Your example of a heavy platter that keeps rotating for 1 min, once the motor is disengaged, will give you change of angular velocity dω/dt at any moment in those 60 seconds.
Regardless of whether you have a really heavy platter and large friction forces, or a modest moment inertia platter and low friction.
Without a control mechanism, any fluctuation of motor torque will result in a disturbance of platter rotational speed.
( it likely takes 2min to calculate 1/2m1(r1)2 + 1/2m2[(r2)2 + (r3)2] + 1/2m3[(r4)2 +(r5)2] , and 2 hours minus 2 minutes to write it down
)
Empirically the platter mass that Garrard Linn and Thorens use is about right . Some have the theory that the platter is like an anvil. They see the stylus as needing the mass below. Very hard to say except those that are lighter or heavier don't seem ideal. As the Garrard has far more torque it isn't about the lower wattage motors refusing to rotate the high mass. A Garrard with a high mass platter just doesn't sound right. Viedier said magnetic levitation required when high mass. Most bearings regardless of design seem happiest with a moderate mass. Possibly it is a simple calculation of typical bearing loading which I would guess to be mostly the same for many turntables. What you really don't want is high friction and deformation at the bearing point. My turntable was like a Garrard 301, none of these choices needed to be made as Garrard had done all of the work for me . All I did was use the best materials and as Linn hope better sounds better. Hope is much of what it is. Not everything works. I saw that a LP12 was a TD 150. So I took a 301 and threw money at it. I couldn't easily fail as I changed absolutely nothing. Like a tuned engine the bolt on bits were logical improvements. I guess Linn taught me what to do. We have the world record for idler drive at - 79 dB weighted. Transrotor beats it at - 90dB ( belt ) . I think a Denon also.
The point about the mass , balance, bearings is that these are things that are so easy to get right. There is no excuse to get it wrong. Linn did the very best whilst being conventional. The Linn bearing point is multi lapped to a mirror finish. The outer section of the point of the LP12 bearing is a rough finish. It is still like a mirror when rough . Linn told me that the rough bit is to encourage turbulence and it costs less to do. Lets be clear Linn's rough bit is other peoples precision engineered bearing. The Linn tip is so polished as to almost look like melted lead solder before it sets. Very unusual, I have seen many bearings and none like Linn.
What seems the next very easy step is to have some bearing drag. This is set by clearance and viscosity. SAE 30 is not too bad. ATF transmission oil should be OK. Motorcar oils not ( additives ) . Verdier thought drag very useful. The Garrard eddy current brake has a similar effect as drag except the graphs look different. No mater as it is the effect at a given speed that counts.
How the motor and usually belt works is 100 % what is near impossible to get right. Good luck.
The point about the mass , balance, bearings is that these are things that are so easy to get right. There is no excuse to get it wrong. Linn did the very best whilst being conventional. The Linn bearing point is multi lapped to a mirror finish. The outer section of the point of the LP12 bearing is a rough finish. It is still like a mirror when rough . Linn told me that the rough bit is to encourage turbulence and it costs less to do. Lets be clear Linn's rough bit is other peoples precision engineered bearing. The Linn tip is so polished as to almost look like melted lead solder before it sets. Very unusual, I have seen many bearings and none like Linn.
What seems the next very easy step is to have some bearing drag. This is set by clearance and viscosity. SAE 30 is not too bad. ATF transmission oil should be OK. Motorcar oils not ( additives ) . Verdier thought drag very useful. The Garrard eddy current brake has a similar effect as drag except the graphs look different. No mater as it is the effect at a given speed that counts.
How the motor and usually belt works is 100 % what is near impossible to get right. Good luck.
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It takes 30 sec to unscrew a not corroded bolt. It takes time to unset a rusted bolt from it’s rusted nut plate...
The platter of my TD-160 takes 100-105 sec to stop when cold started. This increases gradually to 120-125 sec after ½ hour of operation, remaining constant thereafter.
With an ambient temp of 22d C., the temperature inside the bearing well increased only 1.3d C suggesting that oil viscosity didn’t change during operation but oil wetting of the bearing sides changed.
I had oiled the bearing assy two years ago. SAE 30 (the cheapest Mobil motorcar mineral oil).
Hiten, the diagram you linked to plus the USA and UK links in the article show a long term freq variation of +/- 0.1Hz max. and a short term 1/10th of it. I wouldn’t worry about it. If I was very cautious, I would only place a low pass noise filter in front of the synchronous motor.
The biggest rotational velocity stability offenders in a belt driven platter is the elasticity and slippage of the belt as Nigel says.
