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Monaco Gp, actual vs average speed.

i_should_coco said:
So how does the motor drive the platter? Magic?
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I assume Keith is attempting to imply that unlike a belt, or an idler there's no direct source of physical contact between the motor (pre-se) and the platter. Of course you can say the same about any DD deck they are all effectively 'none contact'- if you ignore the fact that one half is bolted to the chassis and the other half bolted to the platter.

So if you choose to look at it with those eyes then seeing as one half of the motor is actually rigidly connected to the platter then you could claim it is more directly connected than a belt drive where the motor can be completely decoupled from the rest of the deck, whereas with a DD the main bearing shaft almost always links he two halves of the motor together via the chassis and the platter.
 
sq225917 said:
I assume Keith is attempting to imply that unlike a belt, or an idler there's no direct source of physical contact between the motor (pre-se) and the platter. Of course you can say the same about any DD deck they are all effectively 'none contact'- if you ignore the fact that one half is bolted to the chassis and the other half bolted to the platter.

So if you choose to look at it with those eyes then seeing as one half of the motor is actually rigidly connected to the platter then you could claim it is more directly connected than a belt drive where the motor can be completely decoupled from the rest of the deck, whereas with a DD the main bearing shaft almost always links he two halves of the motor together via the chassis and the platter.
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Well indeed, one half of the motor kind of has to be attached to the platter by definition. It's not a case of 'looking at it with those eyes', IMO, to claim that the half of the motor which is bolted to the platter is not part of the motor is at best extraordinarily disingenuous. In fact, assuming the motor is quiet enough, having it more closely coupled is a big advantage over a belt or idler as any compliance here would makes accurate speed control far more difficult.

Of course, I don't know the details of the drive system, for all I know they could have introduced some sort of magnetic coupling between the motor and platter, but that would be daft because then you have the same problem as a belt drive, i.e. Trying to control the platter at the end of a spring. That's why I think it's FUD.
 
I have no doubt its a normal DD motor setup, two separate parts linked by the main bearing and each rigidly fixed to either chassis or platter.
 
Here's what the marketing release that Keith is quoting from has to say.

• Direct drive with no mechanical contact in the horizontal plane. The lowest noise drive and bearing design architecture possible.

• No Mechanical Contact platter bearing. It is a passive oil immersion hydrodynamic non-mechanical contact bearing. It has absolutely no mechanical contact in the horizontal plane thus, providing the most
noise free bearing possible.

• A vertical thrust bearing that is separate and isolated from the spindle bearing and drive system. This ensures rock solid platter control under all conditions. It uses a high tolerance high sphericity silicon nitride ceramic ball riding on a hybrid alloy bearing pad.

• An enormously rigid plinth made of carbon fiber composite coupled with Grand Prix Audio exclusive internal damping. It is truly a 21st Century plinth, high rigidity combined with extraordinary damping in a single structure.
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What I will say is that playing with a carbon sandwich material at a manufacturer some years ago showed it's bloody good at damping resonances.
 
• No Mechanical Contact platter bearing. It is a passive oil immersion hydrodynamic non-mechanical contact bearing. It has absolutely no mechanical contact in the horizontal plane thus, providing the most
noise free bearing possible.

• A vertical thrust bearing that is separate and isolated from the spindle bearing and drive system. This ensures rock solid platter control under all conditions. It uses a high tolerance high sphericity silicon nitride ceramic ball riding on a hybrid alloy bearing pad.
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These two statements by Monaco seem rather contradictory to me. So the bearing shaft is bathed in oil and has a spiral machined in to it so it carries oil across the surface - that's not very unique as such and frankly, I'm not convinced such a spiral is even needed.

Although there may be no horizontal contact in the bearing, it is rather a mute point and there is vertical contact and that is where most noise is generated in such bearings.

It's true that magnetic bearings introduce a vertical compliance, but this is inherently well damped and little exists to excite it (assuming half a motor isn't attached to it ;)) - the benefit is that you can achieve a genuinely contact free bearing - horizontally and vertically - zero wear and ultra low noise.
 
