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76.168.68.144
".... Rock Solid Speed Stability ...."
Teres has been struck by lightning on the road to ......... Rim Drive.
You can't call it Idler-- 'cause there's no intermediate wheel, and it does have electronic speed-control, but--- hmm. Well, now.
You say direct coupled rim drive, huh ?
I think we've been talking about that here for quite some time.
This is a sea-change in the thinking of the enormously influential beltdrive manufacturer. And they're not putting out tentative feelers, here, either.
In fact, this "motor supercedes our current Reference motor and is now the standard motor for all Series 300 turntables .... and is highly recommended for all Teres models."
Who's next.... Clearaudio ?
Birch ply, anyone ? Can we talk glue ?
J.D.
Follow Ups:
Art Dudley in Stereophile a few months ago stated that with his Linn table moving the motor so the pulley is parallel to the cartridge was an improvement.
I believe the reason given (or I might have inferred this, don't remember) is that when the motor is in a non-parallel position it is pulling the platter to the side. The platter is also trying to restore itself to its original position resulting in a wobble. When the pulley is parallel to the cartridge the same thing happens but the azimuth should be more constant. Don't know what the consequences to the sound are of the platter moving back and forth.
The wobble must be very small but I don't believe I've seen this issue discussed before.
With the Versus it looks like you can move the motor around the platter very easily. I wonder if there is a "sweet spot" for the motor where it might sound best because of minimizing the wobble effect? The results of such an experiment might be useful for any vinylist that can move his motor.
Here is a link to the Linn mod that one of our AA members did:
The difference in azimuth must be so tiny that I don't think it is a practical problem unless there is a major play in the bearings. Flattening the LP itself to +/- 0.1 mm precision should improve things much more.
I believe, the belt tension sort of negated that, but apparently I've been wrong (I'll have to think about it some more and experiment a bit).
In the case of the TNT eaerly versions had the tripulley which was intended to center the platterand prevent it from wearing n one side only. It eventually got dropped becaue in 'floating the main bearing the platter had slight 'shifts' between the contact points which blurred the sonics. I had a Tripulley and greased the bearings, with very good results sonically, the equivalent of running a single pulley in my experience or, at least, very close to it, although I did have to crank up the motor controller!
I can see now, though, that I may have mistakenly placed the azimuth fluctuation over the VTA fluctation in importance. I appreciate you pointing that out.
Stu
I recall reading in one of the magazines that the tri-pulley system was dropped by VPI because the noise that it introduced into the system outweighed the centering benefit, and also because the newer-style inverted platter bearing did not benefit from the centering effect.
The pulleys on the tripulley were a bit, ah, loose, with noticeable rattle if you applied pressure to them laterally. Greasing them up really tightened up the sound and I actually prefered them greased than with a single belt to the motor. It was a big issue on the Phonogram website.
I believe the chief issue in the creation of the tripulley was to eliminate wear on the main bearing due to belt tension being on only one side.
Stu
also use three motors in their top models. I was told by Clearaudio that the main reason was to center the platter/bearing.
To me it seems like overkill but I would like to think they tested it both ways and liked three motors better. That is also roughly three times the noise and my old Clearaudio motor was very noisy.
Anyway, with the Teres motor one can experiment fairly easily.
Without an intervening idler made of rubber, one of the drive surfaces has to be some grippy material like rubber. Unfortunately, the dimensions of a piece of rubber or something like it, cannot be machined so closely as metal or guaranteed of long periods of time. (I had a reel to reel tape recorder that never ran at the right speed because the drive capstan was made of rubber, and it had compressed or shrunk over the years.)
Now by putting an idler wheel in between the drive pulley and the turntable rim, you can machine the drive and the rim to close tolerances, and it does not matter if the rubber changes size a little.
So when they claim "The Verus controller technology establishes spot on speed accuracy that will not drift over time and never needs to be readjusted." there must be some feedback from the actual turntable to achieve this. If you just ensure the drive motor spins at the same speed forever, the table will change speed as the rubber wears and compresses. I'm sure it'll stay close enough when it's new, but as it gets older, the speed will change.
But they say it can be fitted to other tables, so how do they get the necessary feedback? They probably don't, and just let the speed slowly change over time.
-----------------
The Teres belt drive motor controller gets feed back from an optical sensor in the base of the turntable that reads a strobe pattern imprinted on the underside of the platter. I do not know if the sensor will plug in to the Verus but that is how it was done with the belt drive.
I believe the Verus' O-ring is easily replaceable, so there shouldn't be an issue with rubber wear or compression. No doubt there will be lively debates on the sonics of various O-ring compositions (urethane, polyacrylate, etc.)
Good to see they are finally going to an AC Synchronous motor, always said they sounded the best no matter how they are formatted. Not sure about the rim drive though. Call me in 10 months and tell me about bearing wear on the motor shaft. Made one on a Scout, sounds great but very different, not my cup of tea but that's what makes all of this interesting. I think a platter run by a rim drive flywheel would be SOTA and could be design friendly for minimum bearing wear.
HW
Sorry HW, but the Verus motor is nothing like a single phase AC motor.
The side load on the motor bearing is about the same as with a belt drive so bearing wear is a non-issue.
Chris, it's not the way the motor is built (one phase, three phase) it's the lack of a feedback loop that makes an AC motor sound so real. A DC motor knows where it was, an AC motor knows where it is. No amount of hyperbole will change that.
I have personally had over 20 reel to reel decks in the last 30 years, every capstan wore out due to side load, another item that cannot be changed. I have turntables running 20 years that are still within spec due to the belt drive.
While we are at it let's retire another ploy I keep hearing about. The non-stretch belt is not optional on a DC motor, without it the speed is all over the place from microsecond to microsecond. The loop sees belt stretch as a speed change and will attempt to correct. An AC motor simply requires a clean accurate signal and it is unaffected by the outside world. Make your belt right, your bearing right, and know how to set up a table and you will have dynamics that a DC motor dreams about.
I have never loved the sound of DC motor tables, could I live with one, absolutely, if an AC one of the same quality was not available. I've heard one of your tables driven by one of my HR-X motor flywheel assemblies and it sounded really wonderful (you should probably hear one). I have a Micro-Seiki DDX-1000 driven by an HR-X motor assembly. It too sounds significantly better than the original DC DD motor.
I understand what you hear in the direct rim drive (I have a Scoutmaster set up like that), I'm just worried about long term stability and customer headaches. HW
HW, I agree that the synchronous characteristic of an AC motor is inherently superior. However, a single phase AC motor by definition will have a great deal of torque ripple (cogging). DC motors will typically have an order of magnitude less torque ripple which is also highly desirable. So it comes down to compromise.
On the other hand our Verus motor has less torque ripple than even our DC motor and also the desirable synchronous characteristic. The low torque ripply allows it to be tightly coupled to the platter without detrimental effects. This way we get the best of both worlds.
The side load for a tape capstan is dramatically higher than with our rim drive. Like I said before it's about the same side load as a belt drive. I suppose it could be an issue but no more so than with belt drive.
You seem to be missing an important part of our DC motor design. The servo loop has a very slow adjustment algorithm that does not attempt to correct short term errors. So the issue of belt stretch does not apply.
Chris
As you will have noticed, you've captured the attention here of many analog-based enthusiasts. We'll be watching, some of us buying, as this all develops.
But one thing.
Your tech notes page keeps referring to " Direct Drive " as the name for your Edge-Drive product. Here your notes fairly shout :
Direct Drive, No Compromise
Since the Certus motor requires no isolation direct drive was selected for the drive mechanism.
Direct drive provides perfect coupling of the platter and motor and avoids the pitfalls and compromises inherent ...
Do you think, in the interest of clarity, that you could avoid using this term ?
For all I know, you may be able to make some kind of Clintonian case that your design merits the title of direct-drive. But.
As you can tell from this thread, there is already a fair distribution of strong opinion, not to mention disagreement, sprinkled amongst the few agreed-upon principles.
Up till now, "Direct Drive" is known to all as the type of drive that powers a turntable with motor On-Axis, generally with a servo'd dc motor, as in the standard Technics SL turntable.
Considering that Matsushita / Technics has untold millions of prior examples out there, couldn't you decide to call your turntable drive something else ?
Edge Drive, Rim Drive, etc, are all descriptive and accurate. You may not like those for some reason or other.
But it's like calling your new Gasoline Powered Super Car something like 'Super Diesel' --- to name this as you have.
Whaddya think.
J.
J.D.
