Halcro
Thanks again for doing these tests they are most interesting.
I did reply almost as soon as you posted. But it seems that I have suffered from moderator silencing
I did note the dampening influence of the second tonearm on the DD but it is interesting this doesn't seem to be reflected in the filtered results which showed no change. Have I interpreted the data correctly?
Also have you made any significant changes to the platters inertia from original?
Many thanks |
Dear Tony,
Thanks for all your feedback and interest.
Surprisingly.......Ketchup and Richardkrebs who requested the testing I provided due to their keen interest.......have gone silent? |
Hi Halcro, the DD table seems to like a little more load perhaps. Notice that the filtered sine wave has a period of 1.8 seconds or one complete rotation of the platter. That could be the runout of the platter, the motor controller oscillating gently around that speed set point or the way that the app filters the raw signal. The plot of my tt shows the same 1.8 second period. Since the raw signal will show record runout every 1.8 seconds, it is an easy filter to make; but some small amount may be left in the final output.
The belt drive Raven filtered sine wave is showing the slow, gentle speed correction being made by the motor/controller- at least that is my guess. Someone who has done design work and measurements of turntables would have a much more valued opinion than mine. On the Raven, I wonder if given more time, ie. beyond the 10 seconds after you dropped the 2nd tonearm, it had gently corrected the speed back to the original set point- even if it was just 0.1%.
As for the raw waveforms, I'm thinking that one possibility might be the response of the phono cartridge. I see the similar waveform like your TT-101 on my plot- the little breaks at the tips of the sine wave. Or maybe the more likely answer is limitations of the iPhone or the app. The sampling frequency may be too low to round out the peaks. |
Hi Tony,
My 'dedication' is made somewhat easier by the free Feikert App and Test disc you recommended.
The 'Test Procedure' is quite easy and quick to perform.
A few questions you might help me with:-
1. The Mean Frequency on the TT-101 seems to be MORE accurate with the drop of the 2nd tonearm than without it?
2. Do you have any comments on the 'shape' of the 'raw' frequency sine-waves between the two tables?
Regards |
Dover.
To answer your questions.
The servo does not know if you are going to play Mahler or Beethoven before the fact, but it does know very quickly when you do. The feedback is very fast. In much the same way that we do not know where a tennis player is going to hit the ball, yet we can follow its path smoothly without over or undershoot. This is the essence of properly designed closed loop control.
The no measurable speed change comment due to stylus drag was for the SP10MK3 and was taken from their specs. The power supply current draw observation was for the Goldmund and was a clear indication that stylus drag is real and significant. It does not, I agree, quantify its magnitude but it must be big since its effect was present even at treble frequencies. It does however give us a realtime picture. ( exluding propegation delay of the servo electronics, if you want to be precise ) I have not said that there is no measurable speed change with the Goldmund.
Loop rigidity and plinth energy dissipation. Of course these things effect attack, deacy et el. So does room treatment.
You didnt use the time line for the tests. My mistake.
The Goldmund and the LO7D are two completely different machines in concept and execution. The LO7D being an all out assult on the art of DD, TT design. The Goldmund was built to a price point using a badge engineered motor. While this motor does what it was designed to do, these price constraints show. Wrapping feedback around a motor does not elevate it above its core performance.
Peace.
Halcro.
Thanks for the test results. I agree with Tonywinsc, your dedication is impressive. |
Dear Halcro, what an excellent job you did testing your turntables. Your dedication to the hobby is impressive. It looks like the DD table actually increased speed just a bit with the 2nd tonearm while the belt drive dropped by about the same amount. The magnitude of change being just at or under 0.1%. If I were to guess, it looks like you dropped the 2nd tonearm at around the 10 second mark? And on the Raven at about the 11 second mark? Notice that the speed on the DD recovers after 2 rotations, but the belt drive speed remains about 0.1% lower. As for being able to hear that differnce in terms of pace/rhythm, I don't know. Keep in mind too that this is an extreme test beyond any music- dropping a 2nd tonearm onto a platter. |
Ketchup. I like your idea of using two tomearms. I think that the test disc is 10 inch diameter, havent seen one. So could it be placed on top of a LP? Use one arm to measure frequency and use the second arm to play music on the outer track of the LP. That would be intersting.
