Okay, let's go further. Do you think a special merry-go-round could be built for the little girl, so she could spin as many kids around as you can?
This goes to torque, and how one might approach building a turntable with a low torque motor, yet having mass applied so that performance would equal a turntable with a high torque motor.
I suppose the point here is that there are quite a few ways to skin the proverbial cat. |
As to Dover's post, belt creep is not caused from stretching the belt. Find Mark's writing on the subject because he explains it far better than I ever could, and he backs it all up with the proper math. It is a physical limitation of a belt drive system that generates an inherent tracking error.
As far as I know, Mark doesn't address tape drives or string drives, however. I don't look at a string drive the same way as a belt drive, but tape may be a viable way to avoid the problem. String drives have a limited slip that has always intrigued me.
Syntax discounts the idler drive out of hand, but I assure you that all the problems that he mentions have been addressed. It has a lower tracking error than a belt at around one part per million, and it has fewer maintenance worries than a string. Not only that, but with a proper controller it is more speed accurate. However, that's not to discount the string because I believe similar outcomes can be reached with a string when the system is designed correctly and built well. It can be fiddly, though.
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Hi Dover,
I stand corrected, I think. This is where I got tripped up on your post with the word "and" being key. "I said it is an assumption and that if the belt doesn't stretch then there is no creep."
More from Mark Kelly:
"Some form of tensioner (always on the "non-drive" side) will eliminate slip, but it won't touch creep.
Creep is necessary for a belt drive to work. The mechanism of creep is how the belt transmits force from the pulley to the platter, so no creep = no rotation."
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"These things all come down to the quality of the implementation, whatever direction is chosen."
Exactly. :) |
Syntax,
I may be even more cynical than you! I believe the overwhelming bulk of merchandise made is created mainly for profit, with the case being the part which receives the most attention. For example, one very famous turntable maker that almost everyone has heard of uses a $56 AC motor, and that's assuming you buy one, not a quantity. Well, we bought six of them, and they all cog an unbelievable amount. Even worse, spindle diameter wasn't at all consistent. The bottom line here is that some manufacturers build only for price points and marketing spin, yet audiophiles continue to eat it up.
However, I also know of manufacturers who live audio, and for them expanding the art trumps anything else, so hope springs eternal because they manage to find like minded customers.
We'll survive! :) |
Sksos1,
I think we all know which one you will put at the top of that list!
Seriously, such a list would be surprising to a lot of people, and it would undoubtedly generate angst among many manufacturers, not to mention all the explanations from end users claiming the results are from someone with an axe to grind, or it was just some unlucky random sample. Whatever, the thread would probably become Flame City right away.
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Halcro,
Yep, but that won't happen. A lot of new ones pass, but the surprise is which ones.
Some old ones don't pass, however. I built a DIY turntable around eight years ago that started life as a Lenco. It runs a little less than 1/4 RPM too fast no matter what I do, so after a frustrating hour wasted I quit tinkering with it. I could never get the wheel placed accurately enough to correct the issue, as minor as it may be. It's dead on according to the KAB Speedstrobe, so I suppose it is close enough. Maybe I'll revisit it someday.
The real problem is with those turntables out there that do not keep a consistent speed. It is one thing to have an ever so slight speed issue that is evenly paced, but quite another when it varies, especially if it varies abruptly.
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I have checked a few, but mostly I have checked motors that are commonly used. I was surprised. |
The timeline has a quartz clock. It is accurate, according to Ron Sutherland, of two parts per million. That's very good, and I have no reason to doubt him.
I don't know the limits for other drive types, but it is theoretically possible for an idler to be accurate to around one part per million, so my controller was designed for that. You could go further with a GPS referenced OCXO clock in the controller, but could anyone hear it, and could the device keep up with the clock?
At some point we have to question the merit of it all because there are mechanical limits. And, just because a turntable has a great clock doesn't mean the turntable spins accurately, and just because it spins perfectly in the lab doesn't mean it will do it under every condition, in every environment. Still, I believe it is the responsibility of a manufacturer to get as close to perfect as he can given the price point of the machine he is selling. If you pay small money, you aren't going to get super accuracy, but you may get a very musical turntable that is consistent. To me, that's worth a great deal, although I personally try to push the limit to its threshold. Essentially, you should get what you paid for.
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I made an error in my last post. The Timeline is accurate to one part in two million. |
Dover, your post leaves me with a lot of questions, but I won't go there. However, there is a need to explore torque and inertia. They can be confusing terms. Explained in the very most simplistic way possible, torque is what you need to get the platter spinning, and inertia is what you need to keep it going smoothly.
