The belt/belts are also positioned as far below the pivot as practically possible. In this way a small tilt of the platter will result in a larger change in belt tension.
Very interesting Niffy, and really counter intuitive: I thought that a lever arm (distance of the pivot point from belt) multiplies the effects of a non-homogeneous tension (frictions from two idler), but your experience says the opposite This also explains why the solution with three belts can work better.
carlo
addendum
The runout (with the noise) is a big problem, not having a big size lathe. After trying to get a sandstone platter waterjet cut and drilled (not straight, now good as lamp holder) I came to a machined sub platter with 3 register screws: with a dial gauge the runout can be registered under the tenth (tolerance of the sleeve x radius)
Vpi style bearing: I tried with two opposing Teflon V-angles, one up and one down, with the belt forcing the spindle against each other. Result: random friction = irregular rotation. Maybe the surface of Teflon was not smooth enough, or maybe too much: who knows.
Very interesting Niffy, and really counter intuitive: I thought that a lever arm (distance of the pivot point from belt) multiplies the effects of a non-homogeneous tension (frictions from two idler), but your experience says the opposite This also explains why the solution with three belts can work better.
carlo
addendum
The runout (with the noise) is a big problem, not having a big size lathe. After trying to get a sandstone platter waterjet cut and drilled (not straight, now good as lamp holder) I came to a machined sub platter with 3 register screws: with a dial gauge the runout can be registered under the tenth (tolerance of the sleeve x radius)
Vpi style bearing: I tried with two opposing Teflon V-angles, one up and one down, with the belt forcing the spindle against each other. Result: random friction = irregular rotation. Maybe the surface of Teflon was not smooth enough, or maybe too much: who knows.
The sleeve seems to be the part of the bearings that causes the biggest problems, has the largest negative impact on sound quality and is the most difficult and expensive to manufacture.
I got the idea for eliminating the sleeve from the days when I owned a pink triangle anniversary deck. This used an inverted bearing and a Teflon washer in very much the same way as Hiten suggested. I found that removing the washer gave a large improvement in sound quality even though the platter wobbled all over the place. The negative effects of this simple sleeve were still greater than a couple of millimetres of runout. Don't get me wrong, the anniversary is still one of the greatest decks ever made.
Niffy, what is the influence of bearing sleeve on sound, and how would you explain the process?
Walter
nocdplz,
I feel your frustration in making your own platter / bearing as it is totally unforgiving for lack of precision tolerances being maintained. Teflon is not a good material ( soft and "tears" ) for the sleeve part of the bearing. Vespel or Torlon (very expensive) are the best sleeve materials, bronze also works well and is traditionally used for this purpose. . The concept of "just spinning a record" seems very simple, until you try to do it yourself in a quiet accurate manner. You can check into possibly obtaining a Rega or similar bearing. There are lots of Rega mods for platters, bearings, tonearms etc. that work very well and are cost effective on the net.
There are also turntable platters / bearings available on ebay. Good luck.
I feel your frustration in making your own platter / bearing as it is totally unforgiving for lack of precision tolerances being maintained. Teflon is not a good material ( soft and "tears" ) for the sleeve part of the bearing. Vespel or Torlon (very expensive) are the best sleeve materials, bronze also works well and is traditionally used for this purpose. . The concept of "just spinning a record" seems very simple, until you try to do it yourself in a quiet accurate manner. You can check into possibly obtaining a Rega or similar bearing. There are lots of Rega mods for platters, bearings, tonearms etc. that work very well and are cost effective on the net.
There are also turntable platters / bearings available on ebay. Good luck.
Hi Walter,
A normal turntable bearing, be it inverted or non-inverted, consists of two parts. The first one is the thrust plate . This tends to consist of a ball or round ended rod pressing against a pad that can be flat, concave or even convex, like a second ball. The thrust plate takes the entire weight off the platter and the load is thus vertical. I'm ignoring magnetic and air bearings as these are not "normal" turntable bearings. For any material combination of ball and pad there will be a maximum pressure that can be applied safely. Any turntable using the same materials and platter mass and having the same contact pressure will have the same contact area and pressure distribution across that contact area. For example my turntable with a platter mass just shy of 4kg and hardened steel ball and concave thrust pad has a contact point 0.25mm across. Any turntable with the same mass, using the same materials and keeping the same maximum contact pressure will have the same 0.25mm contact point regardless of the shape of the thrust plate used. The pressure gradient across the contact point is always the same with an elliptical profile. As the platter rotates the contact point of the ball slides over the thrust pad creating a frictional torque. The point of maximum torque is always 82% of the radius of the contact point from the centre and the average at 60%. (I accidentally quoted the average as 80% in a previous post). My bearing has its 4kg mass acting at a point only 0.075mm from the centre of rotation. The coefficient of friction between thrust pad and ball is 0.19.
