It's not a new idea. The Garrard 301 used an "eddy current brake" in much the same way. The degree of braking was used to fine adjust speed, but it also stabilized the speed. Don't know of any other "modern" turntables that do this, though. |
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Basis, Galibier are two that I've noticed having a bearing with more drag than one might otherwise expect. I expect there are others but these I have first hand experience with. If you spin these bearings with no platter they don't turn very many times. Add the platter and they spin a few more times before stopping. I would also think in the case of these two bearings that it is the tight tolerances and oil viscosity that provide this resistance.
I think of this as being a bit different than eddy current breaking, but it is hard to consider the bearing a table uses without also considering how the platter is driven. (BTW, in addition to Mosin, I understand Teres is using eddy current breaking in their DD tables and maybe in the Verus drive. But I'm not sure about the Verus.) As one can imagine, motors with differing degrees of torque may work better with a bearing with a bit more or less drag. It gets even more interesting when different belt materials are added to the system.
In contrast I recall stories about Walker tables and how they will spin a long, long time on that magnetic field bearing. I don't know what Walker uses for a motor, but I would expect that it is a very low torque motor.
The point I'm trying to make is that you have to take the drive system on any table as a whole. There are many designs possible to get to a solution. |
Basis, Galibier, Teres, Redpoint, Mosin's Saskia, Garrard, probably many others. Chris Brady wrote an effective explanation of how a carefully chosen amount of steady-state drag (from the bearing, an eddy current brake or otherwise) can minimize the effect of variable drag events (i.e., stylus drag). Check the Teres website, it's on there somewhere. The concept is that if the motor is working against a high steady load, the proportional value of any stylus drag event is reduced. That makes it easier for the motor/coupling system to overcome. If a table shows the motor/coupling system little or no load, each stylus drag event is proportionately much greater and therefore more likely to be audible.
Having heard most of the tables mentioned above, my ears agree that the theory has merit, always depending on execution of course - as Dan said. It certainly works with Mosin's table, brilliantly.
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Hey Doug,
Call me Win. I'm trying to outlive the "mosin" moniker, but without much luck. ;)
Anyway, Chris did give a great explanation, and there are various implementations of it. Even sheer mass at the platter can help when the bearing arrangement is designed with braking in mind, but there are other implementations. Properly used, the motor itself can go a long way to controlling the spin. Also, Garrard (as you already know) used a grease bearing very effectively as a dynamic brake. The list goes on, but the most important thing is to make sure the turntable has no runaway effect, or that it is not bogged down anytime during its operation. Free spin equals loss of control, in my opinion.
Best,
Win |
So I see that there are a number of tables that exploit this design principle in one way or another. Can anyone comment on the issue of bearing noise? Also, most of these tables are large and heavy. I'm using a wall mount shelf and therefore require a table that doesn't weigh a ton. Any suggestions as to models I should explore? |
Free spin equals loss of control, in my opinion.
That's the best way to sum it up! Dodgealum, there is no noise issue. Because a bearing is designed with some drag does not mean that it is being created by allowing things to rub together. For the 'table designer this is much like matching a load with an amp. The motor will be able to control things much better if it is doing work against the load. This is what the bearing drag is for. |
From a physics perspective, using the bearing drag to introduce a well defined load for the motor is certainly “sound” as nicely explained by Dougdeacon and others above.
The DPS differs from some of the other tables mentioned above: the bearing friction is significantly higher than on the other implementations since the DPS uses a light platter and doesn't have the benefit of the inertia of some of the above heavy mass tables. The reason behind the high friction is that, in comparison, any friction introduced by the needle (needle drag) is neglible. From my own experience, the DPS is one of the few tables with a light platter that does have any of the associated speed variations and in many ways sounds like a high mass design (of course the base is fairly high-mass anyway as it contains two layers of lead).
I have not noticed any detrimental effects for the DPS, especially not added noise. Several friends have commented that the DPS is in fact easily one of the quietest tables in our group with the blackest background (comparing to TW Raven AC, Platine Verdier, VPI Scoutmaster, Michell Gyro, etc.).
