30 years on...

What a completely fatuous argument: the LP12's springs are not in motion during replay, and, in any case, the arm is supported on the suspension as well.

 

It's just nonsense isn't it. You assertion is equivalent to saying that all transistor power amps that follow the classic 'Lin' format are equivalent because they differ only in the 'details'. And then you gloss over all the details...

You seem to be saying that the Linn platter is the weight it is because that's the weight Thorens chose (presumably actually for the TD125?) and that this inevitably causes 'dynamic wow'. It doesn't seem unreasonable to ask you to prove it. What's the moment of inertia of the Thorens platter? Of the LP12? Do they use the same construction drive belts? The same motors? I don't know, and it appears neither do you. This is before we get to the 'dynamic wow' issue which is completely separate.

Paul

 

Well, snipers usually lie down...

But you might be grateful for a suitably sprung platform if you were trying to snipe during an earthquake. The analogy as presented is a straw man.

Paul

 

Isn't the platter mass, inertia whatever irrelevant when the vinyl lies on a loose felt mat anyway?


Cheers

Jason

 

O God, here we go..........

Are you seriously suggesting that the stylus drag is sufficient to move the weight of the record & felt mat, relative to the platter?

 

I said 'inertia about the spindle'. Angular momentum is a function of the moment of inertia and the rotation rate, and is what is significant to the stylus drag argument. I think it's the integral over the volume of dm2/dr where m is mass and r is distance from axis of rotation.

The platter mass itself is obviously significant to the suspension system. I think in general for a suspended turntable we'd like a low platter mass and a high moment of inertia. So you distribute your platter mass around the outside of the platter. Like Thorens and Linn...

Paul

 

Ah .... so that's why it's thicker at the outer rim? Got you.

 

Slightly rather than considerably: the Orbe's platter is 3.5kg (I've just weighed mine), the LP12's 3.75kg (according to Linn specs). So, about 7.7 pounds vs. about 8.2 pounds.

And, indeed, Michell.

I agree there's a lot of nonsense written about high-mass platters, stylus drag, yada yada. That's audiophilia for you, people inventing phenomena because they like worrying.

-- Ian

 

It's the half-pound which makes all the difference, Ian!*

This Thorsten bloke really has written the most abstruse pile of nonsense about hi-fi which I have ever read, and that really is saying something.

* despite the Orbe's pathetic showing in the platter-mass stakes, it doesn't wow, either.

 

The Verdier is actually suspended, with the springs being pneumatically damped.

 

Is that why the Verdier sounds so bad?

 

No, just more likely that it would slip rather than the platter slowing, trying to point out that discussion about platters is even more irrelevant when there is a mat inbetween. Just grab an LP while it is spinning ... bet the record stops and the platter keeps going.


Cheers

Jason

 

How likely is it that the record will slip during replay?

a) Extremely unlikely.
b) Vanishingly slim chance.
c) It's never happened yet.

That goes for any turntable without a clamp. And that's not the function of record clamps, BTW.

 

What is the function of record clamps?

 

I know, thats what I am trying to say. So in answer; c!


Cheers

Jason

 

To clamp records

I use my clamp because my platter's very slippery, and I've got into the habit. It doesn't actually sound any different without it, though. On very warped records some heavy duty clamping seems to help a bit, but I've not got many very warped records.

-- Ian

 

Depends on the deck, usually a mixture of warp suppression and creating a better unity of the record and the platter which should mean less vibration of the record relative to the platter, the rocord and platter become as one grasshopper

... or any number of kooky audio bollocks theories.


Cheers

Jason

 

What dainty little platters they both have.

Tony.

 

Mark the platter, mark the mat. Play a piano recording. Has the mat moved?

Paul

 

Hi,

Well, at least I am in good company:

From: http://www.kabusa.com/ttspec.htm

'Speed drift (Due To Dynamic Stylus Drag) Never Specified
When the stylus encounters a highly modulated groove, it must do extra work in the groove, during this time, friction and drag increases on the drive system. Here we have an affect similar to discharging an electrical capacitor. Based on the duration of the loud passage, and the weight of the spinning platter, there is a time constant that determines how quickly the platter slows down. If the platter is insufficiently heavy (<10 Lbs), the speed can slow sufficiently such that, a moment after the loud passage is over, you become subtly aware of the turntable speeding back up. It can take many years of listening to hear this effect, but like all listening skills, once you attain it, it is with you for life.
Only heavy platter belt drives, or sophisticated direct drive systems can overcome the affects of dynamic stylus drag.'

From: http://www.kabusa.com/TTDRIVE.HTM

'FG Servo Belt Drive

Frequency Generator Servos or Tachometers, offer the most sensitive way to control a DC drive system. The Tachometer provides a direct readout of motor speed and thus is able to control the motor most effectively. This drive system offers the best control of both long term speed drift and static stylus drag friction. It cannot however respond fast enough to dynamic groove friction. But if the platter is heavy enough, the flywheel effect will deal effectively with most dynamic groove friction effects.'

From: http://stereophile.com/turntables/376/

(Stereophile quoting SME Material)

'According to the accompanying literature, the PLL (phase-locked loop) speed-control servo "has the effect of multiplying the rotating platter mass by the loop gain, thereby virtually eliminating dynamic wow caused by groove modulation/stylus drag."'

From: http://www.avidhifi.co.uk/design.htm

'Traditionally motors driving turntables have been low powered AC synchronous devices driving high mass platters. More recently DC and multiple motors have been used, trying to achieve speed stability through rotational inertia of the platter. Motor noise transmitted to the "loop" and cogging, all problems to be solved. During playback the platter is subject to varying stylus drag which, despite the flywheel effect puts load on a weak motor, loosing synchronicity, massively increasing vibration.'

From: http://www.smartdev.com/inspiration.html

'A low drag bearing allows the stylus to display variable drag as the belt compliance allows this (some call this dynamic wow), the effect is a reduction in dynamics coupled with a shifting of stereo image. The more enlightened have seen this and are using stiff tape to replace the belt, it seems they understand the problem.'

From: http://www.originlive.com/dc_drive_brochure.pdf

'Speed stability
The motor requires load compensation to maintain the turntable at a constant speed. This is because the drag of the stylus varies between the inner and outer tracks of a record. Many turntables suffer from about 1% speed drift. Not only is there variation from inner to outer tracks - there is also localised variation when the stylus negotiates complex or heavy passages of music.'

From: http://www.iar-80.com/page13.html

'This means, quite simply, that loud music slows down your turntable.' (after a lengthy coverage of the subject)

I guess they all also write abstruse piles of nonsense.

In fact, Newton, whose discoveries (and the law named after him) illustrate the how and why probably also wrote abstruse nonsense.

L8er T