How much does rock-solid speed stability cost?

Francisco, I have no problem meeting you. I just have a situation here at home that does not lend itself to having guests at this time. I hope you understand that. It has nothing to do with you or Lak. I couldn't have any guests in here right now.

I think you need to look at something with a non-cogging DC motor system. And also with a "non-hunting" speed controller.

As you have noticed, the ear is much more sensitve to flutter variations, than to the much slower wow variations. AC synchronous motors have a cogging effect that causes this flutter, and it can be noticeable. A properly made DC motor can be non-cogging and relieve this problem. However, these can suffer from problems too, depending upon how the speed regulation is accomplished. But generally, they have variations primarily in the wow area. And they can be made to have very low wow variations. This combination of low variations, combined with the confining of the variations into a less-sensitive type of variation(wow) , can lead to better sounding speed stability.

No motor system is perfect on a turntable. There are drag forces which tend to slow the platter in regular and irregular ways. When the motor system attempts to correct for these slowdowns, it must speed things up slightly. It is the method employed for driving the platter, AND the speed control system that affect things. Rapid corrections lead to flutter, slow corrections lead to wow. Cogging motors lead to flutter, no matter what the speed control consists of.

Heavy platters can also do some good in keeping speed regular, by inertia. Normally these are found in the higher priced turntables, although there are some heavy platter models in your price range.

3 turntables in your price range, that I am aware of, use non-cogging DC motor systems. They are Teres, Michell, and Origin Live.

The Teres Model 135 is unsuspended and string-driven, which leads to less speed interaction between the platter and belt. It also has a pretty heavy 15 pound platter. It has a closed-loop optical feedback system that constantly monitors platter speed via a optical strobe sensor on the platter, and keeps the controller aware of the actual real-time speed conditions of the platter and not just the motor. The controller is programmed to respond very quickly, but apply speed change very slowly. This eliminates the "speed hunting" which can lead to flutter from the controller. Alot of design went into the Teres motor system, and since it is a modular design, it can be purchased separately, and applied to other turntables with good effect. I am aware of improvements in speed control being made to VPI, Basis, Verdier, and others, by replacing the motor and control systems with Teres units.

The Origin Live Aurora turntables use a lighter platter and a suspension. They rely more on the motor for speed control than platter inertia. Speed is regulated and monitored at the motor, and not the platter itself. However, their DC motor and control system is fairly highly regarded, and is available separately also. It has been applied to Rega, and Linn Sondek turntables with good success to improve their speed control and sound quality. They have a couple of DC motor and controller kits on their website. Also their turntables can be seen there.

The Michell Gyrodec has only recently changed to a DC motor system. It apparently also uses a speed controller that senses speed at the motor, not the platter. Reports are that this system is an improvement over the previous AC motor system they used. Their platter is lighter than the Teres, but heavier than the Origin Live.

Oh, and there are a couple of other less-known units out there that use DC motor systems to good effect, such as Redpoint, Progressive Engineering, Bogdan, Pink Triangle. Most of these are not in your price range, except Pink Triangle Tarantella.

In the higher end tables, there can be some mitigating design criteria which will allow AC motors to sound more acceptable. However, I am still of the opinion that a well-designed DC motor is inherently better for this application.

Now, before this direct-drive love-fest gets too out of control, let's talk about some other issues.

First, the "belt-drive crowd" does get it, and there are turntables out there that do not succumb to any of the things that Moncrieff points out in his turntable article.

For example, a quality ironless-core, non-cogging DC motor provides a perfectly smooth output. So using a motor of that type takes you a good part of the way there. Next, using a non-suspended turntable takes the subchassis interaction out of the equation. Third, having a non-stretch belt, combined with the above 2 things, eliminates the "stretch-release-stretch-release" syndrome that Moncrieff talks about. So no cog, no platter/belt interaction, no RC-tank effect interaction with belt and subchassis. What's left? Motor speed control. And heavy platters provide the momentum needed to reduce/eliminate the effects of stylus drag, making speed adjustment very infrequent, and maybe not even needed during the play of the LP. If speed adjustment is required, slow application of this adjustment will make it nearly or totally unnoticeable. A quartz-lock mechanism will not allow slow applications of change, and make immediate changes in a very small variation tolerance, so speed does not vary alot in amplitude, but it does vary alot in frequency. It "hunts" for speed. Up and down and up and down. This is true in either belt-drive or direct drive. Some may say it is perfect because of tight specs, some may disagree. So, as you can see, there are belt systems which do not suffer from these "demons" that Moncrieff waxes so epically about.

Now, direct-drive motors are inherently directly connected to the platter by their shafts, and all motors vibrate. ALL. When the motor vibrates, this vibration is directly coupled to the platter, and the platter vibrates. The vibration of the platter during play can and will cause information loss or distortion, since the record is moving microscopically under the stylus in directions other than the time axis. Better main bearings can minimize this effect. So can heavy, well damped platters.

Belt-drives on the other hand, have the motor somewhat isolated from the platter by the belt, and much of the motor vibrations are damped by the belt, and gone by the time they reach the platter. Since they invariably have some reasonably heavy platter weight, any vibrations coming into the platter will be of low magnitude, and easy for the platter to damp.

As I tried to show here, a well thought out belt drive table has much to recommend it, including good speed control and high vibration isolation, and there are a number of belt drive turntables that perform at extremely high levels. Poor belt drive tables are not an accurate representation of what belt-drive can do, just as poor direct drive tables aren't a good representation of what direct drive can do.

The absolute worst combination possible, is a cheap direct drive, cogging motor, quartz-locked, light platter turntable. These were typical in the late 70s mass-market units. They vibrate, cog, and hunt, with very little compensation from platter weight. Next up is a a cheap belt drive with a poorly designed subchassis, rubber belt, AC cogging motor, and cheap light platter. Neither of these is a very good choice. These are primarily what Moncrieff was talking about. IMO.

At the highest levels, both technologies may be good, but the execution of each design will determine how great it is.

Speed control is very important, but it does not exist in a vacuum. Vibration induced into the platter is also an important aspect of the design. They should not be considered as separate from each other, since the overall performance of the turntable is dependent upon BOTH of these parameters, and not just one or the other. This is why bearing design, platter design, motor and speed control, and vibration control and damping, are included in turntable design. Failure at any one of these criteria will result in a poor sounding turntable. The steps up the scale of performance reflect the proper addressing of all these points together.

Yes, Francisco, I realize the magnets are built-in to the platter. That makes the platter part of the motor, and the spindle is the motor shaft, and the main bearing is the motor bearing. That is the point that I was making.

I'm simply pointing out design methodology. Certainly you agree that nothing is perfect.

I know Lak is interested in a turntable. He's emailed me several times. I don't know what he will end up buying. His price range favors the 1200. You don't really have to A/B against a Teres, just against any sub-$3k tables like a Basis or VPI or something like that. If it can beat any of those, then it is well worth the savings to get the 1200. If it can't beat those, there's no sense in even comparing to the Teres.

The answer to your last question is, "torque".