Direct Drive

A direct drive transmits motion to a system or object requiring actuation without the use of any further mechanical components.

@mijostyn - the energy dissipated by the vibration of a very low mass arm onto the stylus (like a Rega) is less than the vibrations coming up from the motor through a platter, no matter how heavy. It is 2 different philosophies.

I would be interested in measuring the actual vibrations at the record while it is spinning if possible, both with and without the stylus on the record, which takes into account the platter mat (or isolator in my case). Probably pretty hard to do, so the best you can do is listen and Rega's come out very highly regarded.

As an example to the light platter/plinth and minimum force/energy motor extreme , take a look at Rega's Naiad. That is what the P8 and P10m are based on. It is absolute minimalist. Expensive at about $40K, but that's the philosophy. Of course, it should be isolated on a wall shelf or a platform like a Townshend (or both). To me, it is the ultimate quiet table. Roy Gandy states correctly that a turntable is simply a vibration measuring machine and he strives to create the lowest internally generated noise possible.

OP,

Wow. Sorry to hear. I grew up in a suburb of Chicago.

I still remember driving down and trying out my first car… used. Bought it, ran… until the battery ran down. That is when I learned what the pulley in the truck was for… but could not be reinstalled. Several huge investments in major engine repair later… well, finally gave up and my parents helped me buy a new car… $1,999.

A doberman? Not a good sign.

Hopefully, this is not a story like that.

@dover and @testpilot are not wrong.

DD motors are controlled by computer speed measurement and are constantly being speeded up and slowed down to achieve the designer's aim of a perfectly stable speed.  In the event they cannot achieve a stable speed because they are never running at the same speed, aka cogging.   @billwojo the evidence is in the engineering specifications of DD turntables that state they have constant speed monitoring and adjustment.  Written in black and white.

As Dover says, this is analogous to digital control of digital sources where clock error is responsible for perceived speed instability known as jitter.

The alternative approach of using high platter mass and Newton's first law to maintain speed consistency through inertia is a far better approach.

@clearthinker 

I think that we need to step back and look at drive alternatives a little more accurately. A well tuned PID controller will not constantly speed up and slow down, provided the motor controller architecture is well designed.. The phenomenon you mention does exist in poorly implemented systems and is called hunting. Cogging is a characteristic of some motors due to their physical build. (Slotless, coreless motors, properly made are zero cogging and have vanishingly low torque ripple.) 

Synchronous motors, widely touted in these parts for belt drive and rim drive, under a varying load, say playing a record, do hunt about their average if you measure them with sufficient granularity. Synchronous motors therefore exhibit the very characteristic you rail against in a DD system.

The answer to smooth speed is only partly helped by high inertia. What matters more is the frequency response of the drive. A function of the platters inertia and the motor's torque. Then there are a multitude of other factors to take into account when designing a drive system, no matter what type of architecture you choose.  Please view the youtube link here. Note how quickly the arm, which obviously has mass, is pulled across the tank and in so doing how it lifts the weight in the glass bottle. At times the arm is held for some time against the edge of the tank. Inertia won't save you under these conditions. The platter will slow down and a belt, thread, tape or rim drive, would slingshot the paltter up to momentary over speed once the high stylus drag reduces. A properly implemented DD will also do this, but at a much lower magnitude.

I realize that I'm opening Pandora's box here and I'm not looking for a debate on the subject. We all have our favorites  But please look at the video and then consider what would be the best drive architecture to counter this dynamic load. It is an insanely difficult task to control a platters speed under dynamic conditions. All drives have their pros and cons. I happen to believe that modern DD is superior at this. of course others disagree and that's just fine with me.

Скатывающая сила как измерить - YouTube