The second part of the bearing is the sleeve. Most sleeves are made of a combination of steel and bronze and are lubricated with oil. The sleeve doesn't take any of the load required to support the mass of the platter. It has to be produced with a very small gap between the shaft and sleeve in order to run true. This gap is filled with a laminar film of oil. This results in a large drag. Bearing shafts tend to be at least 8mm in diameter and are often as much as 20mm for high mass platters. The friction due to this drag is acting 4-10mm from the centre of rotation, 50-130 times further than for the contact point.
In a normal non-inverted bearing you can expect 93% of the friction to be due to the sleeve. Once you add the side force of the belt this is likely to be 95%. That means only 5% of the total energy dissipated is dissipated by the thrust pad. Even if the sleeve dissipates a smaller proportion of its energy as noise it can still easily produce a lot more noise than the thrust pad simply because it is dissipating so much more in total. The sliding velocity in the sleeve is going to be 50-130 times greater than in the contact point average. Of course you still have to have the thrust pad and its noise.
Similarly variations in torque due to inevitable limitations in manufacturing accuracy are going to be greater in the sleeve than the thrust plate. A 10% inaccuracy in the thrust pad is smaller than a 1% inaccuracy in the sleeve.
It's a difficult thing to pin down what the actual effects on sound quality are of the different components within the bearing. If you remove one component in order to listen to the other the bearing tends to stop working all together. As I previously mentioned the one exception to this was my pink triangle anniversary. Removing the Teflon sleeve resulted in a sound that can best be described as more open. This is despite the runout going to pot which would have had a detrimental effect on VTA, azimuth and wow. The gains were greater than the losses. Of course you couldn't sell a deck with this level of runout (2mm) even if it sounded as good as the pink. (actually you probably can, have you seen the magnetically levitated deck. It must have at least 5mm of runout. But that is sold as a gimmick)
Niffy
A normal turntable bearing, be it inverted or non-inverted, consists of two parts. The first one is the thrust plate . This tends to consist of a ball or round ended rod pressing against a pad that can be flat, concave or even convex, like a second ball. The thrust plate takes the entire weight off the platter and the load is thus vertical. I'm ignoring magnetic and air bearings as these are not "normal" turntable bearings. For any material combination of ball and pad there will be a maximum pressure that can be applied safely. Any turntable using the same materials and platter mass and having the same contact pressure will have the same contact area and pressure distribution across that contact area. For example my turntable with a platter mass just shy of 4kg and hardened steel ball and concave thrust pad has a contact point 0.25mm across. Any turntable with the same mass, using the same materials and keeping the same maximum contact pressure will have the same 0.25mm contact point regardless of the shape of the thrust plate used. The pressure gradient across the contact point is always the same with an elliptical profile. As the platter rotates the contact point of the ball slides over the thrust pad creating a frictional torque. The point of maximum torque is always 82% of the radius of the contact point from the centre and the average at 60%. (I accidentally quoted the average as 80% in a previous post). My bearing has its 4kg mass acting at a point only 0.075mm from the centre of rotation. The coefficient of friction between thrust pad and ball is 0.19.
The second part of the bearing is the sleeve. Most sleeves are made of a combination of steel and bronze and are lubricated with oil. The sleeve doesn't take any of the load required to support the mass of the platter. It has to be produced with a very small gap between the shaft and sleeve in order to run true. This gap is filled with a laminar film of oil. This results in a large drag. Bearing shafts tend to be at least 8mm in diameter and are often as much as 20mm for high mass platters. The friction due to this drag is acting 4-10mm from the centre of rotation, 50-130 times further than for the contact point.