You and some posters to this thread seem to be getting the Certus and Verus motors mixed up. The Certus motor is a true direct drive and has the motor on axis. Certus turntables were introduced last year and the motor is not offered separately. Also magnetic damping (eddy current brake) only applies to the Certus. The tech notes page was written only about Certus. It is being cited because most (but not all) of the information also applies to Verus. I am in the process of writing a new tech note that applies to both Verus and Certus but it is not complete.
Verus was born out our attempt to make the Certus technology more affordable. It uses the same type of motor but it is not direct drive. For the drive method employed with the Verus motor we coined the term "Direct Coupled". We could have called it rim drive, but the terms idler and rim drive have become synonymous. Verus is rim drive but it clearly is not the same as idler. It is also a more directly coupled than idler, hence the name.
As I've mentioned below, both your "certus" and "verus" seem to have claim to being the New & Optimal Thing, as far as teres is concerned.
And then there are the beldrives, which I'd assume aren't being abandoned either.
Honestly, you can't really have it that they are all better than each other.
Not wanting to put anyone on the spot, though, is it perhaps the case that the hype on the webpages is possibly premature and uhm, a little overlapping ?
J.
Contrary to all of the reactions this is much more about motors than it is drive mechanisms. It seems to me that a turntable drive design comes down to a balance between two competing objectives. Tight coupling of the motor and platter is a good. Motor cogging and vibration are bad. And the way to deal with the motor cogging is to provide isolation, and less coupling. So drive mechanisms are usually a compromise and the key to a good one is to get the compromise right.
If you have a motor with less cogging you can more tightly couple the motor and platter and get better, less compromised results. I submit that the key to success is to apply the right amount of coupling for a given motor. But it's the quality of the motor that dictates what drive mechanism will be optimum. For example using a typical AC sync motor with direct drive would produce terrible results. Not because the direct drive is bad but it's the wrong compromise for that motor type.
So our pursuit has not been so much about drive mechanisms but rather about producing low cogging, low speed motors that in turn allow for tighter coupling.
Here is the rub. Low cogging motors are both expensive and difficult to produce particularly if they need to operate at low speeds.
With that background here is how I see the hierarchy.
1) I believe that direct drive is king. It seems to be the best possible technology and results in the least amount of compromise. But it is the most unforgiving design and requires a superb motor to get top shelf performance. It's a path with a lot of pitfalls, I know cause I stepped in a bunch of them. Oh yes, be sure to bring your wallet because this is also a very expensive approach. With Teres price of admission starts at $13k.
2) Rim Drive is in my opinion the next best thing to direct drive. It offers some motor isolation but far less than a belt drive. Because of the limited isolation a low cogging motor is needed for the best performance. In my opinion vintage idlers suffer from cogging and noise problems. But the positives from superior coupling are for many compelling enough to outweigh the negatives. BTW, I am not talking about rumble. Rim drive is far less expensive than direct drive to implement and the demands on the motor are far less. With Teres the price of admission is $1690.
3) Good old belt drive comes in third for me. But it would be absolutely incorrect to say that I am not a fan of belt drive. Belt drive certainly has a place in high end audio. Belt drive is a very forgiving topology that works well with almost any motor. You can even use a rattly AC sync motor with a rubber belt and get reasonable results. But again it's about getting the coupling compromise right. A low cogging motor allows for tighter coupling even with a belt drive so it's still the same principle.
The Teres price of admission is $750.
So for me it's like cars. Because a BWM M3 has better performance than a VW Jetta it would be ridiculous to assert that Jetta's are junk, or to stop making Jetta's.
Thanks for the concise answer. I've gotta say there's not a lot of that around.
Rather than continue the grilling here-- there's inquisition & discourse aplenty left for later--- I suggest we all go toss something on the barbie & mix up something tall and cool.
Have a nice weekend, all.
J.
the response is almost guaranteed to disappoint the faithful!
LOL
No Guru, No Method, No Teacher
A sure sign of someone who has paid the necessary dues. Definitive text.
Rgds
J.D.,
Is the Teres technical article that you are referring to the one in the URL referenced below? If so, that article is discussing the Certus motor which is a direct drive. The Edge-drive or Rim-drive or Direct-Coupled motor is the Verus, not the Certus. I did not see a technical article regarding the Verus on the Teres website. Did you find one? If so, could you give us the URL?
Thanks for your help.
the many new revelations at hand...Sorry about that, you're definitely right.
But this brings up the question -- What's the ultimate Now ?
(Well, paradoxically, --Not belt--- we're fairly certain of that, from the info given.)Teres seems to be re-making itself and revealing newer New revelations on every page.
DC servo motors ? Definitely. Multi-phase ac-synchro ? Definitely.
Direct drive ? Definitely. Edge-drive ? Definitely. Belt-drive ? Hmf.
A little hard to know which end of the wave of hype will hit next.
Sorry again for mistaking Verus for Certus. Or is that mixing Truth for Certainty* ?
JD.
* old father rodney would be proud of me on that one
verus = true, real, proper, right.
certus = undoubted, certain, sure.
No .... I ain' gunna drop seventeen bills for a new/diff moto (even if I wanted to). [I'm just not that kind of girl :-)..]
And I'm waaaaay too lazy to lash up an infinite (monkey theory) layer birch ply rim driver. Even if I might actually prefer it?
P.S. Infinite Monkey Theory is not a slap at idler plinth builders. Nope. Was the name of a good friend's band. And is its only reason for inclusion in this post (glad we settled that Elmo).
Is it noon yet?
Good to see you're bearing up.
I can just barely recall a short story (was it Maugham ? Orwell ? Burgess ?) that began by rating the weather in the subtrops where our colonist hero dwelt :
as causing a man to reconsider how many Gins might well be appropriate before the jungle mists burnt off in the morning ....
Saw another great band name recently .. "Gratuitous Umlauts"
Nice.
J.
The cutting lathe that cut the lacquer most likely had speed fluctuations due to the drag of the cutting head during highly modulated passages. Unless your turntable also exhibits speed instability during these passages, the recording might not sound right.Producing a rock solid turntable in terms of speed stability seems like shooting yourself in the foot because the cutting lathe probably wasn't so stable. If it was, however, why not just build current "SOTA" turntables with drive mechanisms, bearings, and platters, similar to cutting lathes?
I mentioned this over on the Audiogon thread. It raised some eyebrows but got strangely quiet soon after.
link edited
..... , the most extreme examples would presumably be 12" 45's with monster groove excursions and bass.
It might be that part of the reason for their enduring popularity at clubs (putting aside the ability for the DJ to mix/fade/scratch "hands on") is that they actually have a considerable amount of 'speed' added to transient edges by the inversion of dynamic wow from the cutting lathe - "now with added PRAT!"
SO yes, it could be argued that a TT should "correctly" invert dynamic wow to be truly faithful, in temporal terms, to the recording.
Having said all that, there were some quite informed replys, and somebody who had actually worked with a cutting lathe reckoned that the size of the DD motors, combined with the mass of the platters on most cutting-lathes would result in no measurable (or more importantly, perceptable) dynamic wow........
In addition to the link below do have measurement plots of a Linn Axis, which look better than the LP12/Lingo. All plots (LP12, Pioneer PL1000, Linn Axis) can be downloaded from that thread.
The ultimate test should be done with a perfectly flat and centered record. Then one could look at the speed instabilitties of the recording itself and platter separately.
T
circuit such as the VPI SDS, or a Walker speed control. Your question will be answered within 30 seconds of listening. Virtually guaranteed.
so many good controllers are available - that can improve the sound.
I realize that belt compliance between drive and platter is an issue, however designers have long been aware. A good design is a good design, and compliance between drive and platter can be controlled.
If belt creep is as bad as others here have suggested, how can a simple change of controllers be heard as an improvement? Esp. considering one controller sounds better because it offers improved speed stability, yet both controlers must transfer energy through the exact same 'creepy' belt.
TBone
... while the SDS did wonders for my VPI TNT, it never got close to what I'm now hearing from a replinthed Lenco. And the SDS did nothing for the Lenco that I could detect.
If you had the flywheel with your TNT and replaced the rubber belt with a carpet thread, you would know with your ears that excessive compliance of the VPI rubber belt introduces speed instability.
Mine was an earlier TNT Mk II, sans flywheel. I had tried various belts including dental floss (never the carpet thread, though) without hearing anything special. The SDS made a MAJOR difference. And I tweaked the hell out of the table/arm/cart after finding that resonance damping and cones/points/dead balls affected the sound quality. Not to mention ICs.