The DPS is IMO one of the most well designed and thought out tables out there. Everything is extremely carefully matched and optimized; e.g. Willi tried several different platter thickness and weight to optimally match the “loading” of the motor. If you are looking for a table with a slightly more compact form factor the DPS should be on your list. On the downside the design is not for someone who likes tweaking - the top base has to be replaced for a tonearm and it already comes with all the isolation and platforms you may ever need. |
I don't know of any direct-drive tables that deliberately use this strategy, except possibly in their electronics. Can anyone think of any? |
Lew,
Yes, there are direct drives that do it, although it may be a happy accident for some. By centering mass in the platter, some direct drives avoid excessive noise from their motors. As a result, they also introduce a better way to handle inertia. By my way of thinking, using inertia properly is key to the conversation, so in that sense, a lot of direct drives succeed. |
Come to think of it, Win, I see your point. I observed the herky jerky movement of my SP10 motor without the platter. It almost threw itself off the benchtop where it was sitting. So clearly, the mass of the platter smoothes out the operation. Further, the mass of the platter is constrained to within certain limits, if a servo dd table is to operate well. Of course, that is quite different from an eddy current brake, but the principle is perhaps similar. I just had not thought of it that way. |
Lew,
Chris Brady's Certus DD designs are said to implement this principle very thoroughly, as does his Verus rim drive, both due to the the motor design.
His belt drives used bearing design and choice of lubrication to achieve a similar effect (as do the similar designs from Galibier and Redpoint). Bearing noise on any of these is nonexistent in any system I've heard, including mine. Motor noise transmitted through the belt, while very low, is more audible than that.
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The only turntable so far which did it right (i.e. - correct application of "friction" to stabilize movement AND to provide additional damping to the platter) is/was the old venerable Platine Verdier in its original form (pre-1992) of bearing (without the ball support). Its a true eddy-current brake applied on a large diameter and fairly strong. The large diameter provides excellent damping on the turntable platter itself (which however was only a side-effect of the vertical bearing being suspended by magnetic force). Somehow archaic in execution, but very effective indeed. |
Dertonarm,
the only table? Really? Perhaps you should try to listen to more 'tables. ;-) |
This is an interesting discussion, thanks to all. It seems to be the case that some other manufacturers take a quite different approach. Nottingham, for example utilizes an extremely low torque motor, so any kind of breaking is out of the question.
I have no idea myself what are the merits of any particular design choice. All I can say is that I have, and like, my Basis Debut table and I have, and liked some of the others mentioned. |
On a related point, one thing I've been wondering is why not integrate a flywheel with the motor pulley. For AC motors in particular this would have the advantage of smoothing out cog noise at the motor source, rather than pass it on to the platter(or an outboard flywheel) through the drive system. I know some of the older heavy-duty high-speed motors have some built in flywheel effect; it's surprising that this approach is not taken with some of the smaller motors in current vogue. |
A flywheel can very well create problems if not done the right way.
It is only suitable to motors featuring a solid axis shaft and a very good and rigid bearing. The flywheel - if done the right way - add considerable amont of inertia to the motor shaft and to the whole moving system. Therefor it requires solid construction. Especially if the flywheel is directly attached to the pulley or part of it (which is the only way to use the inertia moment of the flywheel to smooth out most imperfections of the motor itself). The smaller motors envogue right now do not fare very well with flywheels.
The small motors common today have 3 big advantages. Even if all turntable-manufacturers using them do list some other advantages, it all comes down to these 3 only....:
1. they are inexpensive.
2. they are inexpensive.
3. they are inexpensive............ |
Dgarretson,
I addition to the practical difficulties that Dertonarm pointed out there are some good theoretical reasons against using a flywheel at the motor. In all motors motion is produced by magnetic attraction. When there is no drag the
magnetic fields in the stator and rotor will be perfectly aligned. When drag is applied the magnetic fields pull apart and the attraction creates torque. This is a very desirable characteristic in that torque is almost instantly created in response to a load perturbation. I say almost instantly because the rotational inertia in a motor delays the delivery of torque. Any delay in torque delivery adversely affects the motors ability maintain constant speed because the corrective torque is being applied after the fact. The longer the delay the worse the problem becomes.
Belts, particularly stretchy ones, have the same effect. They filter cogging, but also delay delivery of torque. Filtering cogging is a good thing, but it comes at a price. In many cases the fix is worse than the problem. Much better to just start out with a motor that has low cogging.
In addition to the theoretical arguments there is plenty of empirical data that indicates that low inertia motors tend to sound better. That has been my experience.
BTW: Certus turntables use an eddy current brake. The braking force is much greater than what a belt drive mechanism can keep up with.
Chris |
Hi Dan_ed, I do not use the Platine Verdier. Furthermore I do not see that I have refered in any way to the sound of the Platine Verdier.
Did I ?
My comment was about a construction feature of the Platine Verdier which was used in this turntable indeed for the very first time in this particular context.