In a normal non-inverted bearing you can expect 93% of the friction to be due to the sleeve. Once you add the side force of the belt this is likely to be 95%. That means only 5% of the total energy dissipated is dissipated by the thrust pad. Even if the sleeve dissipates a smaller proportion of its energy as noise it can still easily produce a lot more noise than the thrust pad simply because it is dissipating so much more in total. The sliding velocity in the sleeve is going to be 50-130 times greater than in the contact point average. Of course you still have to have the thrust pad and its noise.
Similarly variations in torque due to inevitable limitations in manufacturing accuracy are going to be greater in the sleeve than the thrust plate. A 10% inaccuracy in the thrust pad is smaller than a 1% inaccuracy in the sleeve.
It's a difficult thing to pin down what the actual effects on sound quality are of the different components within the bearing. If you remove one component in order to listen to the other the bearing tends to stop working all together. As I previously mentioned the one exception to this was my pink triangle anniversary. Removing the Teflon sleeve resulted in a sound that can best be described as more open. This is despite the runout going to pot which would have had a detrimental effect on VTA, azimuth and wow. The gains were greater than the losses. Of course you couldn't sell a deck with this level of runout (2mm) even if it sounded as good as the pink. (actually you probably can, have you seen the magnetically levitated deck. It must have at least 5mm of runout. But that is sold as a gimmick)
Niffy
Hi Hottattoo, my frustrations depend only from my fundamentalist concept of DIY: from scrap, on my own (tools, skill, ideas). That's the challenge for me, not to assemble Frankenstein TTs, or make me do parts by others.
Add to this that I do not like to fool myself, and that the experience made me quite demanding, and you will understand why to abandon the idea of a diy turntable: simply because with a 9x20 Chinese lathe it is almost impossible (vibrations) to get the tolerances - finish necessary for a truly silent bearing.
There are no good or bad materials, imho, only the right materials to be used for the task: for bearings as for platters, plynths and so on. And for different solutions conceived for very different TT concepts.
Hi Walter: the influence of the bearing on the sound has been reported in detail by Niffy's experience+ knowledge. (a lot to learn for me too)
I always thought there were too many variables to be able to understand something, but instead I could say several things about the noise produced by different types of couplings, because I lost some time hearing my different trials with a stethoscope.
Since I like rigid TTs and a rigid disk to platter coupling, I know that the noises of the bearing are the first to reach the cartridge, and it is certainly not an heavy mass that can cut them: you can hear the clang of a train coming, through miles of rails and tons of iron.
carlo
Add to this that I do not like to fool myself, and that the experience made me quite demanding, and you will understand why to abandon the idea of a diy turntable: simply because with a 9x20 Chinese lathe it is almost impossible (vibrations) to get the tolerances - finish necessary for a truly silent bearing.
There are no good or bad materials, imho, only the right materials to be used for the task: for bearings as for platters, plynths and so on. And for different solutions conceived for very different TT concepts.
Hi Walter: the influence of the bearing on the sound has been reported in detail by Niffy's experience+ knowledge. (a lot to learn for me too)
I always thought there were too many variables to be able to understand something, but instead I could say several things about the noise produced by different types of couplings, because I lost some time hearing my different trials with a stethoscope.
Since I like rigid TTs and a rigid disk to platter coupling, I know that the noises of the bearing are the first to reach the cartridge, and it is certainly not an heavy mass that can cut them: you can hear the clang of a train coming, through miles of rails and tons of iron.
carlo
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Niffy, your research, as I've said before, may challenge the whole R@D institution. Understanding the problems in order to eliminate or minimize their effect, IMO is a right way to go. It is not a dominating approach in the hi-end industry, and so, there is a room for DIY-ers activity.
As to my turntables, I'm satisfied with traditional bearings, because their noise and vibrations are of negligibly low level. That's why I've never thought about the elimination of bushing before. Possibly, it is worth trying in my case too.
Carlo, if we could eliminate the motor vibrations and flatter... Some people are back to spring motors of 1920-x years of the last century, and I even thought of trying them myself.
As to my turntables, I'm satisfied with traditional bearings, because their noise and vibrations are of negligibly low level. That's why I've never thought about the elimination of bushing before. Possibly, it is worth trying in my case too.
Carlo, if we could eliminate the motor vibrations and flatter... Some people are back to spring motors of 1920-x years of the last century, and I even thought of trying them myself.
