Direct drive vs belt vs rim vs idler arm

Richard/Lew,
I have added no mass to either the Victor or the Raven turntables.
In fact....I am playing the TT-101 WITHOUT the standard rubber mat. A 1mm thick sheet of pigskin being the only separation between vinyl and aluminium platter.
With the Raven...I am playing the records sitting directly on the copper platter top-plate.

Ketchup,

it might be possible to improve its speed stability by using a higher viscosity oil.

Have you seen my video of the TT-101 with the three tonearms going up and down monitored with the Timeline?
I have seen no visual evidence of any other turntable equalling this degree of accuracy and speed stability?
Did you note the 3150 Hz frequency on the Feickert sine-wave test with 2 tonearms on the platter?
How much improvement do you visualise?

Halcro

The reason for my question was that it is popular to add significant inertia via metal aftermarket mats. The thought is that this can screw with the servo, which if excessive, it should. I was curious, given the tight control, spot on frequency, if any significant change to the platters inertia had been made.
Great result.

Richard and Henry, Well actually Henry has made a change to platter inertia, in the downward direction, by removing the platter mat. I am guessing, based on my DP80, that the Victor OEM platter mat is a rubber one. If it's like the DP80 platter mat, it weighs a bit more than half a pound. The pigskin mat probably weighs far less. Now that Henry has this measurement system up and running, it would be very informative indeed if he/you could repeat your experiment with the OEM rubber mat in place, so see what happens to those notches. Then also you could do experiments with some of those very heavy aftermarket mats, e.g., the ones made by TT Weights if you have one lying around, to see just how much and at what point extra weight affects the servo. (Or just stack a bunch of LPs on the platter.) We've been talking about the possible effects of hi-mass platter mats here for years, with no actual data.

This is all about speed stability, servos, and the like. I have no doubt that the TT101 probably sounds better with the pigskin mat than it does with its OEM mat. Same holds for the DP80, on which I use a Boston Audio mat.

01-24-13: Richardkrebs
Halcro
The reason for my question was that it is popular to add significant inertia via metal aftermarket mats. The thought is that this can screw with the servo, which if excessive, it should.

Krebs Upgrade

Hi RichardKrebs
As part of coming up with the Krebs upgrade were you able to determine what the weight threshold is for an SP10MKII platter before it starts to ^%*% with the servo. Very much interested in your opinion as I have a couple mats. Thanks.

Ct0517
The Krebs upgrade causes no material change to the platters inertia and I have not done any tests on the effect, if any, of extra mass via heavy matts or clamps. This was part of my line of questions to Halcro on any changes to the 101's platter's inertia.

So the quick answer is that I don't know where the threshold is, but would very much like to find out.

Just a little plug here. Customers of both MK2 and MK3 upgrades have universally noted a marked improvement in percieved speed stability. Some of these customers are using heavy aftermarket metal mats and clamps/weights, which appear to have no negative effect on the servo.
Ken McCarty's review of the MK3 upgrade on Albert Porter's system thread covers the speed topic nicely.