BTW - I have listened to about every commercial turntable released on the market the past 32 years (and a few non-commercial TTs too...).
However - you would never read any comment from me regarding sonics about any current market product ever. |
Ok, Dertonarm. I'm just wondering what you meant when you posted this. The only turntable so far which did it right (i.e. - correct application of "friction" to stabilize movement AND to provide additional damping to the platter) is/was the old venerable Platine Verdier in its original form (pre-1992) of bearing (without the ball support). Nobody else has gotten it right? |
Hi Dan_ed, nobody else aside from Jean Constant Verdier did combine these three effects with one very simple device (two magnetic rings of large diameter (in fact former Focal 15" woofer magnets pre-1990 vintage):
- a true eddy current brake on very large diameter to stabilise the movement
(which in fact is not really bearing friction, but acts in that way WITHOUT any noise added).
- vertical bearing elevated by magnetic force.
- further vibration damping on large surface-diameter of turntable platter (underneath) by magnetic force.
That is all I meant.
I have yet to see another turntable offering these three technical aspects with one simple design feature.
The thread was about bearing friction being applied to stabilize movement. Not comparing turntables regarding their "sound".
Here is one TT doing this AND combining the measure to achive some very nice side-effects.
I am certainly not going into any discussion about sonic pros or cons on this or that turntable.
I would be fruitless anyway.
This is - as always in audio - a subjective field alltogether.
My comment is about unique technical features being combined.
In no way do I want to promote the Platine Verdier here (especially so, as the current model no longer do indeed feature these 3 merits in the way the vintage model does).
There are several TT designs with good points and decent performance around.
All have their merits - all have their flaws.
Thats all. |
Dertonarm, Are you saying that the vertical magnetic suspension of the La Platine per se simultaneously offered a form of eddy current braking of the rotation of the platter in the horizontal plane? If so, why would that not also be a feature of the current version of the La Platine? (I am going to check my physics books to verify that such a phenomenon would occur, but for now I accept the principle, if that's what you meant.) |
Lewm, two magnets rotating in a horizontal = planar sphere do indeed produce an eddy current field.
The Platine Verdier folks and dealers will hate me for this .......anyway:
The current La Platine does feature somewhat lower quality magnets (compared to the old Focal magnets used till 1990/91 - that particular magnet was no longer available when Focal changed to the "6-tablet-magnet" - design invented by J. Mahul for the 15" woofers in early 1991) - thats why they promoted the ball to be inserted in the top bearing shaft hollow. To stabilize the vertical movement of the platter (in mid-90ies production was a tendency to instable magnetic field and often in loss of magnetic force causing many Platines in europe (and I suppose elsewehere too) to "oscillate" (= being unstable in height of platter)). To solve this problem the "top ball bearing shaft" was introduced (well, the hollow was there before, so they just put in the ball - smart move). That particular problem never occured with pre-1991/92 Platines. However the eddy current brake effect is no longer as dominat as it was in the original version with much better and more homogenous magnets. |
Thanks. Very interesting, indeed. I do recall hearing rumors about La Platine platters "falling down", due to loss of magnetic field strength, but none of my (two) friends who own the table have had that problem. There are a few other brands that now sport magnetic suspensions, but as far as can tell from photos, none of those has magnets of nearly the same size as found even in the current La Platine. Nor are the platters as massive. |
As to my knowledge all La Platine Verdier sold after 1995 do already feature the ball supported bearing. So those can't actually "fall down", as the vertical position is already determined by the ball bearing and no longer by magnetic force. The Platine verdier was imported and introduced to the USA fairly late (it was originally a DIY-project presented in french L'Audiophile magazine (with detailed schematics and description how to built) in the late 1970ies and the first offical built retail version was tested in summer 1980 in a german magazine). I do not know, whether there were any Platines delivered to the USA via the offical importer before 1995. |
Thanks for qualifying your position, Dertonarm. I understand now that you are referring to a specific approach taken by Verdier. That approach as you have outlined it does seem to be unique, but costly and hard to control from a manufacturer's point of view. As you documented there were other issues with this approach, so perhaps it wasn't all that to begin with. Seemed to be a good idea.
The eddy current breaking is a solid, proven approach. The problem is that it still seems to be beyond the financial means of most of us, so we are left with belts or idlers. To Chris's point, the non-compliant mylar belts and lower torque motors do sound very good. This type of belt along with a decent control mechanism can provide speed stability that is better than most belt drives and I believe it is very close to your average idler. I suspect this is because we are starting with a no-cog DC motor and the mylar provides a much tighter coupling to the platter than any stretchy belt. But that is going off on a different topic.