Hi all,
A couple of additional points to my last post.
The use of a sleeve type bearing with its thin film of oil will introduce some degree of damping, probably quite a lot. Whether this is beneficial or not is going to be open to debate. In many instances I have found that the addition of damping to be detrimental, the suspension of the deck for instance. The removal of damping may account for some improvements in sound quality.
With the bearing in my deck the only contact between the platter and the sub-chassis is a single very small point. This may offer better mechanical grounding.
I have not performed any experiments that would allow me to confirm whether these hypotheses are plausible or not.
One thing is certain. It would be impossible to build a traditional style of bearing with the equipment that I own. I'm with Carlo when it comes to wanting to build everything myself. Not being able to make a traditional bearing forced me to design an alternative. In doing so I could address what I thought was the main drawback of traditional bearings. I think my sleeveless design is in many ways superior to what is used in commercial decks.
Niffy
A couple of additional points to my last post.
The use of a sleeve type bearing with its thin film of oil will introduce some degree of damping, probably quite a lot. Whether this is beneficial or not is going to be open to debate. In many instances I have found that the addition of damping to be detrimental, the suspension of the deck for instance. The removal of damping may account for some improvements in sound quality.
With the bearing in my deck the only contact between the platter and the sub-chassis is a single very small point. This may offer better mechanical grounding.
I have not performed any experiments that would allow me to confirm whether these hypotheses are plausible or not.
One thing is certain. It would be impossible to build a traditional style of bearing with the equipment that I own. I'm with Carlo when it comes to wanting to build everything myself. Not being able to make a traditional bearing forced me to design an alternative. In doing so I could address what I thought was the main drawback of traditional bearings. I think my sleeveless design is in many ways superior to what is used in commercial decks.
Niffy
Hi all,
The last paragraph in the previous post isn't quite right. It make it sound like I designed the sleeveless bearing because I couldn't build a sleeved one. I decided on the sleeveless approach because of the result of my experiment on my pink triangle deck and all the subsequent research. That the design I came up with is much more DIY friendly was a bonus.
Niffy
The last paragraph in the previous post isn't quite right. It make it sound like I designed the sleeveless bearing because I couldn't build a sleeved one. I decided on the sleeveless approach because of the result of my experiment on my pink triangle deck and all the subsequent research. That the design I came up with is much more DIY friendly was a bonus.
Niffy
Hi all,
Ok got my first Igus stuff in, now going for a Proxxon cut off saw
Dumped the floating platter for now, to much risk in flow overs when manipulating records, rings and the like
One of my tech sparring partners, mr Grimm, has a lot of words about eccentricity- with reason.
So looked at Nakamichi’s TT, the tx 1000 centers on 2 axes,
Some nice shots under the hood:
YouTube
the dragon ct, uses 1 pusher to center the platter
YouTube
My question: what system is better and what is enough?- one axis should be enough-even though the measurement and 1axis alignment is a 45 degrees, when object is rotational, it should not matter, right?
Best
Coolerooney
Ok got my first Igus stuff in, now going for a Proxxon cut off saw
Dumped the floating platter for now, to much risk in flow overs when manipulating records, rings and the like
One of my tech sparring partners, mr Grimm, has a lot of words about eccentricity- with reason.
So looked at Nakamichi’s TT, the tx 1000 centers on 2 axes,
Some nice shots under the hood:
YouTube
the dragon ct, uses 1 pusher to center the platter
YouTube
My question: what system is better and what is enough?- one axis should be enough-even though the measurement and 1axis alignment is a 45 degrees, when object is rotational, it should not matter, right?
Best
Coolerooney
Hi Coolerooney,
New bits of material to play with is always exciting. I'm not sure about the idea of a floating platter, I think a platter needs a solid connection to ground. If you want to float the platter the best thing to float it on will be a couple of microns of compressed air.
One axis of adjustment is all that is required so long as the eccentricity lines up with that one axis.
Those nakamichi decks are works of engineering overkill. They look excessively complicated. Do you know how accurately they centre the record? Centering to an accuracy much better than 50um is unnecessary as that level of accuracy is less than the groove pitch. Moving the entire top of the platter is counterproductive, you only need to move the spindle.