So, it is possible to get very good results with a very low torque motor because you can still have good inertia. The downside is that the turntable will reach its speed much more slowly, assuming the platter is a heavy one.
You can have both high torque and high inertia, but there is usually a price to pay. That price is motor size and lots of heat generated by it. Ashland was noted for making such motors, and quiet ones at that. The one used in a Fairchild 750 studio machine is the size of a clothes dryer motor, and it runs very, very warm. So does the more common one found on some Rek-O-Kut turntables and the Canadian made McCurdy. I would be happy with either motor in the Saskia, but they are no longer available.
By comparison, we are stuck with lower torque motors, if we want great precision, but we can still have lots of inertia. This is where system design comes into play, and done right a design can greatly benefit speed accuracy.
I suppose the point here is that most turntables, if not all, are compromised to some degree, however small. The trick is in making certain that any of those compromises do not negatively affect the end result. Hopefully, reliability and looks aren't affected, either. It isn't as easy to accomplish as you might think. Such an undertaking requires a lot of thought.
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...unlike my clunky grammar which required zero thought. :D |
From Dover's post, "The point I take from your Goldmund example is that you are suggesting that mass alone will not provide stability with a motor that simply doesn't have enough torque to start with."
Let's think about this for a minute. Is the platter solid? Where is the bulk mass located? If the platter is solid, most of the mass is toward the outside, correct? Is that where it should be? One would assume that it should be because almost all turntable platters are made that way. But, it it really the right way to design a platter, regardless of the drive type?
Now, let's make some analogies.
1) You have a playground merry-go-round with six kids on it. They are positioned towards the outer rim.
2) You have a playground merry-go-round with six kids on it. They are positioned, so that the merry-go-round is perfectly balanced from center to edge.
3) You have a playground merry-go-round with six kids on it. They are positioned as close to the center as possible.
All the kids and all the merry-go-rounds weigh exactly the same. Which merry-go-round is easiest to control, if you are the guy pushing it? Would a scenario exist where it be possible for a small girl push one of them, but not the others?
I submit to you all that platter design is the most seriously overlooked aspect of a turntable. Location of mass matters, and it matters a lot. I consider the platter to be more key to the sound of a given turntable than drive type, or speed accuracy for that matter.
Disclosure: I manufacture idler drive turntables with speed controllers.
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Ct0517 and all,
Yes, I am familiar with Verdier's work, and admire I it. I am puzzled that his bearing doesn't seem to be in keeping with his papers, but I suppose that is a topic for another thread, not that I would say anything critical about Verdier because he did think outside the box. Verdier, Mitchell Cotter and others have written at length regarding the practical application physics in audio. If anyone thinks we are fumbling around in the dark now, I cannot imagine how it would be without men like them to at least challenge us to reach higher. |
Lew,
You you may be right. I spoke out of school because I lack the extensive firsthand experience that you have.
Thuchan,
You are right.
Lawrence,
I took no offense, but you haven't heard them all, and I'm here to say that an idler can be made that can do anything the others can do. I am sure of it.
Now, if I can only convince Syntax. Then, the fight will be won! That will certainly take some convincing, won't it? At least he and I agree about string drive! ;)
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Richard is dead on with his post, in my opinion. Our ears are critical for good reason, so let's go back and take a look at the thread as its originator intended. It is about the three different drive categories, assuming the string isn't in one all its own.
Direct drive:
How well it works depends upon how its speed is controlled and how it is coupled to the platter. Of course, there are many other variables, but these are most critical for this drive method. I believe a great direct drive is the most difficult to achieve because of audible artifacts introduced by most implementations, but some have accomplished the task beautifully. The Mitchell Cotter turntable comes to mind instantly, but others, like Brinkman have done an admirable job. Still, my ears hear a lack of dynamics and a "jitter" with 90% of the direct drives out there. One thing I have noticed about them is that the plinth isn't quite as important as it is in other designs. That's probably due to how the spindle is coupled with the rest of the system. It is a system that can be stellar, but it is difficult to do.
