Alternative platters ?

[Gordon Steadman]

A query for you scientist types. My brother in law is/was a design engineer. designed machines for Metal Box. He took one look at my TT and said the platter should be much heavier to take advantage of the flywheel effect. My TT is based on a Sansui DD motor and the platter is extremely light but well damped.

I would have thought that the control systems would find it easier to regulate the speed if the platter was light. If there is a lot of mass, wouldn't the variations have a longer period as the corrections would take longer to be applied? This would then sound like a slow wow and be a disaster on piano music and the like.

Certainly, mine is rock steady and piano music sounds solid and decays naturally with no hint of any 'warblin' (Richard)

[FunkArt]

Indeed, Martin...

Arthur, I hear what you're saying, but surely mass acts as the catalyst for the knock-on effect on inertia? Therefore, the existence of too much mass is the root cause of the problem.

Therefore, in the case of aftermarket platters for the Technics, any new design should not have any more mass (be heavier) than the stock platter, as otherwise one encounters the problems being described here in relation to 'hunting', and consequently audible 'warbling' on playback.

Marco.

Seriously, no Marco.
As Richard put it, a heavy (very heavy?) record clamp (of which, quite a few exist in the market) would now satisfy your condition of "mass acting as a catalyst"...only you'd get no noticeable, for want of an effect, warbling / hunting effects.
Now, as we seem happy with bake-offs, we'll use our trusty rolling bin and flatten said massive clamp into a disc. Et voila, at some point we will end up with hunting = warbling.
Slightly simplistic but I hope you get the idea.

Arthur

[MartinT]

It's momentum (strictly, angular momentum) that needs to be kept in the range of the Technics platter, not mass.

[Oldpinkman]

A query for you scientist types. My brother in law is/was a design engineer. designed machines for Metal Box. He took one look at my TT and said the platter should be much heavier to take advantage of the flywheel effect. My TT is based on a Sansui DD motor and the platter is extremely light but well damped.

I would have thought that the control systems would find it easier to regulate the speed if the platter was light. If there is a lot of mass, wouldn't the variations have a longer period as the corrections would take longer to be applied? This would then sound like a slow wow and be a disaster on piano music and the like.

Certainly, mine is rock steady and piano music sounds solid and decays naturally with no hint of any 'warblin' (Richard)

I'm not the scientist - but the interpreter. Broadly you are right. Inertia (the flywheel effect) can help with stability in some systems (the original LP12) , but not a DC motor which needs servos to maintain its speed. As Arthur has been (trying) to point out it isn't mass as an absolute (either for servo hunting, or the flywheel effect) but where that mass is distributed to (inertia). What you want mate is a nice Pink Triangle. I know a man with spares in his loft

[FunkArt]

It's momentum (strictly, angular momentum) that needs to be kept in the range of the Technics platter, not mass.

By Jove I think he's go tit

[Reffc]

That seems right Martin. Increased angular momentum won't cause hunting or wow. It means in terms of the control and motor that relative changes of speed will just be slightly slower but that the increased inertia means that once up to speed, there should be less call for deviations from the right speed due to reactions caused by stylus drag forces. Belt drive decks have used this principle for years. My only observation is that the power supply matters. If it's not regulated then variations in incoming supply will cause speed fluctuation changes. If I wanted to pimp my Technics, the areas I'd concentrate on would first and foremost be the power supply.

[MartinT]

go tit

Are you talking about my private life?

[Gordon Steadman]

What you want mate is a nice Pink Triangle. I know a man with spares in his loft

Wot.......does 'spare' mean what I think it means?

Always willing to try stuff in the interests of disinterested interest.

[MartinT]

Increased angular momentum won't cause hunting or wow

Actually, Paul, we're saying just the opposite. Increased angular momentum certainly affects the Technics circuit, causing speed to be constantly over-corrected, which causes that 'warble' effect (now the official reference for the unstable speed heard when a 1210 doesn't like the platter it's been given).

[Oldpinkman]

Wot.......does 'spare' mean what I think it means?

Always willing to try stuff in the interests of disinterested interest.

"DC motors" in my previous reply, should have been DC motors operating at low rotational speed (direct drive) - but you knew that!. Actually it's Owen who has the spares, but offered them to me for tests and evaluations we were discussing. Not sure how to get one over to you and know its' set up right, but can investigate. What arm would you plan to plonk on it (or do you want to borrow one of those too??) Sue is warming to the idea of a wee trip to the Charente, so i can pack a PT for you to play with. But you don't like belt drive suspendeds...

See if we can sort something out once the dreaded 31 Jan deadline is out the way. Might bring out a Pip too!