The Wonderful World of Turntable Design AKA: Dave's Fugly World Of TT Wank

HiFi
21

a serious question: has anyone heard the 47 labs deck with two platters, two belts and a kind of an idler in between?

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Not herd it but to illustrate…

koma-main.jpg800×435 241 KB

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Junji Kimura says about the design:

The conventional wisdom to control turntable’s vibration/resonance is to damp and/or isolate the resonance by the use of suspensions, damping materials, heavy mass loading, etc. While those techniques are effective in certain ways, it is impossible to fully control the resonance, and it often comes with serious side effects. I’m taking an opposite route. Let the resonance and vibrations run freely between the component and the environment but simplify its route and the mode. That is why the plinth is directly coupled to the main feet. Ideally, it should stand only on this one foot like a rotating tap (‘Koma’ in Japanese), thus eliminating the twisting force created between the rotating platter and feet placed outside of the dead center of the spindle.
For this method to be most effective, the component should be rigidly coupled to the environment. We recommend a hard/solid platform and a shelf with rigid structure to set Koma on.
As for the effect of the counter rotating platter, imagine a single platter turntable placed on a boat floating on calm water. No matter how we smooth out the friction of the rotation, we can not completely eliminate it, and given enough time, the force created by the rotation would be transmitted to the turntable base, to the boat, then to the water, making the boat rotate with the rotation of the platter and cause ripples on the water surface. The counter rotating platter is to neutralize this force created by the primary platter.

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brilliant!

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A good view of it here though the vid is in Japanese:

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He’d have been better off isolating the motor vibation fom the platter imo. Counter rotating platters lick dead dogs dirty dicks.

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Ah, the voice of experience :+1:

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I can confirm that when I set my tt up in a boat, the boat did not revolve, thus confirming Junji Kinura’s statement above.

This, of course proves that counter rotating platter turntables shit on all other designs :grin:

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Except Techie 1210’s, of course. :innocent:

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30

Only on an boat though, and only if the black and decker workmate has been tuned correctly to offset the unnecessary food of the wonky bit.

:grin:

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31

:flushed: wrong thread - you want diet & fitness

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I have, it doesn’t have two belts though, one belt drives both platters and only runs along half the circumference of the platters the motor is mounted on the left with a vertical pulley and there is a passive pulley on the right hand side. Was in a complete 47 Labs set up with Cain Card and humpty’s or numpty’s what ever they are called. It certainly looked very nice, don’t think I’d abandon my PT’s for one though, and would much prefer Jims Kronos.

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http://www.sakurasystems.com/reference/koma.html

Wow not cheap.

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It doesn’t confirm his statement, only the physical effects that he ‘predicts’ on the basis of his statement. He’s right that a single rotating platter would tend to cause the boat that it’s on to rotate in the opposite direction, and that two counter-rotating platters wouldn’t. But his explanation that friction is involved in this is horse-poo. If you think about it for a moment you’ll realise that friction tends to drag the object which is supposed to be stationary in the same direction as the moving object, not the opposite direction. The reason the boat turns the other way under a single platter is the much more fundamental principle of conservation of angular momentum. As we spin the platter up from stationary we give it some angular momentum. Since, between them, the platter and the boat had no net ang mom to start with, they must still have no net ang mom once the platter’s spinning. So the boat must acquire equal and opposite ang mom to that of the platter, which it does. If there are two platters then their ang moms match and the boat doesn’t have to spin.

But why does anyone care ? From a music point of view, why would the (very, very slow) rotation of the boat matter ? Even more importantly when the turntable’s coupled not to a boat but to the whole planet earth why would the absolutely infinitesimal change in the earth’s rotation needed to balance the platter’s rotation matter ? If you were worried about this you’d have to be massively more worried about the effects on the earth of other big bits of rotating kit (power station generators, fairground rides etc). The JET project has two flywheel generators which spin up to 225rpm with each rotor weighing 775 tonnes https://www.euro-fusion.org/fusion/jet-tech/jets-flywheels/ ! I don’t think they’re counter-rotating.

VB

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Yes, JET is all very well for fusion research but would you want to listen to Norah Jones on it?

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Why would you want to listen to Norah Jones full stop? :poop:

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37

I didn’t really set my tt up on a boat anyway - I was lying about that bit :laughing:

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Don’t beat yourself up about that. Albert Einstein did practically no experiments at all in the real world - he did them all in his head Thought experiment - Wikipedia.

VB

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I think Jim’s thought experiments mostly include meat and his belly.

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40

No, no. He’ll have been up to this, I’m sure:

“A thought experiment is a device with which one performs an intentional, structured process of intellectual deliberation in order to speculate, within a specifiable problem domain, about potential consequents (or antecedents) for a designated antecedent (or consequent)”

VB