Tables That Feature Bearing Friction

Dertonarm, the heavy platter, slip coupling approach focuses on only the issue of motor cogging. This approach does not deal with the issue of stylus drag, or any other variability in drag. Contrary to popular beliefs platter mass changes how stylus drag affects speed but does not correct it. A massive platter will reduce the magnitude of the variation but extends it over a longer period of time. A light platter will conversely allow a larger speed variation but it enables more rapid recovery. Heavy vs. light platters exhibit different sounding degradations but they are still degradations.

Intimate coupling of the motor to the platter is the only way to effectively deal with stylus drag. But intimate coupling also makes problems from cogging worse. So in the end a compromise between the two is needed. A DC motor needs less isolation than an AC motor so the compromises will and should be different. Personal preferences also will dictate the ideal compromise. For example idlers with AC motors have poor isolation from cogging, but more intimate coupling. The result is excellent rhythm and timing but finesse and low level detail are sacrificed. Some like the idler compromise and others don't.

If you start with a very low cogging motor then a better compromise can be achieved.

Dertonearm, I don't know whether you have already done so, but you might like to go over to Vinyl Asylum and search on the musings of Mark Kelly, a very smart fellow, on the various platter drive mechanisms and their pros and cons. Of additional interest is his work to develop drive systems for AC motors that reduce motor noise and cogging.

Dear Teres,
stylus drag is only an issue if the record is not firmly clamped down to the platter.
If the record is not firmly clamped down, we do not need to talk about correct application or technical issues anyway. This is basic parameter. If securely clamped down it becomes part of the moving system and its mass - hence: heavy platter with high inertia.
As I said before - this is only one approach and certainly not the only one in igh-end audio, but it is the approach of physic and technical engineering.

A heavy platter will have no variation once it is on speed.
Any possible loss in speed is avoided before it occurs - by correct allpied coupling with string (= very low grip but enough to avoid loss of constant speed). Thus the error does not occur but the only task for motor and string is to hold the speed - nothinh else.
Stylus drag do only have an effort when the record itself "slips" on the platter surface (and believe me - I do use a cartridge which really can "drag". But of course it is only going on a record which is firmly - really firmly - pressed down on the platter).
Sometimes it really helps illustrating forces in motion with vector diagrams on a sheet of papaer. Visulising what really is going on does set some points clear really fast.
This is physics - thus it can fairly easy be determined when you allow the facts to spread.
Trying to correct any variation in speed as fast as possible ............
The result is constant back and forth in speed.
In other words - you implement unstability by doing so.
Every technical engineer into dynamics or constant torque will tell you that this is futile.
Turntable is pure physics - not taste, not opinion.
Too often in High-end audio people get the impression that physics laws have been invented during the development of audio components.
Not so.
Extremely few audio components - mechanical ones like tonearms, cartridges and turntables - do really take correct applied physics into account.
Otherwise we would have much more better components around.

Dertonarm, we are talking about physics. The issue of stylus drag has been hotly debated before. It is a fact that any drag, regardless of how small will slow a platters rotation. A large platter mass spreads the variation over a longer period of time, but does not and cannot eliminate it. It's basic physics. Any amount of energy added or removed to the system will directly affect speed.

Now what can be debated is the audibility of such a small effect. Logically it seems quite implausible that a force as tiny as stylus drag could be audible. The audibility of the things being discussed here certainly are in the realm of opinion and theory.

Regardless of the theory there is a great deal of evidence that techniques that target stylus drag (like bearing friction and intimate coupling) produce positive, audible results. This would suggest that the theory of audible stylus drag is correct, but it certainly falls short of proof.

Thankfully, turntable design is not pure physics. A good design also includes compromises, tastes, experimentation and even some guesswork. Otherwise turntables would all look and sound the same. Really boring...

Dear Teres, yes, I could grant your last post with some technical counterpoints and facts, but the only result will be argument.

But I can not resist.

****Thankfully, turntable design is not pure physics. A good design also includes compromises, tastes, experimentation and even some guesswork. Otherwise turntables would all look and sound the same. Really boring...*****

Well - turntable design is pure physics.
A turntable is a rotating machine.
That rtation has to be constant and its dynamic forces have to be that large that the extraction of the modulation by the tonearm/cartridge system have no side-effect on the constant rotation.
Furthermore the whole machine has to be suspended from building resonance.
Period.
Would you argue about a wheel and its function??

Stylus drag is a very small sliding force in constant motion and is - coupled with any serious platter (of course not if the LP lays just on the platter and is not firmly clamped down) - really neglectable. Its a force smaller by several magnitudes compared to the energy the stylus puts into the platter while modulating the groove information. A force smaller by several magnitudes compared to any motor generated vibration.

It is not a magic stone nor does it inhibit mystery unknown physical energy which puts it outside the Einstein Continuum ( however - many audiophile seem to believe just this and are supported by commercial audio advertising....).
The fact that "taste, compromises, experimentation and even some guesswork" is included in the design of turntables is the reason why almost all turntables do indeed "sound" different and most do sound pretty boring.
If the NASA had handled the Apollo - Mission that way, man would have never set his foot on the moon.

I have yet to see a turntable design done right.
I have yet to see a turntable with written standard specifications to start with.
So far we have a few good amateurs, but no professional anywhere.