And I should mention that my tubed phonostage, which started life as an NYAL Moscode SuperIt but would now be unrecognizable even by Harvey Rosenberg and George Kaye, is VERY revealing. So, all in all, I gave the TNT a pretty good shot.
But the Lenco demolished it, even with an SME III arm on it. With the JMW 10.5 (which was on the TNT), it's simply no contest. Whether all this is primarily related to speed stability or not, I don't really care :-)
You're obviously in Lenco heaven & unfortunately I have not heard a Lenco so I don't have that religion. But as you know from replinthing the Lenco, the original manufacturer's design may be just a starting point & perhaps some of the manufacturer's original design choices have more to do with ease-of-use, repeatability of results, and marketability, rather than absolute performance.
In the case of the TNT, the stretchy rubber belt around the platter must go. But it is not possible to get proper traction on a thread or dental floss without the increased surface area of the large-circumference pulley of the TNT flywheel, and also discarding the 3-pulley system that surrounds the platter. The TT also benefits from replacing the sprung suspension with a rigid mounting coupled to separate plinths for each suspension tower, motor, & flywheel. I used hard maple inside the stock elephant feet & a cut-up plinth top on a sandbox. Finally, for decoupling I elevated the sandbox on industrial springs. As a result of these changes (none of which are on the bona fide factory upgrade path) you would not recognize this TT as VPI "house sound." The total cost of all these mods was less than $200.
Having eliminated some of vagarities of the TNT design, I will eventually put a Teres Verus on this TT & see how much of a limiting factor the VPI motor really is. The Verus may just convince some people that it's simple & worthwhile to tamper with existing designs instead of throwing equipment up for sale on the Audiogon merry-go-round.
Anyone still using an out-the-box turntable simply hasn't lived :-)
On the other hand, rotating a series of $5K-$15K out-of-the-box TTs through one's listening room is really livin large.
The cutting lathe used to create the initial lacquer would have been designed to withstand the various amounts of drag imposed during the cutting process, but likely isn't perfect and some loss of speed at high modulated passages will creep in.
However, for most of us, we're not to the point where we can compare the speed stability of our "domestic" turntables to that of a direct drive monster Neuman or similar lacquer cutting lathe. It does seem likely that the best option would be to duplicate the properties of the cutting lathe in an audiophile's turntable. I don't think it would make sense to actually have a cutting lathe set up in the listening room.....or maybe it would.!!? Next thing you know well-heeled vinylphiles will be buying up old Neumans and mounting Schroeders to 'em.
-Steve
user510's system
Now, try not to give the uber rich any ideas there Steve... I got a line on a Presto cutting system that I am hoping to pick up for a song...
Mah heels 'aint so well...
--
Al G.
Perhaps you might have a career in digital data-packing schemes, where 'less' is viewed as progress.
In my view, this isn't your best shot at the Big Time in analog table design thinking.
This is a logical problem that falls under the Xeno's Paradox umbrella.
By infinitely splitting the difference between going there and getting there, you can generally prove that nothing ever gets there.
But that model doesn't describe the world as we know it.
No earthly system is perfect. But all serious systems intend to proceed toward perfection. That's going to include both mastering lathes, and also playback turntables. Given a perfectly mastered lp from a state of the art lathe, we're now at the point where solid progress on either of these systems would be perceived, merely, as progress.
J.
"If you're a horse, and someone gets on you, and falls off, and then gets right back on you, I think you should buck him off right away." Jack Handy
J.D.,
Nobody is making progress on cutting lathes that I'm aware of. If the progress of a TT surpasses that of a lathe you're going backwards. We must match the flaws of the lathe to get that much sought after perfect reproduction (or at least hear the speeed instabilities of the tape deck as OMalley noted!).
Unfortunately, no TT will ever match the flaws of ALL lathes, so we are stuck with imperfect sound forever. Maybe digital recording and playback IS the way to go :)
Automobile tires are often not perfect. But for car manufacturers to try and match the flaws of the tires would be ridiculous. Auto-makers, and tire-makers, realistically pursue optimal production side-by-side, not by tail-chasing defects.
You don't have to believe me, but you've got a logical fallacy going there.
All facets of the recording and playback system are focussed on achieving the best possible resolution under the circumstances at hand. That's the goal ::.. BEST possible.
Each aspect is always concerned with narrowing the difference between current state of the art and, yeah--- perfection.
Not with matching some imperfection somewhere else in the chain.
J.D.
btw.. there has been various kinds of progress re lathes and mastering procedures.... as an example, though not recent, I'd suggest Stan Ricker's Half-Speed Mastering --a major advance, if possibly too cost-heavy for everyday releases.
I have spent a great deal of time and energy on improving the short and long term speed stability of my Garrard 301 (which was already better than most belt drives) and have recently built a new TT which jumps a couple of notches further again.
When I reach the point of diminishing returns I'll stop. Until then, even allowing for the Beranek effect, I am convinced that improved stability is an unqualified bonus. I would go so far as to say that it's the sine qua non of great sound from a TT.
Mark Kelly
The better the speed stability the better the sound, the point of the turntable matching the speed instability of a lathe (which probably is minimal) would COMPOUND the fluctuation, not somehow balance it out.
.
Unless the motor and table where exactly the same, as well as the drag force of the cutter and sylus the speed in consistancies would occur at different times.
A slow-down on the cutter due to drag would sound "faster" played back with no error, on playback, stylus drag would sound "slower". At first this seems like it would cancel out, but on most tables the inertia would be diferent so it would not occur at the exact same point. Even worse if there is some sort of speed correction that would minutely increase the speed in response to sylus drag at the same time.
Picture the error amplitude as a wave, when two get stacked in the same direction the amplitude is increased.
Is that your point that if every thing was equal otherwise a slow down would become a speed up in playback? That would be really difficult to get right, but in theory you have a point. I think getting the amplitude of error as low as possible is the best we can do, and what most people rightly strive for.
Thanks for making me think about this instead of just making a statement,
-Erik
OK, we are on the same page. Initially I thought you meant that a slowdown of the lathe's platter would correspond to a "speed up" of the recorded sound when played back on a TT whose speed slowed down as the lathe did. Then I thought I might have been overlooking something.
To clear something up, I completely agree that matching the lathe's speed fluctuations is impossible. Unfortunately, it really is the only way to reproduce the frequencies and timing as they originally existed on the master before the lacquer was cut.
Thanks for your additional thoughts.
Mark,
I know it matters in general, but I'm talking about really refined TTs.
It sounds like you might be getting closer to a lathe in terms of speed stability. No way a stock 301 is near the speed stability of a cutting lathe, so I can see how you will improve sound by improving speed stability. I'm referring to improving on already refined TTs which are at or near lathe stability. If you can't speed up and slow down that platter during heavily modulated passages like the lathe's platter did, you will not reproduce the sound correctly.
I explained this more clearly in the Agon thread. Sorry for the "jumpy" writing style!
It is not a given that the lathe slows down under speed, I have seen no real evidence either way.
I think I have evidence that improving speed stability to well beyond the common levels is beneficial, which would tend towards negating the proposition that lathes slow under load as much as turntables do.
You are probably right in one thing - a Neumann VMS 70 would make a very nice turntable in my home. I even know where there is one in Melbourne (but it's being used).
Mark Kelly
.
Pat O'Malley
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so -Mark Twain
Yes it does matter. The cutting lathe has a vacuum hold down feature built in for platter stability. Also the cutting discs themselves are much heavier than a standard LP. I seem to recall they have a metal backing, but I can not vouch for that fact. Remember the cutting machines were designed with a lathe in mind: heavy cast iron foundations, and such. There may be some play in the drive system, as I am totally unfamiliar with what kind of system they utilize, but I would bet that it is not any belt drive.
Stu
Vacuum hold down has nothing to do with speed stability and neither does the weight of the lacquer (which is heavier than an LP). We're talking about platter speed stability here! What I'm saying is that, if cutting lathes are the end all in speed stability, then we already have the technology to produce the (relatively) most stable turntable. If they are not the end all in speed stability, then I pose the question. Are turntable designers wasting their time trying to produce TTs with killer speed stability? If the groove was cut at varying speeds it doesn't matter how stable your TT is. It won't reproduce the frequencies correctly.