TT-101TT-101TT-101TT-101RAVENRAVENRAVENRAVEN |
Richardkrebs
I seemed to have missed the olive branch. Was it before or after "end of story"and "for the last time".
I have continued the discussion as you have misconstrued some of my comments and not fully addressed some of my queries.
I cannot understand how the servo/speed correction system knows whether you are going to play Mahlers 2nd Symphony or a Beethoven Sonata.
You seem to be certain that there is no measurable stylus drag on the DD by measuring the power supply. This simply doesn't quantify the the stylus lag in real time that is occurring at the stylus tip.
The comments on loop rigidity and energy dissipation were put forward in the context of maintaining the attack, intensity and decay of each note. You have overlooked the fact that even if you had perfect speed stability, the attack, intensity and decay of each note can be distorted by an inadequate plinth that is not rigid and doesn't deal with the energy reflected into the platter.
It is of no consequence to me really, but you assumed I measured the variation in stylus lag using the Timeline. That assumption is not correct.
Finally, I am trying to understand how Direct Drives address these issues, but you have offered no explanation for the differences I heard and described between the Goldmund and the Kenwood L07D, particularly in speed, timing and coherency. |
Dover. I tried to get out of this thread by offering an olive branch since I sense that we are going nowhere.... oh well.
The argument that servos cause overshoot followed by a period of slowing and then repeat does not hold up to analysis. This pitch was likely put out into the market by BD manufacturers and it has taken root in the collective thoughts of the audio community.
We use servo control here almost daily on small and large machines. If they behaved as you describe the machine performance would be totally unacceptable in some cases destructive and dangerous. Servos are not fully on, fully off devices. They have response curves, gain, ramp rising and falling, dead band and frequency responce adjustments. These parameters are talored to the task. We tune then for this. Properly implemented they do not overshoot and as we apply then here they achieve a staggering level of accuracy. The same applies to DD and ironically this is proven by the scope tests I did on the Goldmund. You will recall I could see the music being played at the time on the scope, even treble information. If the servo was correcting, over shooting, correcting undershooting..etc, what I would have seen would be a series of square wave like pulses with little relation to the music as the platter acceleration/ decelleration time constant would smother the individual current draw/music waveform. (I have said before. A correct match of motor capability, platter inertia and controller) Say what you will about the Goldmund, but one feature it has is a very mechanically stable speed measuring system. This along with the servo iteslf was doing its job correctly. ( lets keep physical motor cogging out of this)
I hesitate to use the "spurious" word again, but while loop rigity, energy dissipation etc are topics dear to my heart, as you well know, they are spurious to the discussion on platter speed stability.
Wow and Flutter, stylus drag speed change. Yes I knew the moment I pressed submitt that this would draw a response. I will concede that they are both troublesome. That said as per my earlier post, stylus drag induced speed changes are below the threshold of measurement with the SP10 MK3 and most likely many other DD tt's. On the other hand the time line is ineffective in measuring your type B stylus drag because, by its very nature, its effect is transient and the time line is measuring an average.
Agree, quality power supplies are critical to the correct operation of....just about everything in our hobby.
Ketchup. I like your idea of using two tomearms. I think that the test disc is 10 inch diameter, havent seen one. So could it be placed on top of a LP? Use one arm to measure frequency and use the second arm to play music on the outer track of the LP. That would be intersting.