Belt drive:
As we all know, these run from horrid to fantastic. It seems that most are copies of another one, in that they typically use essentially the same motors and same belt treatment, more or less. Others, however, employ ingenious workarounds to avoid any pitfalls introduced by belt creep. The SG Spiral Groove comes to mind with how the motor is oriented to the platter. There is very little spare belt hanging out there in air with that turntable. That differentiates it from the pack, and the results show it. That's only one example, but I gave it to illustrate that there are designers who build belt drives who think outside the box in extremely practical and creative ways. There are others, but most go down the path of the status quo. Anyway, I believe we will see a lot more done with belt drives because there are a lot of ideas that haven't been tried, yet. There are also ideas that have been tried, but forgotten for some reason. Possibly the finest belt drive I have ever heard is the Fairchild Studio 750. This old beast went against convention by using an incredibly high torque motor. Maybe someone will repeat that with a modern incarnation. Even if they don't, great belt drives exist in fairly large numbers.
Idler drive:
I realize that idlers are foreign in many circles, and that biases exist which are based upon vintage units that display what appear to be inherent weaknesses. Most of those weaknesses, however, are due to resonating linkage, clunky top plates, noisy idler wheels, etc. One thing to bear in mind is that the idler wheel tracks with greater inherent accuracy than a belt. The trick is to make it track quietly, which can be done. If one eliminates the noise of the vintage units by totally rethinking how the technology should be applied, an idler can be a wonderful turntable.
So...
Any of the three can be at the top of the food chain. It all depends upon how the design is approached and how practical ideas are implemented that improve on what was done before. We will never settle the discussion of which is best, as long as people fail to realize that drive methods are nothing more than points of departure, and that the devil is in the details, regardless of the method chosen.
I submit to you all that turntables exist, or can be made, of all three methods that are high performers, and that those turntables can satisfy anyone's personal preferences when the problems facing each drive discipline are addressed properly.
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Ct0517,
I probably hear the same things that Richard hears, or more appropriately, I miss the same things that Richard misses. Mainly, dynamics suffer. Some dynamic information is missing, and micro dynamics are smeared. Subtleties in the high registers and midrange seem clumped together a bit. It can be difficult to notice at times unless you are very familiar with the music, but it really apparent to me with well recorded piano pieces. Transients suffer, in particular. I will say that I could possibly live with some of the machines that are flawed because some are better than others. Still, it is there. We are getting somewhat nit picky, but that's what high-end is about, right?
Like Richard, I have a commercial interest, so bear that in mind. You may want to carefully make some comparisons for yourself, however. I believe you will hear it, especially if you have the opportunity to make some A-B comparisons. |
Tonywinsc,
In answer to your question, it's my opinion that it could be any of those things you mention. If I heard it, I might be able to tell, but it's impossible to say from here. It is too bad you don't have the luxury of trying several tables, arms, etc. in your system. Then, you might be able to make a determination. It could be the record, you know? |
Richard,
Regarding R&D for my turntable, it is expensive. In fact, it is so expensive that I will probably never recover the costs. The time I tossed $1500 worth of spindles into a trash barrel comes to mind, as does the seemingly endless controller revisions. Don't expect me to forget the 79 NOS motors I bought, either! Was it worth it? Yep.
I learned the hard way, but I suppose that's how it is with most small manufacturers. R&D isn't just about buying stuff and making parts, however. It really is about learning. You think you don't know anything, and then you realize that you have been eating and breathing it for a decade, so you must have picked up something along the way. That's how R&D works; it's incremental.
Most small start-ups can't afford big time R&D, so their approach may be different from the Panasonics of this world. For me, it involved reading countless white papers that others had written. It involved making purchases of numerous vintage turntables just to see what makes them tick, and it included observations of other machines outside the audio realm. It goes on and on, and it is as much passion driven as anything else. When it is all said and done, I hope everyone who owns one of my turntables will enjoy it for a lifetime. My goal is to make a turntable for my personal use that I don't want to upgrade. Then, it's finished.
Ketchup,
I have a controller to run my turntable, too. Is it laboratory grade? I suppose so, but I never thought about it in that light before.
I suppose calling it an audiophile grade controller would have been better, but nobody would be impressed in the least with a name like that. I honestly don't know what it should be named because it will have followers and detractors, no matter what.
A story...
My friend, Dave Slagle, has been working with strain gauge cartridges ever since I have known him. Not too long ago, he developed a new type drive for them, and he built one for me. He didn't provide a power supply for it, though. So, another friend gave me a laboratory grade power supply to run the thing. It says right on the panel "Lambda Regulated Power supply", and that's a known laboratory grade one. Does that make me happy? Well, I'm waiting for that genuine Dave Slagle audiophile grade one to appear at my house. It just goes to show, you can't please everybody no matter what you do. :)
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