Well, to my thinking and experience, movement of the disc, especially since force is being exerted upon it by the cutter of the lathe, must be an issue. I experience this on playback with felt TT mats and am a strong advocate of a clamping system.You certainly don't want any slippage of the lacquer as you are cutting it. I am assuming you have seen pictures of a cutting lathe. The cutter head has a heated blade and a vacuum attachment, but the lacquer itself does not seem to have a clamping mechanism. I wanted to rule out any speed variations of the lacquer/platter interface, and I, apparently, seemed to have glossed over that fact. My apologies.
Since some manufacturers employ DMM processing (Direct metal mastering) The cutting blade is actually cutting metal directly and there will be considerable resistance to the blade.
In doing a bit of research, I found this on the Neumann AM-32 lathe. The motor is a synchronous type with a "gear like armature about 10 inches in diameter, rotating inside a similar inside gear." The quotes are because I can't quite picture what they are describing. The wow and flutter is spec'd at +/- 0.035 % RMS. The platter weight is given at 65 pounds, and is coupled to the motor via an oil filled coupling to lower motor noise. This is from "the Handbook for Sound engineers": Glenn Ballou, ed. The oil coupling seems to be a sort of automatic transmission to me.
According to the Neumann article in Mix magazine, Neumann invented direct drive cutting lathes in 1931, so I guess the boom in DD TT's in the 70's came about from the Japanese manufacturers emulating the cutting lathedrive systems. It also means that their lathes had a pretty heavy duty motor if it was 10 inches in diameter. The torque produced by an armature of that size can be tremendous and the oil coupling would smooth out motor noises.
Most Scully lathes have a gear drive, and I would guess a hyploid drive would give the smoothest power transmission and speed stability, but I am totally unfamiliar with the underpinnings of a record lathe having only seen pictures and a description from the top exterior point of view. They did have a gear box from what I can research. Considering they were made in the 40's, I would guess that they use straight cut gears.
But since these common cutting lathes feature things like direct drive and gear drive, my guess that speed fluctuation would be minimal.
I believe, in playback, motor EMF field proximity to the magnetic cartridge, belts stretching while in play, suspension twisting, cartridge design probably all have greater effects on the sound than the original cutter lathe speed. Just consider how much laser cutting of styli have affected sonics, even on LP's pressed at the beginning of stereo. The issue has always been more on the playback side, rather than the manufacturing side.
Of course, YMMV.
Stu
Don't the later versions of the Neumann lathes use the Technics SP-02 DD motor? I use a SP-10MKII, and it is speed stable enough for my tastes.
the record lathe descriptions are high on the cutting head advancements and seem to ignore the platter motor and bearings. I believe I've read somewhere where Stan Ricker modified or replaced a motor with a Panasonic, but I can't find the article, so I can't vouch for the fact.
The lathes all have their motors mounted deep in the cabinets, at least judging from the photos, with a fairly long shaft to the platter. That ought to keep the EMF fields well away from the cutting heads.I know very little about these lathes, only from I can glean from various articles. Sure wish someone more knowledgeable could give us more information.
Stu
?
Pat O'Malley
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so -Mark Twain
because a brand spanking shiny new one.. if not an exact 'idler' but a rim drive ..which is newer and probably way better.
here's hoping they turn their heads.
Pat O'Malley
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so -Mark Twain
...that this new assembly can be used on most any platter, although he states quite clearly that the effect is much more significant on lower mass platters than higher mass platters. i believe i read that the effect was quite minimal (if any) on the highest mass platters out there.
Correct on both points. The Verus motor should work with any turntable so long as the motor can be placed adjacent to the platter. The benefits of the Verus motor compared to a Teres belt drive motor are more apparent with a lighter platter. However, even with a 70 pound platter a group of listeners still heard a notable improvement.
Hi Chris.
I've a question about this current Verus design:
I notice that it, like the previous rigid-belt drive implementation, essentially forms a solid coupling between the driven platter and the driving motor armature (rotor). As such isn't it likely that any 'significant' difference heard will be due to the inherent characteristics of the different motor rather than the method of drive? (belt versus tire)
Another Q:
Why didn't you go with a more traditional "idler transmission" drive train rather than the direct coupled design? It just seems that a transmission would offer some mechanical advantage for the motor and present a less "compliant" method of drive.
-Steve
user510's system
Steve, I can tell you that the differences between the Verus and Signature motors are mostly due to that motor itself and not the drive method. For some reason the "Direct Coupled" part of Verus seems to be almost completely overshadowing the more important motor topology. Good call...
We selected the Direct coupled approach for two reasons. The main reason is that we wanted the most intimate possible coupling of the platter and motor. The Verus motor is smooth and quiet enough that isolation is not beneficial. So any intermediate coupling just gets in the way. I would like to have used direct drive but there are a lot difficult and expensive mechanical problems with that approach. Also it completely precludes use with anything but a ground up direct drive design. An idler is a less intimate motor to platter coupling because there are two friction surfaces and double the compliance. The mechanical advantage from the idler is lost on the Verus motor because it has superb low speed characteristics. Higher RPM offers no advantage. The Verus motor is unique in this way.
The second reason is simplicity. An idler adds another wheel and bearing that must be well designed and implemented otherwise they will degrade performance. Direct coupling is as simple as it gets, but it only works with a motor that has excellent low speed characteristics. As Einstein aptly said "things should be as simple as possible, but no simpler".
it should be possible to implement this new motor as another rigid belt drive and achieve approximately the same sonic results?
-Steve
user510's system
There has been a long running thread over at A'gon/Analog forum on the topic.
I'm curious enough to have placed a request with Chris for a tryout on my own. I should get mine sometime mid Sept. Imagine a long waiting list of current Teres owners wanting to upgrade.
Consider this:
27 lb shot-loaded platter spinning on a beefy Teres bearing getting its drive via tire at the rim rather than belt.
The motor is something quite different from the previous Teres status-quo as well. A non-cogging AC synchronous with eddy current brake as damper and a separate power supply. Understand that the motor isn't off-the-shelf. Teres manufactures this item themselves! I'll forgive Chris for touting the "eddy brake" as an innovation. Every 301/401 and TD124 owner knows that "eddy current dampers" have been in use for quite some time.
Anyway I'm curious to see how the "Verus Upgrade" compares against my TD124. As it is now, the Teres that I have is very very good at delivering the goods in all but one critical area.....musical energy. It lacks that last bit of energy and explosive drive that a decent idler drive should produce. Perhaps this latest upgrade is the answer. Time will tell.
-Steve
PS: imagine a VPI Scout with a "direct coupled rim drive". I wonder what HW is working on these days?
user510's system
You would be surprised, then again maybe you wouldn't. Can't sit still too long in this business.
You should hear a Scout rim driven by a flywheel, amazing!!!!
You mean like an intermediate , or idler wheel drive, except with, presumably, an increased-mass intermediate wheel ?
J.
I think it's like they've been reading our mail. Well, not really. But consider ....
User 510 puts beltdriven Teres on the shelf after hearing classic Thorens rim drive.
J.D. won't shut up about the 'listen-thru' downside of idler versus the 'trashed timing' deal-breaker of beltdrive.
Mosin creates an Idler Drive table that makes great strides from the standard lenco renovation. With cosmetics to challenge the bigs ....
And most significantly ---
"Certus drive technology begins with a unique (patent pending) motor topology (permanent magnet, multi-phase synchronous)
with extraordinarily low torque ripple."
... Sounds more than a little like investigations already made and public from Mark Kelly.
J.
explains how his writings directly influenced Chris' thoughts on idler drive, and, thankfully, again reminds us of the debt we owe him for his revolutionary ideas on turntables in general, and idler drives in particular. And of course none of johnnantais overly-long missives would be complete without a reminder that there is no musical joy to be derived from any belt-drive tt, which are consistently 'trashed' by his own beautifully crafted Lencos.
I shall now take a moment to contemplate the genius that is.....johnnantais.
I don't want to rain on anyones parade but Johnnantais did not influence my thoughts about idler drive.
I have read some of his writings and have been amused about the imagined war between belt drivers and idlers. Actually I am just pissed off that nobody told me about it... No one even invited me to the battle.
of the Nantais Idlers' down the Main Street of Lenco Land.
In this far-from-unusual photo, johnnantais carefully explains to a woefully misinformed belt-driver that his equipment is shit, and he's a moron. Yes, there's trouble, and it starts with a 'T', and it ends with 'B', and that stands for Belt-Drive!
...... 'Spray'N'Wash', the Turntable. ......