There are DD TTs which are excellent. It is not the DD concept, it is the implementation that may be blamed. There are also some serious DDs that have no clocks and PLLs (e.g. Dual)
My thoughts when splitting hair for technology sake:
Sprung subchassis TTs are very hard to make right.
In addition to the static balancing and to dynamic balancing which if not done right give clear visible indications, there are other less noticeable issues.
Lateral, vertical and rotational compliance of the suspension allows and then tries to counteract the CCW reaction from the constant CW rotation of the platter, creating oscillations in the horizontal and vertical planes. These unintended movements in turn upset the attitude of the platter axis, causing rolling effect due to precession.
Rigidly attached, mass loaded and damped TT chassis have more chances to function correctly and predictably and they are easier to be built.
George
PS. I measured the TD-160 platter again using a vernier caliper and taking note of some constructional details, if anyone is interested…
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Frankie boy (fast42), if you've been hiccuping the last two days, I'm the culprit.
I've been listening to my AR94 speakers and wondering at myself. I realize now that it was really never about them, but about the rest of the system. They are far more revelaing than I remember them from 12 year ago, but then my entire system has changed, and most notably my power amp. At the same time, I am delighted not only with that, but just as much with the fact that I seem to have hit the nail on the head with the upgrading of the power amp. Completely recaped, but the two main capacitors were changed from a dual concentric 2*12,000 uF/56V by Elna to separate milk cans by BC Components (ex Philips) of 2*22,000 uF/63V.
Normally, just recaping an amp with fresh 'lytics will produce a positive difference, after all, that dual concentric measured at 7,200 uF, less tha half of its nominal value, and now it has +86% of nominal value. Forunately, that's all it took, everything else on the original PDU was so overrated this was no problem. And I have no better test bench for it than the AR94, which are nominally 87 dB SPL efficient, but do have nasty crossover characteristics. They kill most standard fare pretty dead if you turn the volume up. Now, the Marantz doesn't seem to even notice it.
At the same time, while delighted that the 94s are better than I thought they were, I also realize that they are no match for my own speakers, which have much better low and high ends. Different concepts (AR is acoustic suspension mine are bass reflex), which are comparable in the midrande only, where the ARs still do a great job. But their bass lines are not as deep as with my speakers, and lack its bass authority and pure gravitas, taken the bass line "size", when bass lines seem to have a greater size, sounding big and well controlled, whereas the ARs come across as veryclean and well controlled, but appear to be more "shallow", with much less authority.
Not complaining, mind you, just noticing the differences.
I've been listening to my AR94 speakers and wondering at myself. I realize now that it was really never about them, but about the rest of the system. They are far more revelaing than I remember them from 12 year ago, but then my entire system has changed, and most notably my power amp. At the same time, I am delighted not only with that, but just as much with the fact that I seem to have hit the nail on the head with the upgrading of the power amp. Completely recaped, but the two main capacitors were changed from a dual concentric 2*12,000 uF/56V by Elna to separate milk cans by BC Components (ex Philips) of 2*22,000 uF/63V.
Normally, just recaping an amp with fresh 'lytics will produce a positive difference, after all, that dual concentric measured at 7,200 uF, less tha half of its nominal value, and now it has +86% of nominal value. Forunately, that's all it took, everything else on the original PDU was so overrated this was no problem. And I have no better test bench for it than the AR94, which are nominally 87 dB SPL efficient, but do have nasty crossover characteristics. They kill most standard fare pretty dead if you turn the volume up. Now, the Marantz doesn't seem to even notice it.
At the same time, while delighted that the 94s are better than I thought they were, I also realize that they are no match for my own speakers, which have much better low and high ends. Different concepts (AR is acoustic suspension mine are bass reflex), which are comparable in the midrande only, where the ARs still do a great job. But their bass lines are not as deep as with my speakers, and lack its bass authority and pure gravitas, taken the bass line "size", when bass lines seem to have a greater size, sounding big and well controlled, whereas the ARs come across as veryclean and well controlled, but appear to be more "shallow", with much less authority.
Not complaining, mind you, just noticing the differences.
Frankie boy (fast42), if you've been hiccuping the last two days, I'm the culprit.
I've been listening to my AR94 speakers and wondering at myself. I realize now that it was really never about them, but about the rest of the system. They are far more revelaing than I remember them from 12 year ago, but then my entire system has changed, and most notably my power amp. At the same time, I am delighted not only with that, but just as much with the fact that I seem to have hit the nail on the head with the upgrading of the power amp. Completely recaped, but the two main capacitors were changed from a dual concentric 2*12,000 uF/56V by Elna to separate milk cans by BC Components (ex Philips) of 2*22,000 uF/63V.
