The type of lubricant depends on the type of bearing. I would stick with what the manufacturer uses.
Showing 11 responses by herman
El, it has to have some amount of cogging, otherwise there wouldn't be any need for the sensors. Every time it makes a correction it cogs and with an off center record it would be doing so continuously. Of course it is another matter whether this detracts from the sound. I'm curious where the sensors are mounted in relation to the pivot point. Your spec of .05 degrees seems like an awfully low figure. With a 3 inch arm that would be about 70 microns at the stylus. I'm not saying it can't be done, but that does seem awfully low for a consumer table. While I agree that it is an interesting exercise in engineering, one has to wonder why nobody builds such a system anymore. In the cost is no object world of high end audio things like stepper motors, hall effect sensors, and microprocessor controllers are dirt cheap. Perhaps it is a matter of perception given the amount of trashing they took early on. |
Those of you who recommend a particular lubricant as ideal for all spindles are simply wrong. Look at your car. Why do we use one thing in the motor, something different in the transmission, something different on the wheel bearings, and so forth. Sean, the link you posted above even points out that the type of test used was applicable to engines but not to other situations. The type of materials at the pressure point, the shape of this point, the amount of pressure on it, the tolerance of the machining, whether or not it is inverted, and many other factors all play a role in what constitutes the ideal lubricant for a spindle. The bottom line is that this is NOT a one size fits all situation. Deviate from the manufacturers recommendations at your own peril. |
Sean, I believe it is a bit more complex than just choosing a lubricant based on how slippery it is. From the Teres website: "The bearing is designed with large amount of surface area to maximize viscous damping. The oil in the bearing exerts a smooth, constant resistance as the platter rotates adding to speed stability." Evidently they want a certain amount of drag. Don't you think the amount of viscous damping is dependent on the type of oil used, and that they chose one to achieve the desired result? If the wonder oil you tout reduces drag to too low a level then the bearing would not be doing what it is intended to do. Why does VPI recommend lithium grease? Perhaps for the same reason. In any case, it is inconceivable to me that a company such as VPI would recommend lithium grease if a lighter weight oil would be better. Surely they have looked into this a little deeper than your average audiophile and come up with what they feel is the best lubricant for their turntables. The "slipperiest substance known to man" is not always the best stuff for a particular application. |
Sean, I'm suprised to see this side of you. Now that you have been proven wrong, you've decided to go on the attack labeling designs that deviate from what you consider to be proper as "piss-poor?" If the platter rotates at a constant speed and continues to do so for a long period of time then it is a good design, case closed. It doesn't make one bit of difference how the final result is achieved. So I'll go back to the original question and try to make my point once again. The folks at VPI, Teres, Linn, Basis, etc. have dedicated countless hours to optimize every aspect of the performance of their tables. I believe it to be highly unlikely that you can improve that performance by using a lubricant other than the one they recommend. |
Sean, while I respect your opinion on most matters, after looking into this a little more deeply, just about everything you said turns out to be wrong. Your diamond cutting glass analogy makes no sense. The stylus isn't "slicing" through the vinyl, it rides along the surface following the modulations already cut into it, and just because the stylus is harder than the vinyl doesn't mean there isn't any friction. It is well documented that the stylus temperature can easily reach in excess of 100 degrees celsius. Where do you think that heat comes from? I'm guessing friction, and the drag caused by that friction must be dealt with. You are also confused about the differences in viscous damping and friction. "Friction is the enemy of any well designed product that requires motion. After all, friction generates more heat, causes more wear, requires more force and is nothing more than lost energy." Viscous damping is not causing the bearing to wear away. Your idea about instantaneous speed correction is completely incorrect. The motor doesn't and can't correct for every tiny variation in speed that would be caused by the stylus and there isn't a turntable in the world that uses the motor controller to do this. It won't work for the same reason that motor driven, servo controlled linear tracking tonearms won't work. With the tonearm you are constantly trying to correct for something that has already happened so the arm is always out of postion. Same thing with the system you advocate. Even if you could build a controller fast enough to keep up, in order for it to compensate for the variations in stylus drag it would have to be able to predict when they will occur, and that's not going to happen. So how can you overcome these variations in drag caused by the stylus when you can't predict when they will occur? One way is to introduce another source of drag into the system (such as viscous damping) that is far greater than the stylus drag, and while the motor is working to overcome this induced steady state drag it will in effect ignore the tiny variations caused by the stylus. To use an electronic term you may be familiar with, they are swamped out. This is not poor engineering. It is a brilliant, simple, elegant solution to the problem. |