Whilst thusly immersed, you can join all of us in rejoicing that his moment -- his Eureka, Big-Time, All-Or-Nothing Momemt -- is nigh.
Watch with sublime satisfaction as the Lenco L75 Intro article at Six Moons makes it's inexorable progress toward the light of day.
There is already material there to be joyous about, but soon -- Valhalla.
I can see the sharks being jumped, like never before, right now.
Hope they discuss the "Spin-Art" era.... My absolute fave.
Cowabunga. Surf's up.
!
the guy really does believe the world revolves around him..
The first 2 weeks of the "Despote" posts with him were enough with me.. I must have missed something .... why doesn't he post here anymore?
Have a great day!
Rick
May have something to do with the few rebellious peasants here who dare to call him on his arrogance and constant self-satisfaction over the Huge Changes he's brought to the world of audio. Not to mention that he's really boring. That's a bit different from the 'Despot' site where 99.999% of the posters are hero-worshipping johnnantais disciples, ready to drink the grape-flavored-but-a-little-coppery-tasting Grape Kool-Aid of their Exalted Master.
As an aside: there are people on this site who are, shall we say, determined in their beliefs in their own tt strategy. I have no problem with that, even when my own system is denigrated, because a) it's only stereo stuff b)none of them take on the mantel of Supreme Audio Adviser and c) who knows, I might accidentally learn something.
See this Clarisonus article from 2005. "Motors for Turntables - 1" J. Atwood. The article has a few parts and is worth the read if you haven't already. Link below:
I'll have to admit that I was really taken back at being "blown away" by my initial listen to the TD124 using a mediocre arm and the DL103-R cartridge. At that point I knew that the things that that this combo did well were the most important to me.
-Steve
user510's system
I think Chris was referring in that article to the use of an "eddy brake" with his Cetus Direct Drive TT as being the innovation of sorts.
Do you know if any of the Technics or any of the other older Direct Drive tables used an "eddy brake"?
Just curious.
Nobody here but us chickens.
_________________________
I do not believe the DD TT's used an eddy brake. They used a servo system to monitor motor speed, IIRC. The concepts involved here are very different.
Stu
I've got nothing on Technics. (Not that I wouldn't mind owning a nice sp10mk2)
I did read somewhere that "Eddy Brakes" have been in use on diesel-electric locomotives since their introduction way-back-when. In other words, that is how the locomotive stops the train, by an "eddy brake".
If I understand correctly The Verus direct coupled 'thingy' is an adaptation of the Certus direct-drive motor. Perhaps I should go back and re-read Chris's text.
-Steve
user510's system
A diesel/electric locomotive uses what is called a "dynamic brake" where the traction motors (the electric motors that directly drive the wheels) are re-wired through a series of relays and switches to work as generators with the main alternator of the locomotive providing the field current.
As the traction motors operating in braking mode create electricity it is sent to the dynamic braking grids (think super duty toaster wires) and converted to heat.
The system works really well on the newer locomotives, you can basically stop a train without using air actuated train brakes(the kind of brakes each car in the train is equipped with)!
--
Al G.
experience in the matter. I just didn't research the matter deep enough. I did come up with examples of eddy current brakes in use on rail cars however.
Here is one link to an example of an eddy brake being implemented on a rail car. Perhaps it isn't in wide usage yet, or if ever
user510's system
Which is a nice way of saying that everything to do with the braking systems in use today is 1940s technology, adapted from George Westinghouse's 1890s technology when it comes to air brakes.
None of the US railroads use anything as forward thinking as the eddy current braking system in the link provided. That system, I believe, is in use on the "bullet trains" of Japan. A Mag/Lev system would use a similar technology.
Fascinating technology but as long as our government is not interested in funding research for high speed passenger rail transport systems, that technology is a long ways off for the USA.
Sorry to mix politics into a perfectly rational discussion about magnetic propulsion! I was limiting my thinking to domestic rail!
I am rather interested in the Teres drive. It would simplify a project that I have been mulling over.
--
Al G.
I'm afraid my discussion about eddy current braking technology isn't going to go very deep. The example given in my previous link is a linear application. I do recall finding something somewhere about an application for a rotating disc that had eddy currents applied in such a way as to slow the rotating disc. Just like in the Garrard and Thorens examples but on a much higher scale of forces. Whatever.
re: NA railroad traditions. Yeah. They really are slow to adapt new technologies. And with a long tradition of same. Famous for it.
It brings to mind the lower Columbia River and the barge transports that operate between Portland and the Tri-Cities hauling grains and other agricultural products. It could have been the railroads getting that business, but for some reason they didn't seem interested. Hence the barge business.
Somebody different will have to come in and operate mag-lev transports. Perhaps an air-line company or similar once the public decides it wants it.
-Steve
user510's system
If they keep going they might arrive at a solution where they couple a high quality motor with advanced speed regulation directly to a high mass/well damped platter. Maybe it will be called something like direct drive?
Good lord what's next?
Ed
We don't shush around here!
Life is analog...digital is just samples thereof
The 'CERTUS' Direct Drive Turntable
just a tad...
Ed
We don't shush around here!
Life is analog...digital is just samples thereof
I'm not certain I even like this one enough todrop that kind of cash. Now if I could get a SP-10MKII with an EPA-100 in an original plinth...
We don't shush around here!
Life is analog...digital is just samples thereof
Ahhhh...now thats better.
We don't shush around here!
Life is analog...digital is just samples thereof
nt
nt
.
:-)
I understand the new Verus motors have started to ship. Has anyone heard them yet?
.
* clearer sounding
* slightly better resolution
* slightly better depth
* better separation of instruments
* more realistic tone, wider palette of tonal colors
* sounds more solid, can’t detect micro speed variations.
Loss of delicacy... which could really mean loss of tiny neurotic tentative speed changes being interpreted as delicacy.
Pat O'Malley
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so -Mark Twain
a linear, well-presented and articulate analysis.
But, jeezus, the motor/controller costs 1600.00 bucks. Could get a sweet, oh so sweet 301 for half that.
Thing is, if you've already got the Teres , and have done some serious build work on the chassis and the platform and all the rest ...
..to be able to turn it around (sorry) to idler status, well, 16oo doesn't seem that atrocious.*
What seems atrocious, though, is the visual design of the thing. It's almost a bit Dada ... a waggly tower thing with a spinning wheel on the top ? Erf.
Even the slightest Anti-Rube-Goldberg design help would have been welcome with that. (Encase the drive-wheel except for the business end ?
In a column that looks designed to stand next to the teres base ? A little bit ?) Again, erf.
Not sure, though, that you get a 'sweet' 301 for 16oo. You could definitely get an immaculate 401 --maybe unused untouched nos-- for that.
But in the grey-grease category of 301, you get a Really-Kicked-Around one for that.
Prices for a nice-condition grey-grease 301 are appallingly above that, and super-condition routinely brings circa-$3K at this point. Giant-sized ERF.
(( and, btw, aren't we seeing a lot of reason for the counterforce/smoother-outer of a grease bearing in this thread ))
J.
* guess it comes to your commitment to the teres schtick. I think this new 'belt-is-ng' stance is going to shake a few foundations...
Also-- I wonder if now the basics of the Teardrop design are sensible anymore, and whether this tower-with-a-wheel thing is only a sap to current ownership,
prior to bringing out a new flagship that actually accomodates and looks as though it had been designed for edge-drive.
(or Power Direct Drive. Or Magic Drive. Or whatever term they're avoiding "Idler" with.)
look. How about a base with interior, adjustable-tension springs, designed to move the motor pod and idler wheel to proper contact with the platter? Or something...?
I'm sure there were marketing um, issues , on how exactly to present this new gizmo to the Teres customers. My god, Doug Deacon alone has spent countless hours perfecting his 'belt' drive system-now, 1600.00 bucks later, all that's thrown out. Which takes us to.....
"...you get a 'sweet' 301 for 16oo."
Actually, I think prices are dropping a bit. I've recently seen several 301's go for under 700.00. Granted, these are the bottom-of-the-line white or cream oil bearings, but even counting the shipping from the U.K a diy'er could be into a-yes, I'll say it, "sweet", though admittedly low budget-301 tt for a thousand bucks.
I've seen two 401's recently go for under 5 bills.
"....your commitment to the teres schtick...."
As part of the preceding paragraph, if you could do a 301 deck for 1k, you've already saved 6 (or is it 7?) hundred by not buying the 'Verus'.
Re-selling your Teres tt provides more fabulous cost savings.