Normally, just recaping an amp with fresh 'lytics will produce a positive difference, after all, that dual concentric measured at 7,200 uF, less tha half of its nominal value, and now it has +86% of nominal value. Forunately, that's all it took, everything else on the original PSU was so overrated this was no problem. And I have no better test bench for it than the AR94, which are nominally 87 dB SPL efficient, but do have nasty crossover characteristics. They kill most standard fare pretty dead if you turn the volume up. Now, the Marantz doesn't seem to even notice it.
At the same time, while delighted that the 94s are better than I thought they were, I also realize that they are no match for my own speakers, which have much better low and high ends. Different concepts (AR is acoustic suspension mine are bass reflex), which are comparable in the midrande only, where the ARs still do a great job. But their bass lines are not as deep as with my speakers, and lack its bass authority and pure gravitas, taken the bass line "size", when bass lines seem to have a greater size, sounding big and well controlled, whereas the ARs come across as veryclean and well controlled, but appear to be more "shallow", with much less authority.
Not complaining, mind you, just noticing the differences.
I've been listening to my AR94 speakers and wondering at myself. I realize now that it was really never about them, but about the rest of the system. They are far more revelaing than I remember them from 12 year ago, but then my entire system has changed, and most notably my power amp. At the same time, I am delighted not only with that, but just as much with the fact that I seem to have hit the nail on the head with the upgrading of the power amp. Completely recaped, but the two main capacitors were changed from a dual concentric 2*12,000 uF/56V by Elna to separate milk cans by BC Components (ex Philips) of 2*22,000 uF/63V.
Normally, just recaping an amp with fresh 'lytics will produce a positive difference, after all, that dual concentric measured at 7,200 uF, less tha half of its nominal value, and now it has +86% of nominal value. Forunately, that's all it took, everything else on the original PSU was so overrated this was no problem. And I have no better test bench for it than the AR94, which are nominally 87 dB SPL efficient, but do have nasty crossover characteristics. They kill most standard fare pretty dead if you turn the volume up. Now, the Marantz doesn't seem to even notice it.
At the same time, while delighted that the 94s are better than I thought they were, I also realize that they are no match for my own speakers, which have much better low and high ends. Different concepts (AR is acoustic suspension mine are bass reflex), which are comparable in the midrande only, where the ARs still do a great job. But their bass lines are not as deep as with my speakers, and lack its bass authority and pure gravitas, taken the bass line "size", when bass lines seem to have a greater size, sounding big and well controlled, whereas the ARs come across as veryclean and well controlled, but appear to be more "shallow", with much less authority.
Not complaining, mind you, just noticing the differences.
Attachments
Nice hiccup from you as well, my dear chap, two posts on it, 
!
Yes, the upgraded power supply is allowing the Marantz to drive the nasty dip in the crossover impedance with more authority, better current delivery. With regard to the high end of the AR94, have you tidied up the crossover feeds to the treble driver? As in, completely hardwired, and a nice, fresh, blocking cap,?
! Yes, the upgraded power supply is allowing the Marantz to drive the nasty dip in the crossover impedance with more authority, better current delivery. With regard to the high end of the AR94, have you tidied up the crossover feeds to the treble driver? As in, completely hardwired, and a nice, fresh, blocking cap,
?Here is something to think about. Set a TD160 or old style LP12 / RD11 / AR / Systemdek on a variac . Lets say go between 60 and 100 V at the motor ( possibly 180 to 240 V ). Being synchronous the speed variation should be below audibility at < 0.1 % . The sound you will hear will be dramatically different. So much so as to say is it the same turntable? At 60 V the sound should be very neutral but week. At 100 V gutsy but coloured.
This points out something very valuable. Things that are so small are clearly heard. What it is probably saying is the leading edges on the vinyl is mildly delayed and probably the peak causes a wobble? And yet the average speed is the same. That's the problem about hypothesizing the macro effects and not realizing that is 1% of the design problem. I say 1% as we have so many examples to copy. Why reinvent the wheel? The belt is not innocent. We do our best on that, motor voltage is the easiest experiment. A 10 V Buck boost transformer is a very cheap solution. A 9V 6VA will do fine. Wire 0V to live should give + 10 V . Wire 9V to live should give - 10 V. A 9 V 6 VA usually gives about 10 V on a light load.
