouration items (excluding some really heavy lead-loaded mats adding more mass)

The drive-line performance is an issue with dynamics / timing / rhythm etc. I don't think both should be just dumped into on pot so to speak.

Axel
Ralph,

Have you tried "record periphery rings"? It would appear to benefit warped lps, of which I have a number.

Your feedback would help me in considering same. I've already tweaked the mat and use a spindle weight. My table is a Dual 721 with robust DD motor. FWIW, speed has been rock steady (by strobe) with the 4 or so extra pounds added by "steel/polymer/steel sandwich + carbon fiber donut" platter mat and TTweights heavyweight brass spindle weight.
Axel, I regard differences in dynamics as a coloration, just like tonality and soundstage. All are **definitely** aspects of platter pad vinyl resonance control (or lack thereof).
Jb0194, I think they have advantages if your system will allow them, in controlling warp. Since the platter pad controls the LP's resonance signature, the ring won't do much to help- it will merely insure that the coloration is consistent across the entire surface.

Dan

It would be giving something away, but you are on the right track. It's the design of the filter that takes all the time and effort in the Spice model.

Matt:

Q 1 Asked and answered.

Q 2 No.

Q 3 No.

Mark Kelly