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I was wondering if someone with two tonearms can do a simple test with the Feikert Android/iphone app. Play the test tone with the first tonearm and begin recording. After some data has been collected, drop the second stylus onto the record and see what happens to the tone. If the app is sensitive enough, this might show how much the platter slows due to the additional stylus pressure, how quickly it recovers, and how much it overshoots. It would be really interesting to do the exact same test on a number of different TTs. |
Richardkrebs :
Let's assume we are tracking at 2.0g.
Now let's break down the stylus drag components into 2 parts - one being stylus drag due to the tracking force ( A ) and the other being the variation in stylus drag due to the variations in the music ( B ).
I measured A, not B.
A - Stylus Drag Due to Tracking Force ( assume constant ).
When you drop the stylus into the groove the high inertia TT drops 0.008%.
( By the way - this was a very conservative estimate to avoid debate, it's actually less )
Now I believe the Technics will drop by 4 times this if the servos are not on due to the lower inertia.
The Technics maintains speed because the servo kicks in.
This is no different to me adjusting the speed via the controller to account for the constant drag...except for the following -
When I bring the speed up to adjust for the 2.0g tracking force I bring it up manually until it the speed is stable.
The Technics servo will react by increasing the speed. The catch here is that the servos only react to errors or changes in load and they dont know the magnitude of whats coming, so they ramp up the response until such time as they detect the speed is too fast - they overshoot. Then they have to correct for the overshoot. This becomes a constant cycle of overshoot and undershoot. You might not be able to measure it, but it is there.
B - Stylus Drag due to Variations in Music
I cannot measure any stylus drag with the high inertia TT. I checked for variations on both inner and outer grooves.
I assume if it exists it is too small to measure.
Same argument exists as in A above, if there is any variation then your DD servo will kick in according to some preprogrammed parameters, and once the servo kicks in, again you end up with micro overshoot and undershoot - too slow, servo, too fast, servo, too slow etc
Now we can argue until the cows come home a to which is better or worse, and which cow comes home first will vary depending on the design and quality of the individual design.
Wow and flutter versus Stylus Drag
I would give equal weight to these. If I am listening to a piano concerto, I want to hear the attack, intensity and decay of each note as well as the ebb and flow of the performance.
I would also suggest that to reproduce the attack, intensity and decay of the note, then the record/platter interface and platter/bearing/plinth design and how it deals with excess energy and maintaing a rigid loop will have a major bearing as well as stylus drag. Certainly the designers of the Final believe there is significantly more energy generated than that required to move the stylus which needs to be dealt with effectively, whilst maintaining a rigid loop between cartridge and record to measure the groove accurately. Removal of this excess energy in my experience is analogous to lowering the noise floor - increased resolution, less smearing of notes.
Re the cogging : I cannot be sure that the instability I heard is cogging. I have described what I heard a the response to Lewm which was posted prior to your last response. It may be the servos, lack of inertia or other issues, but I would add to your comments that cogging can be induced by poor power supply design if the current waveform driving the motor is not maintained accurately as well as the motor itself. I have seen a number of TT's where the power supply regulation is poorly designed and literally turns on and off whilst playing.
Cheers.
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Dover I personally would like to know what your main system consists of?
There is a reason for this
Lawrence
Fidelity Forward |
Lewm - in my posts I have tried to relate what I hear with the design etc. Some folk misread stuff. I am not anti direct drive or any drive. What I have heard in very good systems is that there are very few DD's that dont sound awful, by which I mean grainy, grey, music dissembled, fragmented, a lack of dynamics and transparency. The only ones I've heard that dont sound awful are the SP10mk3 and L07D. The Goldmund I heard had a rebuilt and upgraded power supply, many other upgrades and was in very good state of tune. The standard L07D demolished it - demolished it. Demolished it in terms of speed and timing. The Kenwood sounded more lucid, crisper and cleaner. I use this example to illustrate that in my view if you are running direct drive it needs to be at the level of the SP10mk3/L07D at least or you may be better off with an idler or belt drive. Ironically the Goldmund would probably pass the Timeline test, so the Timeline test is very valuable to give you assurance that the basic speed is accurate and maintained, but then we get into the dirty unknown. What happens in between at the micro level.