Niffy
New bits of material to play with is always exciting. I'm not sure about the idea of a floating platter, I think a platter needs a solid connection to ground. If you want to float the platter the best thing to float it on will be a couple of microns of compressed air.
One axis of adjustment is all that is required so long as the eccentricity lines up with that one axis.
Those nakamichi decks are works of engineering overkill. They look excessively complicated. Do you know how accurately they centre the record? Centering to an accuracy much better than 50um is unnecessary as that level of accuracy is less than the groove pitch. Moving the entire top of the platter is counterproductive, you only need to move the spindle.
Niffy
Hi,
iIrc only the TX1000 had a ´mechanism to adjust the top platter against the sub platter.
The smaller Nakamichi had the top platter just laying loosely on top and it was pushed by a little lever into the right position.
I find the latter alot more elegant. Naka almost showed a diy attitude here .-)
jauu
Calvin
iIrc only the TX1000 had a ´mechanism to adjust the top platter against the sub platter.
The smaller Nakamichi had the top platter just laying loosely on top and it was pushed by a little lever into the right position.
I find the latter alot more elegant. Naka almost showed a diy attitude here .-)
jauu
Calvin
....sleeve bearings frustrations ...
Thanks Cooleroney for posting those videos; not for the old Nakamichi (a moving top-platter centers the disk while off-centering the platter balance) but because at the youtube runout tag I found these:
YouTube
YouTube
YouTube
Well. now I feel less frustrated: if they sell those stuff ....
This is far better, YouTube
Rega knows well where to spare his money (e.g. for mdf), and where not
More or less with my registrable platter I came at this 4 - 5 hundredth runout, pulleys no one at all (if you can't make a true-running pulley on your lathe better starting a new hobby...)
carlo
more on youtube platter wobble tag
Thanks Cooleroney for posting those videos; not for the old Nakamichi (a moving top-platter centers the disk while off-centering the platter balance) but because at the youtube runout tag I found these:
YouTube
YouTube
YouTube
Well. now I feel less frustrated: if they sell those stuff ....
This is far better, YouTube
Rega knows well where to spare his money (e.g. for mdf), and where not
More or less with my registrable platter I came at this 4 - 5 hundredth runout, pulleys no one at all (if you can't make a true-running pulley on your lathe better starting a new hobby...)
carlo
more on youtube platter wobble tag
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Hi Carlo,
The three YouTube videos showing platter wobble (runout) are quite reassuring to me following my tweek to reduce it on my own deck. Before I changed the idlers and belts and with a really off balance record my runout was a lot less than in either of the first two videos. After the change my runout is pretty much undetectable. Having listened to a lot of vinyl since the change I think that there is a definite improvement in sound quality. It's not a huge change just a subtle improvement. I think the best word to describe the change in sound is immediate. This is probably due to a slight improvement in the speed stability due to a reduction in warp wow. I've got a couple of different belt materials on order to see if I can wring any more improvements out.
Niffy
The three YouTube videos showing platter wobble (runout) are quite reassuring to me following my tweek to reduce it on my own deck. Before I changed the idlers and belts and with a really off balance record my runout was a lot less than in either of the first two videos. After the change my runout is pretty much undetectable. Having listened to a lot of vinyl since the change I think that there is a definite improvement in sound quality. It's not a huge change just a subtle improvement. I think the best word to describe the change in sound is immediate. This is probably due to a slight improvement in the speed stability due to a reduction in warp wow. I've got a couple of different belt materials on order to see if I can wring any more improvements out.
Niffy
Niffy, as you know the first obsession of any machinist (even a sunday machinist) is to have everything perfectly aligned (someone loses years in his lathe shimming). So for me a perfectly leveled (rigid) turntable + platter is just the starting point: this means bearing squared to the plinth, spindle squared to the platter; all running true, with the lowest tolerances possible.
The problem of the sleeve is friction+noise, not the damping: if the bearing rotates in hydrostatic regime (= minimum tolerances+great finish) the rotation generates relevant pressures on an oil film of a few microns: so very rigid (liquids are incompressible).
After the change my runout is pretty much undetectable.
on your system a dial gauge (even a finger type) ca't be used: perhaps the old method of the cat whisker used for bicycle wheels?