Good question !

My post #42 on page 3 five days ago asked the questions. Click here to see it : http://www.pinkfishmedia.net/forum/showpost.php?p=2171231&postcount=42

Post #51 four days ago, said they would ask the designer

It was all really about their statement "roughly 20 times more speed accurate than the best of the belt drives and about 10 times more
speed accurate than the best of the direct drives and probably more like 20 times for most of them also."

But instead of answering the questions, they asked me questions. Questions about SME, which is odd since they must have measured one using their test method, the same test method that their claims are made on, to have said what they said ?

Normally when a manufacturer makes bold claims and they are questioned, they would 'make hey' by accurately and succinctly answering everyone in full.

I get the impression they are not pleased that their statements should be questioned, very odd ?

Regards

Dave
 
What you need Dave is an optical encoder with 4800 markings per revolution. But judging by the way their speed measurements seem to cycle up and down every 60 or so samples I would say that their 'printing' of the optical disc is just as likely to be innacurate in much the same way as a test tone. I haven't seen the optical encoder ring but this single fact leads me to believe that they use a flat disc on the underside of the platter as opposed to a vertically aligned ring of encoder marks on a vertical outside surface. The point being you can't print an accurate strobe disc with such thin markings as the angular error as a ratio of the line width becomes too high as you increase the number of segments, similarly the trigger width for the reader reduces as you go thinner. It looks and smells like enhanced resolution but its actually greater ' 'uncertainty'.

Dave you could try printing a disc with 4800 segments, just for a laugh. 12 lines per degree on a 30cm diameter its pretty damn thin. Building a counter to measure this should be a trivial task though, 2400hz is small beans.

Of course if his markings do run around an outer edge then I take this comment back. But as I said I'm confident they don't and that any measure based on a flat disc will suffer from x, y/ radial positioning accuracy error.

I'm happy to wait for Keith's deck to arrive. An FM demod using Serge's din approved test record will show all anyone needs to see. If it beats Serge's EMT, the best result on that thread so far, then the designer will be vindicated.
 
It's true that magnetic bearings introduce a vertical compliance, but this is inherently well damped and little exists to excite it (assuming half a motor isn't attached to it ;)) - the benefit is that you can achieve a genuinely contact free bearing - horizontally and vertically - zero wear and ultra low noise.
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A couple of questions. Why is it inherently well damped? In its crudest form it must behave like a spring. Is it the drag caused by the lubrication in the bearing? With regard to exciting it, can't it excite itself by fluctuations in the field between the opposing poles as the platter rotates? Id have thought external vibration had the potential to excite it as well. One other thing, isn't such an arrangement always trying to displace itself horizontally and only doesn't because it is constrained?

(I'm not doubting the efficacy of your implementation having heard the needledrops, just asking general questions about maglev bearings).

When I worked for a speaker company I had a pencil stuck to my desk with blu tac & 2 small opposed ring magnets placed over it so that the upper one floated above the lower. Couldn't happen without the pencil!
 
pure sound said:
A couple of questions. Why is it inherently well damped?
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Because the mass of the platter effectively pre-loads the magnetic field - though not in some designs.

pure sound said:
Is it the drag caused by the lubrication in the bearing?
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Partly.

pure sound said:
With regard to exciting it, can't it excite itself by fluctuations in the field between the opposing poles as the platter rotates?
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In theory - if the speed of rotation was just right - but I have seen no evidence that the very low speeds in a turntable generate any such artefact.

pure sound said:
Id have thought external vibration had the potential to excite it as well.
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Yes, external vibration is more likely - that's why a proper level of isolation is required - but any deck should include such IMO.

pure sound said:
One other thing, isn't such an arrangement always trying to displace itself horizontally and only doesn't because it is constrained?
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It depends how you configure the two opposing elements. It's possible to build it in such a way that a narrower field rides on a wider one and the central shaft effectively stops one from toppling off the other - at the point of balance there is no sideways force. However, accurate alignment of the components is essential.
_________

My comments only related to my own use of such a bearing - they aren't intended to endorse other implementations. In particular, I would say that Clearaudio do a number of things wrong.
 