I have made a statement supported by physics that the high inertia of the Final will result in deceleration due to stylus lag variation of 1/4 in magnitude of that of the Technics SP10mk3 and Kenwood L07D. Furthermore results that quantified the stylus drag with and without the stylus playing are at a level less than the wow and flutter levels of the Technics SP10mk3 and Kenwood L07D.
A counter argument has been proposed that properly designed servo speed correction is a fundamental requirement for any TT. No numbers or empirical evidence have been put forward.
This is the nub - both the Final and the SP10mk3 are 2 of the best TT's made, they are at or near the top of the tree - so the question is what if you cant afford or obtain the top of the tree? What compromises should you make if you are going to make any ? Most think that what they have is the best. My nature is to try and understand why things sound the way they do. I have been able to improve my system by doing this - understanding what I have, its design construct and selecting products that achieve the goals which for me are important, speed, timing, coherency, harmonic structure. I personally dont have perfect pitch, but I'm extemely sensitive to timing - if the timing is off, I cant stand the music, fall asleep, lose interest.
The posts here that have references to gear I might have heard, hard facts are valuable and enlightening. Recent examples are Halcro's speed testing and Mosins' debate on belt creep which led me to study up previous posts and discussions on vintage idler motors, which was informative. Folk shouldn't get offended by posts - just get pissed off enough to go away and do some research. We all learn from this process. |
Dear Dover, I have no issue with anything you say, where it's a matter of opinion. And I believe you are totally honest when you relate to us that there is something about the "sound" of the direct-drive turntables with which you are familiar that you don't like, or you don't like as much as you like your Final. Quite apart from what Richard says, my problem with your statements is that you are relating whatever it is you don't like about DD to a known issue with all motors (cogging) or to servo effect. As audiophiles we all have the tendency to impute cause-effect relationships like this, when in fact few of us ever do the necessary experiments to prove the relationship. You may dislike DD; that's fine. But you don't know that what you don't like is directly related to cogging or servo. (In fact, which is it, cogging or servo action? You change the tune on that with regularity.)
In my system, I have a highly tweaked Lenco, a Technics SP10 Mk3, and an L07D, all set up side by side by side. They are each very different from one another in the method by which speed is "controlled". (As I have mentioned previously, the only meaningful attack on cogging is the coreless motor; L07D has that feature. But the Mk3 is just as good if not a touch superior to the L07D, with its monster "cogging" motor.) They are all superb turntables; they are more remarkable for their similarity in "sound" than they are for their differences in sound.
I hope that the DD turntables upon which you have made your judgement were properly serviced and adjusted. Leaky capacitors and the consequences of same (blown solid state devices in the speed control electronics) can take a toll on the performance of DD turntables that is not readily apparent, i.e., the table may still "work" but may not be working to its max. |
Gentlepeople
The problem with posts like this, where a difference in opinion is being aired, is that there is a tendnacy for us to talk past eachother and place significance on things that are written outside of what the author meant. This is perfectly natural.
That said I will try to clarify what I meant with my six points.
1) and 2) The Final has higher intrinsic resistance to stylus drag due to its platter which has a higher moment of inertia than the other two TTs, ONLY if you turn off their servos.
With the servo in play The SP10MK3 will show NO measurable speed change with retardation torque levels up to 10KG/cm. In their literature they use the analogy of 1000 cartridges tracking simultaenously. So we can infer from this that 1001 cartridges tracking will cause a speed change. I note that the Final slows down with 1 cartridge tracking. Lets make this clear, speed change due to stylus drag on the SP10MK3, even with 1000 cartridges in play, is so small that it is undetectable. You can take it then that I did do not acknowledge that the initial drop of in speed would be higher with the DDs. While a speed change must be there, with the SP10, it is not measurable. This is where correct matching of motor torque capability, servo characteristics and platter moment of inertia are critical.