BTW, this is with All Due Respect to Chris Brady, who has always appeared to be a real gentleman, even when entering threads, such as this, that aren't entirely, or even necessarily, complimentary to his designs.
Let's hope they bite that hook.
But could this have a trickle down effect? Will Roy Hall be importing/exporting rim drives?
Pat O'Malley
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so -Mark Twain
"Magnetic Damping, Icing on the Cake"
"To further stabilize platter speed the Certus drive system employs a (patent pending) eddy current brake to provide magnetic damping. The eddy current brake applies an extremely uniform braking force. This uniform force is vastly greater than the highly variable force of stylus drag. By applying large and constant forces from the low cogging motor and the eddy current brake the proportional size of the force from stylus drag is dramatically reduced. "
Wow.
An " Eddy Current Brake " ????
Amazing. Check out their tech statement, at the link.
J.D.
What's next, mushrooms and dustbugs ?
nt
The Thorens TD 124 has an eddy brake and I believe that Teres is merely taking a page from Thorens' rim drive TT's. I don't see how they can get a patent on a widely distributed design, unless their brake design is different in application or construction.
Part of the issue is that a conventional belt drive has a tendency to build up momentum and it will reach a point where the momentum will exceed the desired speed. Most motor controllers reduce this effect by reducing voltage so that the motor is just barely pulling the platter assembly, and thus there is always a bit of drag for the motor to work upon. Here the sheer mass of the platter acts as a brake.
If your TT has speed adjustments, you can hear the effect by using a bit of grease instead of oil in the main bearing. The grease will do several things. It will 'tighten' up bearing clearance. Secondly, it will add a bit of drag, necessitating an adjustment to speed up the motor. In essence, you will be duplicating what the Teres motor is trying to accomplish.
I do this with a VPI TT with SDS and it works quite well with a noticeable increase in information retrieval.
Stu
> > If your TT has speed adjustments, you can hear the effect by using a bit of grease instead of oil in the main bearing. < <
Your correct, I have long used a special mix of viscous oils in my bearing to do three things:
1) limit bearing noise.
2) introduce a controlled amount of viscous drag.
3) couple the bearing/platter/suspension.
IME - with a DC motor/controller/heavy platter/suspension - viscous drag at the bearing level is preferred.
However, i do not recommend grease. I also don't recommend detergent based oils or sulfar based oils.
If you want to add viscosity and drag, simply use a heavy thicker oil such as gear oils.
TB1
The platter doesn't "build up momentum until it exceeds the desired speed".
A belt drive must actually be designed to run the motor at too high a speed to take account of losses due to belt creep (the elastic transfer of force means that the belt speed is always a fraction less than the pulley speed). Since belt creep is torque dependent, if the torque diminishes the platter speeds up. The important effect of Chris's design is that it eliminates belt creep. This cannot be replicated with any belt drive.
As Chris notes there is always some frictional drag but it is important to realise that ordinary frictional drag is not viscous drag eg it is not speed dependent. Grease does add viscous drag.
Mark Kelly
Well, IMHE, speed does make a difference if simply because the viscosity of oils and grease change a bit as the bearing heats up. Of course it does stabilize once temperatures stabilize, so I'll have to give in to your point.
In an older issue of Sound Practices, there was an interesting article by the designer of the Platine Verdier. Sorry I forgot his name, but he pointed out the fact that the audiophile practice of spinning the platter to determine bearing tolerance was not necessarily a good one. Having a slightly stronger motor with a bit of additional drag, as Chris points out, will swamp out some of the tendency for the belt to stretch, in the sense that you are already running the belt at the limits of its elasticity (well, I am exaggerating a bit, but I'm sure you understand).
It is not the solution that Chris has come up with, but it does work.
Stu
> > Having a slightly stronger motor with a bit of additional drag, as Chris points out, will swamp out some of the tendency for the belt to stretch, in the sense that you are already running the belt at the limits of its elasticity (well, I am exaggerating a bit, but I'm sure you understand). < <
Like everything,, a balancing act is required. A stronger motor and additional torque may cause additional noise/vibration. IME - thats never a good thing with turntables.
I have played with a variety of belts. I can tell you that in my experience, the best belt was neither the stiffest nor did it run close to its stretch limit.
As I have stated in the past, if your worried about the amount of speed instability inherited within a particular TT, simply compare it to a very good digital front end.
TB1
The article was by JC Verdier in SP #11 and was partially in response to a ridiculous piece by Gotz Willimzig in (I think) SP#10. I agree that J.C. Verdier's article is very good, he has some very interesting ideas on TT design.
In an odd way I have Willimzig to thank for my interest in DC motors - his article was such crap that I ended up doing a whole bunch of research simply to prove him wrong.
Mark Kelly
> > A belt drive must actually be designed to run the motor at too high a speed to take account of losses due to belt creep < <
In my current rig, my DC based engine runs at a slower speed, with enough torque to turn a heavy platter and a viscous oil (highish viscous drag) bearing. I ran it with three sizes of pulley, and the slowest speed easily sounded best, esp in terms of limiting noise & speed instability.
Stylus drag & Belt creep is a factor, but its no secret that it can be minimized with good design. Belt drives offer other advantages, notably low noise floor characteristics.
I realize that limiting compliance between the drive and the platter is beneficial to speed stability - but it needs to be done without adding noise. With the best belts and a super low noise floor system, you can hear levels of depth and detail at the very lowest recorded levels - offering superb dynamic capability.
OK, if your worried about a belts speed instability - it's an easy measure. Simply listen to the same song on a superb digital front-end and compare ... your ears will tell you exactly how much "belt creep" plagues the sound of your system - if any.
TB1
Huh? You deliberately run the motor too slow? Or did you not understand my post?
Belt creep cannot be "minimised with good design", the belt must creep to transmit torque. Belt creep depends entirely on the stiffness of the belt and the diameter of the drive pulley.
Mark Kelly
> > Huh? You deliberately run the motor too slow? Or did you not understand my post? < <
Well .... ummmmmm ... not "too" slow.
Maybe YOU didn't understand my post.
> > Belt creep cannot be "minimised with good design", the belt must creep to transmit torque. < <
Such a blanket theory/statement. Yet my practical experiences indicate that we have a very different understanding of overall turntable design, esp. as it applies to that big/bad variable known to many as the toxic analog avenger, or ... "belt creep".
> > Belt creep depends entirely on the stiffness of the belt and the diameter of the drive pulley < <
And you believe these are the ONLY variables, of which no valid solutions are warranted thru better design?
Actually, no need to answer, we are very polarized on this topic, and probably have very different expectations on overall system requirements. As John, Paul, George and Ringo once suggested, maybe we should simply 'let it be'.
TB1
Sorry if I was rude.
I don't know about the polarisation, I think we may be using the term belt creep to mean different things. I think you mean what I call belt slip.
There is a definition and physical analysis of belt creep (as I mean it) which shows that the only factors are the belt stiffness and the pulley diameter in a paper by Leamy "Analysis of Belt Drive Mechanics Using a Creep Rate Dependent Friction Law" which used to be here:
http://www.umeme.maine.edu/mjleamy/research/Papers/mjleamy_JAM_2002.pdf
But I cannot access it at the moment. If you are really interested I'll send you a copy.
Mark Kelly
Hi Mark,
All is good, I find this a fasinating debate / discussion, along the lines of DC vs AC motors.
Thanks for the link, I will read it tonight.
Mark, you have obviously done your homework and it is obvious you have a passion for analog / audio. That's why in essence, we are probably arguing the same argument. That said, I think we have different values, and perhaps different expectations.
No, belt creep to me is not slippage, it's defined by compliance in comparison to the motor / platter movement. In other words, the motors relative movement, its intended rotation of the platter, is influenced by unrelated complaince (belt).
It is a realistic issue, and perhaps a solid justification for why many audiophiles today prefer rim and direct drive turntables.
Although I respect that preference, I don't believe it's the only issue, and I certainly think it can be minimized - because I have proven so within my own system.
I'm firmly within the belt camp because of a variety of issues, notably I'm referring back to my expectations: ie superb low noise floor characteristics / large dynamic envelopes.
Compliance may effect speed stability, to one degree or another, that's a given. However with a good design, it allows for a degree of isolation from what I consider to be the MAIN cuplrit regarding vinyl replay: the motors inherited noise being "directly" transmited to the stylus.
TBone
"The Thorens TD 124 has an eddy brake and I believe that Teres is merely taking a page from Thorens' rim drive TT's."