Your solution is very interesting, especially using the gyroscopic effect of a platter with the weight all peripheral, but for me the problem of the belt remains: if elastic it is difficult to prevent the wobble, both for the traction of the motor (a small subplatter does not help, imho, more direct traction) both for aging. Using rigid belts (mylar, spectra ect) would solve the problem, but it would be difficult to maintain the contact: an elastic register for the pulleys axis?.
carlo
The problem of the sleeve is friction+noise, not the damping: if the bearing rotates in hydrostatic regime (= minimum tolerances+great finish) the rotation generates relevant pressures on an oil film of a few microns: so very rigid (liquids are incompressible).
After the change my runout is pretty much undetectable.
on your system a dial gauge (even a finger type) ca't be used: perhaps the old method of the cat whisker used for bicycle wheels?
Your solution is very interesting, especially using the gyroscopic effect of a platter with the weight all peripheral, but for me the problem of the belt remains: if elastic it is difficult to prevent the wobble, both for the traction of the motor (a small subplatter does not help, imho, more direct traction) both for aging. Using rigid belts (mylar, spectra ect) would solve the problem, but it would be difficult to maintain the contact: an elastic register for the pulleys axis?.
carlo
how about a video Laserdisc placed shiny side up and pointing laser pointer on its surface and noticing its reflection movement on wall or something ?
Regards.
Hi Carlo,
The aim is to get the platter running true and level with minimal noise and preferably a solid connection to ground. In many ways it doesn't matter how this is achieved as long as it is. Even with my previous single belt setup I was attaining results that were better than achieved by most decks. But I knew it could be improved so the three belt system was born. It has a level of runout on a par with the best. You are quite correct in saying that I can't use a dial gauge as shown in the video to measure runout. I did position a probe (a wooden cocktail stick) just above the edge of a record as it was played. Using a wide angle camera lens as a magnifying glass I looked at the gap between the record and the probe as the record revolved. I tried this on a couple of records and couldn't discern any changes in the gap. I would reckon that the variation at the edge of the platter is less than 50um even on a badly off balance record. This would put the runout in the same sort of league as the deck in the last video. So even though the belt is elastic it does adequately prevent the platter from wobbling. Some new belt materials have just arrived this morning. The current belt is made of round nitrile rubber (Dr Feickert style) 1.5mm in diameter. I have now got some 2mm diameter nitrile rubber that should have 56% the compliance, 180% the stiffness. This can't really improve the runout as it's about as good as it can be but it might help in other ways. I also have some 2mm silicone rubber (Clearaudio style) to play with. This appears to be much more compliant than the nitrile rubber. I can't go above 2mm as the gap between the idler mount and platter is small.
You also mentioned the traction of the belt. By removing the sleeve from the bearing the friction has been massively reduced. A lot less force is required at the periphery of the sub-platter to maintain rotation. A belt driving a low friction bearing is much less likely to slip so I'm less likely to suffer belt slippage than if I was using a sleeved bearing and running on the periphery of the platter.
I do have to use a belt with a some compliance as my motor and idlers are not adjustable in position. I calculated that 0.7N of tension should be more than adequate to prevent any slippage. To set this tension I have to test the stretchyness of the belt then make each belt to take this into account. The motor has a smaller pulley than the idler so needs a slightly longer belt, 1-2mm depending on belt material.
The gyroscopic effect of the platter at the speed of rotation of a record is very small and plays a very minor role.
There are three main effects of platter runout. The first is variation in azimuth, this will effect all arm designs equally and is consistent across the record. The other two are VTA error and warp wow. These will be most pronounced at the beginning of a record. They will also effect shorter arms more than long ones. As I have a very short arm, 55mm, keeping runout low is very important to me
Niffy
The aim is to get the platter running true and level with minimal noise and preferably a solid connection to ground. In many ways it doesn't matter how this is achieved as long as it is. Even with my previous single belt setup I was attaining results that were better than achieved by most decks. But I knew it could be improved so the three belt system was born. It has a level of runout on a par with the best. You are quite correct in saying that I can't use a dial gauge as shown in the video to measure runout. I did position a probe (a wooden cocktail stick) just above the edge of a record as it was played. Using a wide angle camera lens as a magnifying glass I looked at the gap between the record and the probe as the record revolved. I tried this on a couple of records and couldn't discern any changes in the gap. I would reckon that the variation at the edge of the platter is less than 50um even on a badly off balance record. This would put the runout in the same sort of league as the deck in the last video. So even though the belt is elastic it does adequately prevent the platter from wobbling. Some new belt materials have just arrived this morning. The current belt is made of round nitrile rubber (Dr Feickert style) 1.5mm in diameter. I have now got some 2mm diameter nitrile rubber that should have 56% the compliance, 180% the stiffness. This can't really improve the runout as it's about as good as it can be but it might help in other ways. I also have some 2mm silicone rubber (Clearaudio style) to play with. This appears to be much more compliant than the nitrile rubber. I can't go above 2mm as the gap between the idler mount and platter is small.