If nothing else this discussion should show that the designer must take the entire drive chain into consideration, regardless of whether the bearing or motor is chosen first. They still have to work together to produce a speed stable platform. |
I agree with you Dan_ed. However - the eddy current brake approach as shown by J.C.Verdier isn't all that costly. All you need are 2 old 15" woofer dirivers magnets which never suffered from shock or extreme low temperature. Thats about all you need to get those 3 features mentioned above all in one.
BTW - idler drive was introduced by and for the broadcast service turntables first. Kind of heir from the days of the grammophone. For good reason. It was of paramount importance that the platter had full 33 1/3 rpm after less than 1/2 turn. You need it for broadcast. For timing the tune played next. When direct drive had grown to full mature (by mid 1970ies the latest) the idler drive TT all vanished from broadcast stations.
Idler drive needs extreme care in execution to supply good results for turntable application. It however always gives some problems as the idler wheel itself is a source of direct noise transmission to the platter.
The idler drive is the direct counter-approach to the belt drive - one favours direct coupling between motor and platter to have very direct and immediate control over speed. The other favours as little influence and as little coupling between motor and platter as possible to minimize any possible vibration and speed shift in the motor being transmitted to the platter.
If the time frame till stable speed is actually reach is of little to no importance, - a very heavy platter coupled by string (= little grip) and driven by a very good motor will give the most stable speed for a turntable. Huge inertia combined with "slip coupling" or a kind of "cumulative coumpond motor drive" (read: very good motor coupled via string to a platter with little grip). If correctly done, it will take fairly long to get to stable speed, but once there, the speed will be extremely constant and little changes in the motor have no effect on the speed of the platter due to the - wanted" slip/low grip of the string.
Of course, this is one of many approaches in today and yesterdays turntable design. It is however the technical engineers approach if absolute stable speed to the prime goal. And if the time taken to reach this stable speed is neglectable.
The whole scenery is worth musing about. However this approach does ask for fairly expensive components (= high quality = expensive motor and very large mass in platter and extremely precise manufacturing and tooling) and huge weight in platter. Nothing that can come cheap. |
Dertonarm, the heavy platter, slip coupling approach focuses on only the issue of motor cogging. This approach does not deal with the issue of stylus drag, or any other variability in drag. Contrary to popular beliefs platter mass changes how stylus drag affects speed but does not correct it. A massive platter will reduce the magnitude of the variation but extends it over a longer period of time. A light platter will conversely allow a larger speed variation but it enables more rapid recovery. Heavy vs. light platters exhibit different sounding degradations but they are still degradations.
Intimate coupling of the motor to the platter is the only way to effectively deal with stylus drag. But intimate coupling also makes problems from cogging worse. So in the end a compromise between the two is needed. A DC motor needs less isolation than an AC motor so the compromises will and should be different. Personal preferences also will dictate the ideal compromise. For example idlers with AC motors have poor isolation from cogging, but more intimate coupling. The result is excellent rhythm and timing but finesse and low level detail are sacrificed. Some like the idler compromise and others don't.
If you start with a very low cogging motor then a better compromise can be achieved. |
Dertonearm, I don't know whether you have already done so, but you might like to go over to Vinyl Asylum and search on the musings of Mark Kelly, a very smart fellow, on the various platter drive mechanisms and their pros and cons. Of additional interest is his work to develop drive systems for AC motors that reduce motor noise and cogging. |
Dear Teres,
stylus drag is only an issue if the record is not firmly clamped down to the platter.
If the record is not firmly clamped down, we do not need to talk about correct application or technical issues anyway. This is basic parameter. If securely clamped down it becomes part of the moving system and its mass - hence: heavy platter with high inertia.
As I said before - this is only one approach and certainly not the only one in igh-end audio, but it is the approach of physic and technical engineering.
A heavy platter will have no variation once it is on speed.
Any possible loss in speed is avoided before it occurs - by correct allpied coupling with string (= very low grip but enough to avoid loss of constant speed). Thus the error does not occur but the only task for motor and string is to hold the speed - nothinh else.
Stylus drag do only have an effort when the record itself "slips" on the platter surface (and believe me - I do use a cartridge which really can "drag". But of course it is only going on a record which is firmly - really firmly - pressed down on the platter).
Sometimes it really helps illustrating forces in motion with vector diagrams on a sheet of papaer. Visulising what really is going on does set some points clear really fast.
This is physics - thus it can fairly easy be determined when you allow the facts to spread.