How long a platter spins for means mostly nothing. If the bearing point is less than perfect that is rumble and the type that sounds awful. Motor rumble is not too bad, chaotic rumble is like very bad digital. If the shaft is damaged often that is not a great problem, seen as vertical lines or blurred rings. If it is polished in a pillar drill using metal polish it should be OK if the oil is thick enough. It is unusual this happens so not great advice, usually it is the point that goes. If the patter spins for a long time using thin oil that is actually bad. If the viscosity of the oil is higher and all is OK sometimes that is the route to a better turntable. The motor has to be able to offer the torque required if so. Rega did use EP 90. To check a bearing a thin oil is fine or even preferable, if it comes to an abrupt stop all is not well. As said before SAE 30 is not too bad. ATF also as it has no contaminates that matter. Verdier used Rocol lathe bed oil ( perhaps Ultra glide X5 ). I would guess olive oil could be used if changed every 6 months. Some use PTFE enriched oil . I have my doubts. Molyslip perhaps ( Linn black oil ? ).
Motor oils sometimes hurt bearings if they are phosphor bronze ( RD 11 , Garrard ). Not in motorcars as they use pressure bearings and the crystals do not form , phosphoric acid as confirmed by Esso research. Linn can have side wear whilst point OK. That is because PTFE is super hard as well as being super slippery. The hardness sometimes wins. Linn used it as it is acoustically opaque ( told by Logic not Linn ). In theory the oil makes sure the two never meet. That is theory and reality is different. The bearing precesses like a children's spinning top. Thorens machining on centres doesn't help when that ( TD124 ). TD160 is actually better and Dual are stunning on that ( even CS 505 ). Linn are concentric to 1/10 000 inch which is the limit. The bearing fit must not be too tight as that will instantly cause point failure even when 1/ 10 000 inch. Rega as simple as it is side steps the problems and for what costs less than £1 is very OK. Apart from being a bit narrow the Rega is a work of genius. The genius is setting up the tools to make it. It takes a week sometimes. When set 1000's can be made in very little time. The tool costs £200 but is a bar-lamb to get right.
If you tap a descending platter, one in PTFE and one in bronze. The PFTE is less resonant ( RD 11 and LP12 differ in that ). So all the shed engineers who say ah yes PTFE is a good slippery surface, not so as the clearance without oil is 1/1000 th inch. That's a Rizla paper all the way around. If you go tighter the bearing will not move with SAE 30 inside. Systemdek is loose. It has a spiral to raise the pressure whilst turning .
This points out something very valuable. Things that are so small are clearly heard. What it is probably saying is the leading edges on the vinyl is mildly delayed and probably the peak causes a wobble? And yet the average speed is the same. That's the problem about hypothesizing the macro effects and not realizing that is 1% of the design problem. I say 1% as we have so many examples to copy. Why reinvent the wheel? The belt is not innocent. We do our best on that, motor voltage is the easiest experiment. A 10 V Buck boost transformer is a very cheap solution. A 9V 6VA will do fine. Wire 0V to live should give + 10 V . Wire 9V to live should give - 10 V. A 9 V 6 VA usually gives about 10 V on a light load.
How long a platter spins for means mostly nothing. If the bearing point is less than perfect that is rumble and the type that sounds awful. Motor rumble is not too bad, chaotic rumble is like very bad digital. If the shaft is damaged often that is not a great problem, seen as vertical lines or blurred rings. If it is polished in a pillar drill using metal polish it should be OK if the oil is thick enough. It is unusual this happens so not great advice, usually it is the point that goes. If the patter spins for a long time using thin oil that is actually bad. If the viscosity of the oil is higher and all is OK sometimes that is the route to a better turntable. The motor has to be able to offer the torque required if so. Rega did use EP 90. To check a bearing a thin oil is fine or even preferable, if it comes to an abrupt stop all is not well. As said before SAE 30 is not too bad. ATF also as it has no contaminates that matter. Verdier used Rocol lathe bed oil ( perhaps Ultra glide X5 ). I would guess olive oil could be used if changed every 6 months. Some use PTFE enriched oil . I have my doubts. Molyslip perhaps ( Linn black oil ? ).