You are correct using an eddy current brake is not new, but the implementation is new and different.
"Here the sheer mass of the platter acts as a brake."
Well not quite. The platter's mass will resist speed change, but it is not the same as a brake. The mass of the platter has a beneficial effect but is unrelated the application of torque and braking. Once the platter is up to speed two opposing but equal forces are being applied, friction or drag from the bearing and torque from the motor. As the drag increases the torque from the motor must be correspondingly increased otherwise the speed would not be sustained. All bearings have some amount of drag. As you have discovered increased drag is often beneficial. Drag is good only when it is very uniform. Drag from and eddy current brake is ideal because it does not suffer from turbulence as does a fluid (oil or grease). You are correct that bearing grease and the eddy current brake accomplish the same thing. However, the eddy current brake is more uniform and in the case of the Certus motor, the amount of drag applied is vastly larger.
The bit about turbulence is incorrect. The lubricant will be undergoing laminar flow because the tight clearance and low relative speed mean that the lubricant is way, way below its Reynolds number.
Mark Kelly
Claiming that by adding a lot of constant drag force, adding a little more doesn't make any difference is strange reasoning. What counts is how much that extra drag force is compared to the driving force or torque available to overcome it. They use up a lot of the original torque working against the constant drag force they introduce. If they didn't have that drag force, the affect of the drag force of the stylus would be be vastly less important. If somehow the effect of the brake is to increase the effective inertial mass of the platter, then it could be a benefit, but that's not what they say. This could be achieved in some sense if the breaking scheme somehow resists all changes in speed, both increases and decreases. Am I missing something?
Joe
Chris's explanation glosses over the real issue here.
Synchronous motors suffer from an effect which we could call "torque bounce" or "torque spring effect". This occurs because the motor is run with enough voltage to keep it above its drop out torque and the extra voltage reduces the angle between the rotor field and the stator. Any extra torque will cause the angle to increase, as the motor takes up the load and then decrease again if the load is removed. Any change in torque requirement thus causes the rotor to "bounce" back and forth. This motion is normally almost completely undamped as there are no viscous losses anywhere in the system.
The point of the eddy current brake is to supply the required viscous loss to damp the torque spring. It must also slow the response of the rotor / platter to a step change in torque requirement. This would be so small it would be unlikely to be significant.
Mark Kelly
"Claiming that by adding a lot of constant drag force, adding a little more doesn't make any difference is strange reasoning."
Let me clarify. For the sake of discussion lets say that stylus drag exerts 1 unit of drag and that the bearing exerts 99 units. That would require that the motor deliver 100 units of torque to keep the speed constant. If the stylus drag changes by one unit then the speed would change 1%. Now if we add 900 units of drag from an eddy current brake the total drag and torque is 1000 units. The same 1 unit variation in stylus drag will now cause only a 0.1% variation. So it still the same amount of drag but effect is divided by a factor of 10. Yes, the numbers are exaggerated and the case is oversimplified but it hopefully illustrates the principle.
Suppose a stylus exerts +/- 0.1g of drag force. The important thing is whether this change in drag force will change speed. It doesn't matter what it's added to, even 10 kg of drag force. The other drag force is constant. All that counts is the amount of variable drag force compared to the force moving the table. One competes with the other. You can't win by simply adding more drag force. In fact, you lose, because you drag down the driving motor. It's like trying to beat flexure by adding weights to pre-bend a beam. The weight of the beam still does its thing.
Joe
Joe, I am not following you. You are correct that in order for my example to work the motor must have additional reserves of torque. The Certus motor is capable of delivering enormous amounts of torque so this is a non-issue. At a microscopic level stylus drag variation will always affect speed. But the goal is to diminish the affect since it cannot be eliminated.
Using your example we are not trying to beat beam flexure, but rather trying to keep the flexure constant. The beam analogy does not quite fit here. But it could be thought of as a stretched string. The motor and the brake are on opposite ends of the string pulling it taut. And stylus drag is like a bird landing on the string. The bird will always deflect the string, but higher tension on the string will reduce the deflection. Does this make more sense?
Regardless of the theories (that often end up being wrong even when they seem solid) the addition of a substantial eddy current brake simply sounds better. I may be in the weeds with the theory, but our ears tend to tell the truth.
...how my Rockport Sirius III works in this area?
reading about your approach on this issue makes me wonder how it compares. i remember spending time in your room at RMAF and how much i enjoyed the Certus.
my understanding is that the Rockport uses an 'eddy current' motor with direct drive with an air bearing, 55 pound platter, and a servo which samples the speed 10,000,000 times a second which is 'said' to eliminate groove modulation.
it is at speed within three revolutions and stops completely within 1/2 revolution.
my ears tell me that is that it has a solidity and tonal correctness not otherwise heard.
mikel
Well, all turntables have measurable wow & flutter. What are the specs on yours? Furthermore, all analog tape recorders have measurable wow & flutter and so do cutting lathes.
With regard to the digital recordings that I made from your turntable, they sound just fine. However, they don't necessarily sound any better than similar recordings made from my belt-drive turntable.
Therefore, I think speed stability is a bit overrated. The reason is because if speed stability is so overwhelmingly important, then digital should sound absolutely spectacular to all speed stability enthusiasts. However, I don't think this is the case.
Another reason I think that speed stability is overrated is because multiple re-recordings on analog tape machines for mastering purposes in conjunction with cutting lathe wow & flutter sometimes produces excessive wow & flutter in the final stamped vinyl products. This doesn't include the effect of off-center spindle holes, yet none of these problems can be corrected by the most perfectly speed-stable turntable in the world.
In my opinion, speed stability is important, but analog in general, and vinyl specifically, produce speed stability issues that no turntable can correct. If you want audibly perfect speed stability, you need to go digital from beginning to end.
Best regards,
John Elison
"With regard to the digital recordings that I made from your turntable"
What turntable might you be referring to? Have you had access to a non-belt drive Teres?
"If you want audibly perfect speed stability, you need to go digital from beginning to end."
What about digital jitter? Jitter is a well documented problem that degrades the sound of digital recordings. It is a distortion in the time domain and remarkably small amounts of jitter are easily heard.
Analog is no different. Small errors in the time domain are easily heard. Wow & flutter measurements are coarse errors that are low in frequency and generally do not correlate well sound quality. It's like harmonic distortion. Easy to measure but not useful. Very small time distortions similar to digital jitter exist in analog and have the same sort of effect on sound. Many do not recognize it as such.
All sound recording techniques share the challenge of accurate reconstruction in the time domain. It's naive to say that digital is somehow immune.
> What turntable might you be referring to?
I made some digital recordings from Mike Lavigne's Rockport Sirius III.
> Have you had access to a non-belt drive Teres?
No!
> What about digital jitter?
Jitter has nothing to do with turntable speed stability. Furthermore, the audible effects of jitter in CD players has basically been eliminated years ago. The jitter specification on my 12-year old CD Transport via its I 2 S buss output is 5-picoseconds.
> Very small time distortions similar to digital jitter exist in analog and
> have the same sort of effect on sound. Many do not recognize it as such.
I don't believe "very small time distortions similar to digital jitter" exist in turntables with 27-lb platters. Sorry! I don't buy it!
> All sound recording techniques share the challenge of accurate reconstruction
> in the time domain. It's naive to say that digital is somehow immune.
Digital does not have measurable wow & flutter and jitter is a non-player in this discussion. Sorry!
The point I'm making is that there is so much wow & flutter already recorded into LPs that the effect of a turntable with perfect speed stability is insignificant compared to a turntable with reasonable speed stability.
Best regards,
John Elison
The audible improvements I've heard through three generations of clocks in my CDP down to the latest Superclock 4, argues that there is still progress to be made in eliminating digital jitter. With each successive clock the unit sounds more like an analog front end. I therefore suspect that digital jitter in a CDP is a bigger problem for the ear than speed stability in a high-quality TT.
Actually, I don't think either one is a problem. If you want a CD to sound like an LP you simply take a CD recorder and copy an LP. I do it all the time.
BTW, what is the jitter measurement on your best clock?
Best regards,
John Elison
Unfortunately Audiocom doesn't publish jitter data. In any event, jitter in a transport or player is a product of other circuitry in the digital section as well. However, the SCD-1 had pretty low jitter figures even in stock form, so the improvement one hears with aftermarket clocks is happening at low thresholds of jitter. If you don't believe there has been meaningful recent progress in clocks (such as the external clock option available in Esoteric's premier 3-box solution), then I'm certainly not about to convince you.