Trying to correct any variation in speed as fast as possible ............
The result is constant back and forth in speed.
In other words - you implement unstability by doing so.
Every technical engineer into dynamics or constant torque will tell you that this is futile.
Turntable is pure physics - not taste, not opinion.
Too often in High-end audio people get the impression that physics laws have been invented during the development of audio components.
Not so.
Extremely few audio components - mechanical ones like tonearms, cartridges and turntables - do really take correct applied physics into account.
Otherwise we would have much more better components around. |
Dertonarm, we are talking about physics. The issue of stylus drag has been hotly debated before. It is a fact that any drag, regardless of how small will slow a platters rotation. A large platter mass spreads the variation over a longer period of time, but does not and cannot eliminate it. It's basic physics. Any amount of energy added or removed to the system will directly affect speed.
Now what can be debated is the audibility of such a small effect. Logically it seems quite implausible that a force as tiny as stylus drag could be audible. The audibility of the things being discussed here certainly are in the realm of opinion and theory.
Regardless of the theory there is a great deal of evidence that techniques that target stylus drag (like bearing friction and intimate coupling) produce positive, audible results. This would suggest that the theory of audible stylus drag is correct, but it certainly falls short of proof.
Thankfully, turntable design is not pure physics. A good design also includes compromises, tastes, experimentation and even some guesswork. Otherwise turntables would all look and sound the same. Really boring... |
Dear Teres, yes, I could grant your last post with some technical counterpoints and facts, but the only result will be argument.
But I can not resist.
****Thankfully, turntable design is not pure physics. A good design also includes compromises, tastes, experimentation and even some guesswork. Otherwise turntables would all look and sound the same. Really boring...*****
Well - turntable design is pure physics.
A turntable is a rotating machine.
That rtation has to be constant and its dynamic forces have to be that large that the extraction of the modulation by the tonearm/cartridge system have no side-effect on the constant rotation.
Furthermore the whole machine has to be suspended from building resonance.
Period.
Would you argue about a wheel and its function??
Stylus drag is a very small sliding force in constant motion and is - coupled with any serious platter (of course not if the LP lays just on the platter and is not firmly clamped down) - really neglectable. Its a force smaller by several magnitudes compared to the energy the stylus puts into the platter while modulating the groove information. A force smaller by several magnitudes compared to any motor generated vibration.
It is not a magic stone nor does it inhibit mystery unknown physical energy which puts it outside the Einstein Continuum ( however - many audiophile seem to believe just this and are supported by commercial audio advertising....).
The fact that "taste, compromises, experimentation and even some guesswork" is included in the design of turntables is the reason why almost all turntables do indeed "sound" different and most do sound pretty boring.
If the NASA had handled the Apollo - Mission that way, man would have never set his foot on the moon.
I have yet to see a turntable design done right.
I have yet to see a turntable with written standard specifications to start with.
So far we have a few good amateurs, but no professional anywhere. |
Hey Dertonarm! Show us how it should be done right. Let's have a spec review. |
Hey Dan_ed, really ? I expected my post would provoke something like this. After all nobody likes big mouth with no proof behind...........
Any other Agoner interested in this ?
Specs including given reasons - or plain specs ?
Including material selection?
If some interest for this I will gladly unfold a brief but detailed enough "roadmap".
Let me know your mind.
On the other hand this is far going beyond the original thread about the bearing friction.
Maybe we should start a new thread ?? |
Absolutely. Start another thread on TT spec review, or something like that and let's see where the discussion goes. |
I'll second the motion for some discussion on these topics . . . regardless of where we stand as individuals, the enthusiast audio industry these days is very much threateaned by the stagnation of ideas, and open discussions are an excellent way to combat it (or each other:)). |
Dertonearm, You wrote, "Stylus drag is a very small sliding force in constant motion and is - coupled with any serious platter (of course not if the LP lays just on the platter and is not firmly clamped down) - really neglectable. Its a force smaller by several magnitudes compared to the energy the stylus puts into the platter while modulating the groove information. A force smaller by several magnitudes compared to any motor generated vibration."
In writing thus, you are implying that you know the approximate magnitude of the force of stylus drag. I would be interested to know what that is, so I can compare it to the magnitude of the other forces you mention. I tend to agree with you, that the force of stylus drag cannot be THAT great, since, if it were, cantilevers would be ripped from their insertions into the cartridge.