Sean, your seeming inability to even hint at the possibility that you might be wrong makes it impossible to discuss this in a logical manner. I'm leaving the topic after this. First you claimed that the stylus was "slicing" through the vinyl like a diamond cutter through glass. When I point out you are wrong because it is "riding along the surface" you change to "scraping," which is in effect exactly the same thing I just said, and make a condescending remark like I don't get it. You should go into politics. The heat isn't generated simply because the stylus isn't centered. It comes from the stylus tracking the modulations. Heavily modulated grooves produce more heat than lightly modulated ones no matter how well centered the stylus is. Centering has nothing to do with it. This is a well proven fact, not an opinion. You are wrong. No matter how many times you put forth the centering argument, you will still be wrong. Also, there isn't a manufacturer in the world that uses a servo motor controller to compensate for instantaneous stylus drag. Why? It won't work. No matter how fast, servos will always be reacting to something that happened in the past. Again, not an opinion. It is a fact that you are unwilling to acknowledge. All servo controlled linear arms to date have been inferior to other designs for the same reasons. This is also a fact. I do believe given the advances in servo motors since the attempts in the early 80's, and the speed of todays microprocessors, that it should be possible to build one that will work well. Perhaps combining the tracking capabilities of the newer laser tonearms as the feedback to the controller along with high speed processors might work. The laser tracker could be positioned ahead of the stylus, in effect predicting where it needs to be instead of reacting to it being where it shouldn't be. Feel free to use and develop that idea. |
El, I'm not familiar with your table but once had a Technics linear table with direct drive and a motor driven linear arm. They were all the rage back in the early eighties but fell out of favor with the high end crowd after proponents of belt drive platters and conventional pivoted arms convinced us that the former were inferior because the direct drive motor was always searching for the proper speed and the arm was crab walking across the record. Maybe it's true and maybe not, but as far as I know they did disappear from the market. I do believe the best linear arms are capable of better peformance than the best pivoted arms. If they could just get the cost down to where I could afford one. In my price range I think the pivoted arms are superior but I'm not sure what all is out there in the linear world. Everything I see is in the $10,000 plus range. |
El, one of us is confused and I think it is you. Consider a record where the spacing is wider than average. You lower the stylus into the groove, the arm is perpendcular to the rail, and begins moving toward the spindle. However, it is traveling too slowly for the wide groove spacing and soon finds itself lagging behind. The sensors see this and before the arm can get more than .05 degrees away from perpendicular the arm speeds up momentarily to recenter. It just cogged over. This will continue all the way across the surface. Consider an off center record. From the point of view of the arm, the off center record presents a groove that is on average moving toward the spindle, but also constantly wandering back and forth. So to maintain the perfect angle the arm sometimes has to speed up when the grove is wandering toward the center and actually back up when it is going the other way. The pivot will allow the arm to move back and forth with the groove to a certain extent, but when the angle approaches .05 degrees it will cog. The only way for your table to keep the arm at the perfect angle is to know in advance which way the groove is going. It doesn't. It senses when the arm is not centered and then reacts to this. If the arm was tracking the groove perfectly then there would be no need for it to pivot and no need for sensors. The very fact that it does proves that it is not always at the perfect angle and cogs to correct anytime the arm approaches an angle of .05 degrees. I'm not saying it overshoots. I'm saying that Sony biases the arm to move at a rate that will track the average record, and that any record that is not average will require the arm to cog. |
El, eplain to me how your arm can keep from cogging over to catch up when the groove spacing is wider than average. You can't. If the arm is moving at a constant speed and the groove's relative motion toward the spindle is faster, the arm has to either make periodic corrections or keep getting further and further behind. Either we're talking about 2 different things or one of us is wrong. These aren't the "problems of slipshod design." They are the issues that any arm has to deal with. I'm not saying that your system might not be the best solution to the problem, but to deny that it exists is ludicrous. Sean, I don't think my example of an off center record is extreme. El tells us his sylus won't deviate from the center line more than .006 inches. That is less than 1/128 of an inch, about the width of the markings on my ruler. Not much. I just tried a number of random records and several of them were easily moving back and forth more than 1/128 of an inch. Since it pivots it can track deviations up to the .006 limit without any correction. After that it is either making corrections or it is deviating more than .006 inches. You can't have it both ways. |