Are you implying that your CD recordings are indistinguishable from LPs played on top-quality TTs? If so, then perhaps I should trade in my $10K battery-powered SCD-1 with Silver Rock transformer analog stage for your 12 year old transport.
> Are you implying that your CD recordings are indistinguishable from LPs played on top-quality TTs?
Well, they sound pretty close. Check out the following:
The Challenge!
per Challenge terms---$250 to the audioasylum done
So how many times out of five did Lavigne fail to detect the difference?
The shootout results are indeed surprising if you're burning CDRs that are being played back with standard RBCD sampling. Your results would be less surprising if you recorded and played back hi-rez. In recent TAS, Bob Ludwig reports that his 96kHz/24-bit masters contain over an octave more HF when pressed to vinyl as compared to transfer to RBCD. As to degredation contributed by clock jitter, Robert Harley reports hearing an improvement moving through three successive clock sources for an Esoteric X-03 with accuracies of 3 parts per million, 1 part per million, down to .05 parts per billion. It's particularly interesting that vanishingly low jitter in a digital playback system improves the listening experience even for CDs that were recorded with more compromised jitter control. Perhaps there are analogies to be drawn regarding the quest for the grail of speed stability in analog front ends...
Admittedly there is more to a player than its clock, but all other things being equal, it's remarkable that the ear can detect such small errors in timing. Whether your ear is trained to hear the difference or whether you care about the difference is a separate matter.
Mike failed to detect one out of six trials. It was number 3, I believe.
The test was stacked in his favor because he picked all the pieces and he was intimately familiar with all the pieces as well as being intimately familiar with his mega-buck audio system.
The test was conducted using a Redbook CD-R played back on my 1995 Audio Alchemy CD player connected with Monster Cable interconnects. I also used Monster Cable interconnects to connect my Alesis Masterlink CD recorder.
There seemed to be a slight sonic difference between my CD-R and the real thing from his Rockport Sirius III, but it was pretty close. In fact, two others attempted the blind test after Mike and they failed every trial. Of course, this proves there was an audible difference, but I found it interesting that the others thought my CD-R sounded more like vinyl than vinyl itself.
Best regards,
John Elison
That's certainly food for thought. I've kept AA DDSII and PS Audio Lambda II transports for comparison to the SCD-1 I've been modifying over the years. The SCD-1 transport section is more resolving & dynamic, but the AA is notable for smoothness and continuousness similar to vinyl. Perhaps the human ear in series with the loudspeaker adds the most jitter or worse kinds of instability.
I remember in the 90s putting up to two AA dejitter boxes in series between the Lambda II and a Theta Pro Gen Va. For whatever reason the AA boxes added hash to the sound. Perhaps if I'd used the then new I2S interface things would have improved.
Regards,
Dave
"the audible effects of jitter in CD players has basically been eliminated years ago"
Eliminated??? I would not call 5ps eliminated. Yes great progress has been made to reduce jitter but it is still there and it still affects sound. Sounds like the perfect sound forever mantra all over again...
"I don't believe very small time distortions similar to digital jitter exist in turntables with 27-lb platters"
Fair enough, but I do. I have done plenty of experimentation that clearly indicates that jitter like distortions do exist and when properly dealt with the sound is correspondingly better. I will admit that I could be wrong about the particulars about my "belief" but I have no doubt that there is something going on with vinyl that behaves like jitter. So do you have any experience or even measurements to back up your belief?
"The point I'm making is that there is so much wow & flutter already recorded into LPs that the effect of a turntable with perfect speed stability is insignificant compared to a turntable with reasonable speed stability."
Your point is logical and even sounds reasonable. But the truth is that improving speed stability does make for better sound. Maybe if we were closer to perfect speed stability then it would not make a difference.
I've heard a Rockport Sirius III and in my opinion it sounds no better than my Sota Millennia Vacuum.
'Nuff Said.
John Elison
"The point I'm making is that there is so much wow & flutter already recorded into LPs that the effect of a turntable with perfect speed stability is insignificant compared to a turntable with reasonable speed stability."
'Nuff Said.
The speed stability of the Rockport is entirely down to the accuracy of the servo loop. I struggle to understand how any servo loop can possibly achieve the stated levels of performance but that probably just says that they know more about it than I do.
Mark Kelly
Eddy current brake advantages include :* Adjustability of damping system.
You can't change the 'effective inertial mass' of the platter -- especially not on-the-fly, but you can-- in effect--- adjust the top end of that inertial mass via the eddy-brake. (Though obviously doesn't increase flywheel effect).* Motor drive runs at mid-capacity.
With the eddy-brake engaged somewhere between full and off, the motor is only being compelled to run somewhere in the mid-range of it's capacity. Not at the extremes (assuming max capacity would be with brake full-on).* Pitch control.
Eddy-current brake allows adjustability of platter speed, magnetically, smoothly and without physical or electrical connection to the motor, further allowing full-current and full-torque operation of motor.Sorry if this isn't a real physics-class explanation. I may even have some aspect slightly off... But it is the general gist of the Eddy Brake.
Others will be able to supply the physics part of things if needed.J.
Sorry J.D. but your physics is a bit off here.
First, an eddy brake does not add inertia to the system, it increases the system's viscous loss. In a linear analogy the first is like increasing the mass of you car, the second is like increasing the wind resistance. The mass will slow you down when going uphill but speed you up when going downhill, the increased resistance will always slow you down but be more effective the faster you are going*
Your second point is reasonable but I don't see that it makes much difference.
Your third point is not correct, the eddy brake does not affect the speed because the motor is synchronous.
*Actually there's a gloss here, aerodynamic resistance is proportional to the square of the velocity where viscous loss is proportional to velocity. I just couldn't think of a linear analogy that didn't complicate the argument.
Mark Kelly
I did say that it "..obviously doesn't increase flywheel effect.." and maybe I should have reiterated that it wouldn't add inertia -- but I did mean that.
I did say "You can't change the 'effective inertial mass' of the platter".As regards the brake "not affecting the speed because the motor is synchronous" ..
...well, original poster Jsm wasn't specifying, either, as far as I could tell, other than saying, as he does, "the driving force".
My mistake would be thinking of the Induction motor as the drive force, as in the Garrard. Wherein the brake does in fact adjust speed.(( And --now that I think of it ---maybe this is the source of the lack of agreement here, with many considering the standard implementation of eddy-current brakes (garrards & thorens, others) as the "drive force" .... And others presuming ac synchro, as in the teres drive. ))
Also, I'd hazard to say, there's a difference between what would ever be considered allowable in a physics textbook, and what stands in for that, at least as regards the rest of the non-physics speaking universe.
If I say, for example, that .... :
"an eddy-current brake is like sticking your finger on the platter wall as you play a record. Its going to slow down, for sure, but in spite of that, it's going to smooth out."... well ... it might not scan or parse properly for a physics analysis, I don't know. But it has the distinct advantage, nonetheless, of being ... well, true .
J.D.
Your second two points have nothing to do with variable stylus drag. It is beyond me how simply adding a drag force to a table damps it unless, as I said in my first post, it goes both ways. The force decreases when the table slows down and increases when the table speeds up. That would have the desired affect, but the Teres write-up didn't describe its actions in terms of a variable drag force. The whole thing is silly anyway, if one considers the driving forces and stylus drag forces of well-designed TTs. Many other things will have a much bigger effect on TT speed that the stylus drag variability.
Joe
Damping that is not physically or electrically making connection to the motor drive --- as with the eddy current brake--- certainly reduces or smooths out the Cogging side effects of the motor.
It would appear to have a beneficial aspect re Stylus Drag --(which after all, like cogging, is a temporary but noticeable detriment to speed stability)--- but I'll let you & CB wrangle out the math on that one since it's not my category.
J.D.
Also, If the speed stability is "quantum leaps" ahead of what they had, does that means that the stability was previously very poor?
I guess technically a *quantum leap* could be a very tiny increment, after all quantum leap implies only that there are no intermediate states, it doesn't really say anything about the magnitude between the states.
Kinda makes it a ideal marketing term when ya think about it that way!
:)
No Guru, No Method, No Teacher
good one,
Stu
"Also, If the speed stability is "quantum leaps" ahead of what they had, does that means that the stability was previously very poor?"
Best line I've read all day. You deserve a prize for it.
Well, you get the idea. :-)
Nobody here but us chickens.
_________________________
.
No Guru, No Method, No Teacher
nt
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