I don't think anyone would take issue with your definition of the function of a turntable. The problem is that many of us have heard or think we hear deficiencies in LP reproduction that are attributable to "something" that is at least partly overcome by the use of direct- or idler-drive, as opposed to belt drive. In this tiny little world of vinyl audiophilia, that "something" has been identified as being the result of stylus drag, because there are no data to indicate what else it might be. By the way, I don't think you meant to infer that stylus drag is a constant. Would it not be expected to vary according to groove tortuosity and distance of the stylus from the spindle? |
Lewm, "distance from the stylus"? Why would there be component that varied with this distance? Unless we're jumping to AS? |
Dan_ed, I think Lewm is talking about inner tracks vs. outer tracks on the disc. This will of course vary the amount of stylus drag torque that is applied to the platter, by a simple difference in leverage. |
Dear Kirkus, Lewm, (Teres ??) and Dan_ed, if we all join forces in this discussion I am positive that it will become a really worthwhile discurse.
Of course - stylus drag is rather a very variable force and can not really be called a "constant".
So - how do we proceed?? Do we carry on in this thread or is one of you starting another focussing on the turntable design in general, maybe with stylus drag and its influence on stability as a sidematter? Any suggestions? I am happy to participate in a real good discussion when we focus on technical aspects. |
What I wrote was that any effect of stylus drag on speed will in part be a function of the distance of the stylus from the spindle (not "distance from the stylus"). I was referring to the mechanical advantage gained by applying a force some distance from the center of rotation vs near to the center of rotation. Kirkus got it right. |
Dear friends: I'm not on the TT design ( tonearm/cartridge is my priority. ) but this discussion could help to everyone in some way or other, at least to understand what is happening.
Some of you " speak " about specs and IMHO this subject could be very controversial for say the least.
Many of the " standard " specs/measures on audio items ( any ) can't explain per-se why we hear/heard what we hear/heard.
My opinion on the subject is try to define what/where/how to measure and its relationship with what we hear/heard or our targets about. IMHO not an easy task: whom will fix/decide those " true/new spec standards "?. Anyway a good " exercise ".
A second subject: stylus drag. During our tonearm/cartridge research/design I made several tests and still doing ( for different reasons that TT design. ), one of them was this:
I choose seven different cartridges ( different stylus/compliance/MM-MC design, VTF, etc. ) and five different LP's.
The test was over the same TT and same tonearm ( at the same time. ) where the " only " variable was the cartridge ( well more than one variable due that each cartridge has different parameters. ).
The test was a " home test " not a strict controled and scientific one but interesting.
What we want to measure was how the stylus drag ( well the tonearm/cartridge. ) could change with different cartridge in different LP in different velocity recorded tracks that I choose.
What we do?: we put " that " cartridge in the tracks ( each one at the same time ) I choose ( running the TT at 33 rpm. ) and suddenly switching-off the TT and measure how many seconds take the platter to stop. I choose three tracks on one side in the LP: one at the outer of the LP one at the middle and one at the inner of the LP.
The tools I used was a cronometer, eyes and very fast " brain reaction ".
Not an easy test, I have to train for several hours ( two days ) till I " show " good " constant " response ".
This test show us that that stylus drag " exist ", that its behavior is cartridge/stylus/VTF/position on the LP dependent, that is different on different tonearms and TTs, that a heavy platter ( 20 kg. ) in rotation has an influence on that stylus drag when you swtich-off, etc, etc .
I know that maybe this almost " hobby-test " does not help on the TT discussion due that the TT was/is switch-off and that was not made it in a scientific/tools way but the test opened my " eyes " for our self tonearm/cartridge design.
It is not to easy the desing/research on " mechanical " devices ( like tonearm/TT and the like . ) specially the tests of those devices because it is not only a subject to have the know-how what/which/where/how but to have the precise scientific tools to do it: we need a laboratory and we need a lot lot of money to have that laboratory.
This issue is/was one of the reasons that bring us ( on the tonearm design ) to find where to do it, finally we meet our friend at the University and even here is not easy because is something " new " where the " scientists " does not have many experiences: it is an easy task for them nothing difficult but " new ".
Like always, I say every single day is a learning one to anyone in different areas/topics on our day by day life. There are more knowledge to discover to experience that our self ( each one ) know-how.
Regards and enjoy the music.
Raul. |
Hi Raul . . . were you able to get any comparisons of stylus drag between a modulated and an unmodulated groove? I think that's one of the central points of most of the discussion of stylus drag. |
Dear Dertonarm: +++++ " If the NASA had handled the Apollo - Mission that way, man would have never set his foot on the moon. " +++++
there is no single doubt about, everything must be " perfect " for that " job ", you can't have/make mistakes or " guesswork ".. science is the law.