I do not have data on the LO7D, but I expect that it would also perform well on this front.
For me the problem with speed changes due to stylus drag is that they are a function of the music being played, unlike wow and flutter which are independant of the music. Much like tape hiss, we can listen past w&f to engage with the music. This is not possible with stylus drag speed problems, as it is inside the music itself. That said it is obvious that lower w&f would be better.
Record concentricity problems are a pain especialy when one has just put down good money for a new record. But this is not a platter speed accuracy issue, so in that sense it is spurious to any discussion on absolute platter speed accuracy, even if its effect dwarfs any platter speed errors.
3)Cogging. I don't want to put words in your mouth, but I don't think that what you are hearing is actually motor cogging as in the physical effect of the motors construction. The very low frequency at which actual cogging occurs is, I suspect, not what bothers you. I do agree that there is a problem with many DD's, but it is not physical motor cogging and it can be fixed. (Maybe the Goldmund should be outside this comment.)
4) 5) Stasis torque levels. The platter will speed up if the torque output from the motor exceeds that requied to overcome bearing friction, stylus drag and windage. Not enough torque and the platter will slow down. Drive systems revert to stasis (low maintenance ) torque levels once design speed is reached. This is taught in engineering classes. Putting this another way. Motor torque output is a function of the load.
6) You are totally correct when stating that the DDs need a lot of work to bring them up to their potetnial. This, however, does not detract from the fundamental performance of the drive method.
Lewm said "If you prefer your thread drive to any and all direct-drives you have ever heard, that is all well and good. I am sure it is superb. But I don't think you can prove from first principles that it is inherently superior to all direct drive."
Totally correct. The opposite is also true, so let's call it a day and both enjoy this thrilling hobby of ours.
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Richard
1) The 0.0008% speed impact from stylus drag I measured on the Final is insignificant in the context of the other issues raised such as eccentric records etc - the ones you believe are spurious. The measured speed change is less than the wow and flutter quoted for both the SP10 and L07D with their speed correction engaged.
2) I recall you said it was a myth that the servos are operating frequently, and I assume they only occur after the drop off in speed, which will initially be higher as you acknowledge.
3) Cant comment on cogging as I dont have enough knowledge other than I can hear it on most DD's. You have acknowledged that whilst they may occur at different frequencies the magnitude is lower with the higher speed motor.
4) Pass
5) I dont believe much of what I read. Having studied engineering at the University of Auckland it is easy to identify the contradictions within the brochures. For example, as you have alluded to, there is no way the Technics would support the load of 1000 tonearms without the speed correction being employed.
6) No doubt there are many paths to enlightenment, but you haven't convinced me that speed correction is required on all turntables, which was your original assertion, based on your observations of the performance of a Goldmund Studio which I believe is a very poorly designed turntable.
Yes, thank you, I have enjoyed the Final for over 20 years.
It has not required a new plinth, redesigned power supply, additional mats & clamps , or any further expenditure to address inherent design issues.
It continues to be state of the art some 40 years after production commenced. |
Dover, Perhaps SP10-mkIII has a foot in both camps for good reason...
^ Brady, Chris (2008-10-06). "Teres MicroPrecise Speed Technology PDF". Retrieved 2009-01-15. "Dealing with stylus drag is another important aspect of a quality turntable drive system. It would seem that the tiny forces exerted by the stylus would fade into insignificance. However, given our extraordinary sensitivity to micro speed variations, the uneven force from stylus drag is audible and degrades sound reproduction. With a microscopic view, loud passages slightly slow the platters rotation. Contrary to popular beliefs platter mass changes how stylus drag affects speed but does not counteract the effects of stylus drag. 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 quite different sounding degradations but they are still degradations. We find the longer shallower variations that result from a heavy platter to be more benign. However, there are others that prefer the degradations from a light platter. The point is that stylus drag causes degradations that are changed but not eliminated by platter mass. The only effective mechanism for truly reducing stylus drag effects is application of torque from the motor. Increasing the available motor torque makes stylus drag proportionately smaller and therefore will result in a net reduction in the effects of stylus drag. However, increasing torque usually will at the same time increase cogging. Once again we are back to the need of finding a balance between two competing objectives. To further complicate the situation a compliant coupling between the motor and platter reduces the motors ability to control platter speed. Any compliance between the motor and platter causes a delay in the delivery of torque. When a rubber belt is used additional torque from the motor will cause the belt to stretch. This energy will eventually be delivered to the platter but only after a time delay making it impossible for the motor to compensate for short term effects of stylus drag."