Motor oils sometimes hurt bearings if they are phosphor bronze ( RD 11 , Garrard ). Not in motorcars as they use pressure bearings and the crystals do not form , phosphoric acid as confirmed by Esso research. Linn can have side wear whilst point OK. That is because PTFE is super hard as well as being super slippery. The hardness sometimes wins. Linn used it as it is acoustically opaque ( told by Logic not Linn ). In theory the oil makes sure the two never meet. That is theory and reality is different. The bearing precesses like a children's spinning top. Thorens machining on centres doesn't help when that ( TD124 ). TD160 is actually better and Dual are stunning on that ( even CS 505 ). Linn are concentric to 1/10 000 inch which is the limit. The bearing fit must not be too tight as that will instantly cause point failure even when 1/ 10 000 inch. Rega as simple as it is side steps the problems and for what costs less than £1 is very OK. Apart from being a bit narrow the Rega is a work of genius. The genius is setting up the tools to make it. It takes a week sometimes. When set 1000's can be made in very little time. The tool costs £200 but is a bar-lamb to get right.
If you tap a descending platter, one in PTFE and one in bronze. The PFTE is less resonant ( RD 11 and LP12 differ in that ). So all the shed engineers who say ah yes PTFE is a good slippery surface, not so as the clearance without oil is 1/1000 th inch. That's a Rizla paper all the way around. If you go tighter the bearing will not move with SAE 30 inside. Systemdek is loose. It has a spiral to raise the pressure whilst turning .
I like number pattens. Here someone is claiming that Pi is mathematically an important number when the planet Mercury. Anyone care to look? I guess anything that rotates needs Pi? 365 to 88 ( ish ) days compared with Earth wouldn't have made me think of it. I was too lazy to find the 116 day pattern alleged.
The Illuminatus Observor: Mercury, The Key to Decoding the Philosopher's Stone
The Illuminatus Observor: Mercury, The Key to Decoding the Philosopher's Stone
Looking myself at least we know where 3180 uS comes from now. No wonder turntables sound good. Still think anything that turns will display ratios of Pi. If they didn't that would be odd.
If the Mercury ratio is more or less exactly Pi I think that doubly proves my point. If it is 0.1% out then highly curious.
If the Mercury ratio is more or less exactly Pi I think that doubly proves my point. If it is 0.1% out then highly curious.
You can't get pi by dividing any number by any other number - it is not only irrational but also transcendental (which means you can't get pi as the root of any finite polynomial).
I thought we always knew where 3180us (and 318us) came from? Surely the mystery is why 75us and not 79.58us?
I thought we always knew where 3180us (and 318us) came from? Surely the mystery is why 75us and not 79.58us?
Maybe they chose 75 uS just because 750 pF is a standard capacitor value.
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Yes 2kHz would be more logical . There were many EQ's that hovered around 40 to 100 uS. If you have passive EQ for the 75 uS a variable option is worth having ( Yes Nigel, time you did it ). Although not perfect to tweak the 75 uS alone it helps. When all three EQ's are correct the transformation is surprising. Often the old sound is just wrong sound. Also for the no tone control people it is one you are allowed to have. Mostly that's me as I seldom use them except when my OB speakers. Even then it is bass EQ only which is +16 dB 30 Hz ( only 8 watts at 30 Hz typical maximum ).
I just wonder if a number obsessive like me liked the idea of 1/Pi. 113/355 from my old Sinclair calculator kit I built. Circa 50/500/2124 Hz if RIAA. 7950 uS is best ignored. Squares in circles and outside of them .
Pi is almost 1.2 ( 1 + Thi ) Thi = ( root/5+1 )2.
Thi is
1/Thi 0.618033989
Thi 1.618033989
Thi x Thi 2.618033989
Thi x Thi = 1 + Thi
1/Thi = Thi -1
Thi power 10 = 123 to a good approximation.
power 11 = 199
Probably wrongly the number pattens of Thi always seems to suggest 10 is a good counting system and not 12 as I was told at school. That probably means I have never tried in a proper twelve number counting system 1,2,3,4,5,6,7,8,9,X,Y,10 .....
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Yes, there any many amazing infinite series that equal pi. One of the best is the Gregory–Leibniz series:
(pi / 4) = 1/1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11 + .........
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Isn't that totally beautiful.
This also . I don't know if it is correct. I think I see why 5 intrigued people and the church was less than enthusiastic. Hence me thinking 10 and more accurately 5 is a useful number of digits to have.
Thi = 1 – 2 cos ( 3 Pi / 5)
I imaging Thi can be written many ways. Or pronounced .
This also . I don't know if it is correct. I think I see why 5 intrigued people and the church was less than enthusiastic. Hence me thinking 10 and more accurately 5 is a useful number of digits to have.
Thi = 1 – 2 cos ( 3 Pi / 5)
I imaging Thi can be written many ways. Or pronounced .
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