In the analog audio " stage " science is still the law but the analog " world " is an imperfect one ( everywhere in the analog chain. ) that tolerate some " guesswork " in order to achve desirable targets.
There is not much research on the subject and not because there are not good audio item designers ( there are ) but mainly because there are too many " conformist and non know-how " customers: why a designer has to worry on a " perfect " design when no one is asking for? when almost no one cares about?
Almost all the analog audio item designs are more a commercial subject ( $$$$, in some ways it has to be, between other things. ) that a top quality performance to bring a top satisfaction to the customer, even the very high price items.
Where are the customers? where are we? how can the analog audio market really grow-up if we are " satisfied " with what we have? we are satisfied with the same/similar audio item designs of " 50-100 " years ago ( many times lesser designs. ), where we leave the " emotion " to explore to discover to think in a " new " way?: almost no one cares about and IMHO that's why: ++++ " I have yet to see a turntable design done right. " +++++ ( or almost any other audio item. ) we are " down " here " ( in a deep hole ) and not because there are not good " professional " designers ( there are: several. ) or people with the enough knoledge to do it.
This is not the first time that I point out these subjects and if we continue to pay for " mediocrity " that's will be exactly what we will have: " mediocrity ", IMHO I think that we need a customer " revolution ", we need to shake all those talent people out there for they give us what today we deserve, we are " the one " to make things change for the better we need to be active part of the changes.
Regards and enjoy the music.
Raul. |
I'd be interested in the discussions and ideas about turntable design and the 'pure physics' involved, yet at the same time, I'd imagine the 'real' turntable designers, those who have done the physics and actually produced a saleable commodity, laughing at us 'amateurs' wasting our time and efforts without the prospects of reaching any meaningful conclusions or resolutions?
Do we really believe that Mark Doehmann of Continuum Audio has invested 10 years of his life together with a team of 7 experts in various fields of mechanical, aeronautical and advanced systems engineering without understanding the physics involved and then testing the prototypes and manufacturing a finished workable product?
Or the Suchy family who have years of experience in turntable, arm and cartridge design?
Not to mention Harry Weissfeld, Lloyd Walker, Andy Payor, A.J. Conti, Roy Gandy and even Ivor Tiefenbrun?
And yet, for every turntable designer, there is a different solution or variation?
It is so easy for us to 'surmise' and point to the 'weaknesses' of various design philosophies but as the saying saying goes......"those that can, do and those that can't......?
Surely Dertonarm, if pure physics made it all 'black and white' and "I have yet to see a turntable design done right."?.......why have you not yet......done it!? |
Dear Raul - I do agree with you 100%. We - the customers - are indeed responsible for the products we get. Unfortunately we are a very small group inside the whole market for audio playback. As our buying power is way too small for the (global players..) industry to focus on, we do only get attention from companies which are small enough to be able (and are forced to...) to focus on a small niche of the market: - us, the audiophiles willing to spend fairly large amount of money to get satisfaction for their endless task for perfection and beauty in musical reproduction. And another "yes" - we will get mediocrity a plenty as long as we continue to buy it.
Only market behaviour will change the quality of the product. Nowhere as true as here in "our" market. |
Dear Halcro,******......."Surely Dertonarm, if pure physics made it all 'black and white' and "I have yet to see a turntable design done right."?.......why have you not yet......done it!? "******
I did.
Almost 20 years back. Together with 2 collegues I have designed and built (and they have been sold) 15 units and it did costs me alone approx. 230 000 US$ back then.
However - it was a turntable you simply could NOT sell through any High-End store due to size, weight and technical periphery needed.
The infamous WAF was way below zero. The technical features - brief summarize: a 100 lbs (very complex design internally) compund platter with a still unique approach of clamping the LP - suspended on radial AND lateral air bearing with 4 bar pressure. Whole 400 lbs turntable suspended by active air springs with 0.5 Hz resonance frequency. The motor drive - in the last incarnation without any force vectors on the bearing!! - was the big capstan from the professional Studer tape-machines. This design was backed up in the research and the tests by a division of a technical university.
Believe me - I have done it the hard way. For several years. There are good reason why my former remarks were the way they are.
As for stylus drag: - stylus drag is mainly the result of the downforce on the groove (vertical vector on the groove wall). That downforce is a result of the size of the polished area of the stylus and the VTF. Frequency modulation does vary that force only ever so lighhtly. So there is a varaition in that force, but only very faintly. AS the majority of the force is constant, it does add to the "friction" - however, it does not require correction during operation (which is impossible anyway ..... as you would create an error-correction-loop resulting in anything but certainly not constant speed).
