Stylus-Drag..Fact or Fiction?

Mike, Yes you have to ask for it and it will probably cost you an additional fee. Gabon ebony has a specific gravity close to 1. 1 is the specific gravity of water. So Gabon ebony is very stiff and heavier than most wood. Once it is dry it is also very stable. Great arm for Koetsu's and Air Tights. Problem with it is that it is rare and very difficult to dry. Usually you wind up wasting 30 to 40% of the wood in the process. Good Gabon Ebony is jet black. Black piano keys use to be made out of it. I use it for details in cabinets like drawer pulls, handles, inlay and such. It turns very nicely. 

Usefull information here.

https://www.rarewoodsusa.com/product/ebony-gabon/

"Phoenix, Thank you for that explanation. Do DC motors cog at all?"

Any motor with iron pole pieces will exhibit cogging.  In a DC motor, the magnets are stationary but the rotor coils are wound on steel laminates with poles which also produces cogging.

Some of the better BLDC motors have stators with skewed poles (angled slots rather than vertical) so the rotor sees more or less a constant magnetic reluctance and produce much less cogging.

But an AC synchronous motor could still exhibit cogging, if it is poorly designed with an inadequate number of poles.

But one should look at the rpm of such motors- instead of running at 33 rpm like a direct drive, 1800 rpm is common; at that speed cogging simply isn't a thing.  It becomes a thing when the frequency of the event is slow enough that it falls within the perceptual (time) range of the human ear.

By comparison the speed variation caused by a stylus totally dominates the field.

Most of the direct drive motors (at least the better ones) are coreless so they have no cogging. An 1800 RPM motor is a 4 pole induction motor; the stator does not have the poles and gaps that an AC synch motor will have. When you turn an induction motor by hand there is no cogging because there is no permanent magnet in the rotor. The rotor is magnetized by the rotating field, but that requires a certain amount of "slip" to operate and is a function of the torque load. Because of this slip, induction motors are not truly synchronous which introduces another variable in speed control.  Induction motors are speed sensitive to voltage as well as torque, where AC synch motors are unaffected by either.  DC motor speed is affected by voltage, temp and torque load.  As stated previously by others, there’s no free lunch and there are strengths and weaknesses to each design choice.


Stylus drag is fairly constant so in most cases, it is inaudible. While there is a measurable change in speed caused by stylus drag that varies from the start of a record to the finish, it is rather small and extremely slow changing and mostly inaudible. Changes in speed with groove modulation exist in theory, but I have never seen any data that claims to measure or quantify it; it must be extremely small. Heavy platters with lots of inertia will have a positive effect on this phenomenon, because changes in groove modulation are short duration (by definition) and more inertia will reduce short term speed variations.

In my experience, the biggest change in speed of BD tables is caused by the warming of the belt and bearing oil viscosity; it is not uncommon to see speed drift of 0.2~0.3 RPM over a 45 minute playing time which is audible to those with pitch sensitive hearing and if corrected all at once, audible to just about everyone.