You also mentioned the traction of the belt. By removing the sleeve from the bearing the friction has been massively reduced. A lot less force is required at the periphery of the sub-platter to maintain rotation. A belt driving a low friction bearing is much less likely to slip so I'm less likely to suffer belt slippage than if I was using a sleeved bearing and running on the periphery of the platter.
I do have to use a belt with a some compliance as my motor and idlers are not adjustable in position. I calculated that 0.7N of tension should be more than adequate to prevent any slippage. To set this tension I have to test the stretchyness of the belt then make each belt to take this into account. The motor has a smaller pulley than the idler so needs a slightly longer belt, 1-2mm depending on belt material.
The gyroscopic effect of the platter at the speed of rotation of a record is very small and plays a very minor role.
There are three main effects of platter runout. The first is variation in azimuth, this will effect all arm designs equally and is consistent across the record. The other two are VTA error and warp wow. These will be most pronounced at the beginning of a record. They will also effect shorter arms more than long ones. As I have a very short arm, 55mm, keeping runout low is very important to me
Niffy
Hi Niffy, please note I dumped the floater...
When I see the Kuzma accessoires list for the air tangent arm, I sorry, but that’s OTT, high pressure compressor, airfilter, water separator, hoses, to place in another room.....- agreed an air bearing platter may require less extremes— I applaud the search for the max, but we must also realize that most of us (apologies young ones) are pushing the years, which also means the hearing is degrading- the 4000Hz dip is upon us (or has already arrived) hahahah
The Nak Dragon brochure quotes 20 microns run out, after centering, so not bad at all.
The TX1000 has a readout showing the eccentricity
On what to move, I think that can be debated, sure there are pros/cons for both approaches- I would go for the platter, allows for the main bearing and spindle to remain in place
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Hi, Niffy & nocdplz
It is nice talking about keeping machining tolerances as tight as possible and it is pretty amazing how good us amatures have accomplished this goal. I check my machines every few months for accuracy and when a high precision job is at hand.
I was at a Rocky mountain audio show a few years ago when the Kronos turntable was all the rage, using 2 platters with one platter spinning the opposite direction. This system easily cost 250k+ and "professionally " set up but while sitting in the sweet spot about 12' away I could see that the top platter was visually wobbling about .020" or so. I spent about 1 hr. listening to vinyl that I knew well and could not hear any real difference in sound quality, and I deliberately tried. When I was done, I approached the person giving the demo and told him about the wobble in in the top platter and he said that I was the only person to mention this but everything sounded wonderful so he didn't think it mattered much !!! That room got glowing reviews from several audiophile magazine reviewers. Go figure. This video was from Munich. just to show the turntable.
YouTube
It is nice talking about keeping machining tolerances as tight as possible and it is pretty amazing how good us amatures have accomplished this goal. I check my machines every few months for accuracy and when a high precision job is at hand.
I was at a Rocky mountain audio show a few years ago when the Kronos turntable was all the rage, using 2 platters with one platter spinning the opposite direction. This system easily cost 250k+ and "professionally " set up but while sitting in the sweet spot about 12' away I could see that the top platter was visually wobbling about .020" or so. I spent about 1 hr. listening to vinyl that I knew well and could not hear any real difference in sound quality, and I deliberately tried. When I was done, I approached the person giving the demo and told him about the wobble in in the top platter and he said that I was the only person to mention this but everything sounded wonderful so he didn't think it mattered much !!! That room got glowing reviews from several audiophile magazine reviewers. Go figure. This video was from Munich. just to show the turntable.
YouTube