Dear Halcro, I am familiar with all the above mentioned turntables. All those people need to SELL their turntables. Thier turntables need to fit into the living rooms of fairly well doing customers (at least if bought new in the store...) with some taste and expectations in design and a better half which sometimes does have a vote too. Furthermore their is an importer (sometimes) and a dealer (soemtimes) who need their part of the financial cake too.
In the very first all these turntables were designed and built for 2 purposes:
** unique selling proposition (by design or unique technical feature) to support the 2nd purpose:
** to make money....
A turntable "done right" will be huge, very expensive, extremely heavy and will feature some technical periphery aside the turntable itself. Imagine the working bench of a large electron microscope....... then you get an idea. |
Well, I didn't read every post, but I agree, that Turntable construction is pure Physics. And like in school, not everyone is good in this, there are differences.
I am very careful with those arguments, that this and that Designer is godlike, because he is doing this "job" (whatever it is).
I heard in the last 15 years more average sounding units than I wanted to. Some are good looking, some are heavy, some are extremely expensive but at the end of day, well you know...average. Unfortunately.
Marketing can replace knowledge and when I read such stories "... sleepless nights the last 10 years because I never had a turntable here which met my expectations .... so I tried it .... and I got it ...."
A.J.Conti is one of those who do a better job, Verdier was one of those guys, too and a few others
But not everyone. |
I heard in the last 15 years more average sounding units than I wanted to. Some are good looking, some are heavy, some are extremely expensive but at the end of day, well you know...average. Couldn't have said it better myself. And I think that one of the reasons why the audio community tends to make deities and martyrs out of certain designers is because their dream of making i.e. the ultimate turntable is something we can all respect, love, and identify with. And yes, the story behind a product is a very powerful (and legitimate) incentive to buy . . . but whether or not the dreams have actually been realized in the product is of course another question entirely. And there's also the question of what are exactly the objectives of a turntable "done right"? The story that Dertonarm tells of his ultimate turntable pursuit would be a frustrating one for me, because after that amount of work . . . I would personally want to see more than 15 people able to enjoy the pleasure of owning one. I think a truly successful product should put just as much innovation and excellence into the effecient use of materials and resources, and the financial model that allows it to be produced, purchased, and enjoyed to a significant degree. But anyway, I'd like to steer the discussion more toward what we think are the biggest weaknesses in most current high-end turntables, in a general sense across the industry. Personally, I feel that the suspension/isolation systems are the huge weak spot, along with the proper control and dissipation of resonant energy between the platter and tonearm mount. |
Dear Kirkus, indeed. Suspension of ANY turntable from vibration (if possible from air vibration = sound pressure too........ but that is another story...) is elementary. It is not a question of idea, philosophy or sound preference. It is vital to isolate the turntable from any seismic vibration. That implies that the suspension should go as low as 0.5 Hz to ensure isolation from building resonance. ANY vibration will falsify the groove modulation and alter its amplitude.
Again - we have the picture of the active or passive (if possible... air) isolated work bench for electron microscope. The working conditions for that electron-microscope are almost identical to the ideal working conditions of a turntable (at least of a turntable trying to go for anything near maximal possible performance). Both dealing in similar dimensions too.
Every owner of a decent turntable - already with built in spring suspension or not - can easily check this for himself. But a Vibraplane or a Minus-K or similar benchtop platform underneath any given turntable of at least some merit. You will notice the difference right away (no - I do not hold any shares from either company mentioned....). These platforms were designed for small elctron microscopes and vibration sensitive measurement equipment. No high-end nonsense, but straight industrial devices.
Well worth a try before you spend the next grand on a 3 feet NF-cable.....
There is one other vital aspect I want to point out: energy transfer between two masses. One mass in active movement - the other serving as the (static) floor. Picture a billiard table and the ball in motion. Ever wondered why the billiard ball does roll longer on certain tables? Because there is a direct relation between the mass (= thickness of stone platter underneath the green wool) and the energy transmission between the ball and the table. The ball stops earlier on the cheap (= rather thin marble stone platter) and lighter table. Energy transfer. More of the energy of the ball rotation is transfered into the mass of the table. If the differences between the 2 masses is increased, the ( unwnated !!) energy transmission gets less and less. The ball has a longer run - it can use more of the energy given by the qeue's poke for its motion.
There is a very similar relation between the stylus and the platter. |