Thanks Mark. I asked because I was talking to Martina of L'art du Son 501 fame last weekend, noted she was using a maglev bearing in the new motor they fit to that deck & asked why they didn't maglev the main bearing as well. Her reply was along the lines of "we're injecting a lot of energy into this system from the motor, we need to have it grounded somewhere".
 
Dave Cawley said:
Good question !

My post #42 on page 3 five days ago asked the questions. Click here to see it : http://www.pinkfishmedia.net/forum/showpost.php?p=2171231&postcount=42
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Your questions are not answerable.

I suggest you read the GPA 'white paper' and rephrase them.

But I read the document and GPA claim a peak speed variation of less than 0.002% and describe how they arrived at that claim. A quite browse at the VinylEngine shows that the Technics SL1200 is spec'd by its manufacturer at a W&F of 0.025%, average and weighted. So that's an order of magnitude worse. Thorens claim 0.06% for the TD160, that's more than 20x worse. So on the face of it Keith's marketing claim has a basis (pun intended).

Paul
 
That sounds like a 'motor isolation fail' acknowledgement.

There's a simple test for this Guy, just compare two silent groove drops with and without maglev. We did this with Marks implementation and it was worth -3db pretty much across the board with a slightly greater reduction than this level at the rotation frequency. That's not to be sniffed at.

What motor arrangement does she have on the deck?
 
You mean you don't want to answer them !

And please don't patronise me by measuring your own timetable one way, and then quote others a different way.

I think we have all had enough of this.

Poor show

Dave
 
Paul R said:
Your questions are not answerable.

I suggest you read the GPA 'white paper' and rephrase them.

But I read the document and GPA claim a peak speed variation of less than 0.002% and describe how they arrived at that claim. A quite browse at the VinylEngine shows that the Technics SL1200 is spec'd by its manufacturer at a W&F of 0.025%, average and weighted. So that's an order of magnitude worse. Thorens claim 0.06% for the TD160, that's more than 20x worse. So on the face of it Keith's marketing claim has a basis (pun intended).

Paul
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Do you really think it's comparing apples with apples Paul?
 
To be fair to Keith, it isn't his marketing claim - he is just reporting the claims made by GPA.

Also, Paul R doesn't work for GPA so I don't see how he can be accused of failing to answer quetions directed at them.
 
pure sound said:
Thanks Mark. I asked because I was talking to Martina of L'art du Son 501 fame last weekend, noted she was using a maglev bearing in the new motor they fit to that deck & asked why they didn't maglev the main bearing as well. Her reply was along the lines of "we're injecting a lot of energy into this system from the motor, we need to have it grounded somewhere".
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Hmm.. her response doesn't add up to me Guy. When she says the energy has to be grounded, why is that and why should the main bearing be the appropriate place? If she means vibration, then the motor needs refinement, not a bandage.
 
sq225917 said:
That sounds like a 'motor isolation fail' acknowledgement.

There's a simple test for this Guy, just compare two silent groove drops with and without maglev. We did this with Marks implementation and it was worth -3db pretty much across the board with a slightly greater reduction than this level at the rotation frequency. That's not to be sniffed at.

What motor arrangement does she have on the deck?
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I do have a slight issue with how rumble & self noise can really be measured accurately. I suppose a comparison as you suggest can show a difference in a specific application such as Mark's deck.

Markus would be better placed to comment on the translation of this review but I gather the latest implementation of the 501 is considerably quieter than the earlier version as is reported in 'Audio' here.

http://www.garrard501.com/aud1005_p0120_Garrard501.pdf

There are pictures showing how their latest motor is mounted which seems not dissimilar to the original arrangement.

I believe they used two differing means of measuring rumble, one of which, using the Thorens device, theoretically takes the test record's quality out of the equation. I'm a little dubious about it but apparently there are people who can set it up to give useful measurements.

As idler decks go it did seem uncommonly quiet.
 
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