From this, as an analogy, a bit like a steam engine...applying the brakes did not slow it down sharply, only a little, but the lower speed stayed for longer... |
Dover, Final Audio High inertia TT has a resistance to stylus drag variation 4 times higher than the SP10mk3 & Kenwood L07D Yet you already admitted that you have to reset the speed on your Final Audio TT to accommodate for stylus drag? So my test procedure was :
1. Set the speed with the KAB with no record playing.
2. Use the Timeline to validate the speed at both inner at outer grooves.
3. Reset the speed again with the KAB with the record playing tracking at 2g
4. Use the Timeline to validate the speed at both inner at outer grooves.
Now I'm reasonably happy about the need for belt-drive decks without monitored speed correction.....to be set up for 'stylus down' accuracy. But I have yet to see (via video)......a belt-drive (even with massive inertia) pass the Timeline test with and without stylus in the groove? I think you agree with that:- I think your test methodology would prove that only turntables with error speed correction built in will pass. We know that stylus drag exists and should always set speed with the stylus playing. So I'm not quite sure where you're going with this 'High Inertia' argument unless you can demonstrate differences in the effect of 'stylus drag'? Regards |
1) The Final has been shown, through your own testing, to slow down due to stylus drag.....end of story
2) You are quite right, the Final has much higher intrinsic resistance to stylus drag than the other TT's mentioned...if you assume that the others have their servos disengaged
3) Cogging, if present, at 11hz for the DD example you gave would be easily mitigated by a correctly operating servo. The corresponding frequency for the thread drive you mentioned would be around 120hz, with no servo present to corect. I leave it up to the listener to decide which frequency, would be the most benign. If you are talking about what I call "jitter" a much higher frequency artefact common on DD's, you will have to wait for my upcoming web site to see how it is addressed.
4) You need to revisit your laws on motion to see what happens to ANY drive system that does not reduce torque to stasis levels at design speed.
5) Regarding the 1000 tonearms, phase switching, full cycle detection FG, double servos,SPZ, high kinetic energy of rotation, sine cosine, et el. you shouldnt believe everything you read in sales brochures. They are, afterall, trying to seperate you from your money.
5) Hopefully, for the last time. There are many paths to enlightement. You like the Final, thats great. Enjoy the music it plays. This hobby of ours in not a competition. |
I looked it up and now know Techdas is Japanese. "Techdas" sounded German to me. |
This is the way of the turntable world: manufacturers have made their choices between hi and lo mass and hi and lo torque, and between direct-drive and belt-drive (and idler-drive). Then comes the technical justification for what each has done. Techdas, as you know, is by far not the first manufacturer to choose hi-mass platter combined with lo-torque motor. I think the first guys to go all the way with that were Lloyd Walker and David Fletcher (Nottingham Analog). The consortium in the American West that gave rise to Teres, Galibier, and Redpoint can also take some credit. It is merely up to us to listen and choose. Chronologically, I don't know where Final Audio fits; perhaps they were leaders too in implementing that idea. (Is "Techdas" coming from Dertonearm, by the way? I had not heard of this new brand, but I do know DT announced plans to bring a turntable to market, and he does preach very high mass/low torque.)
"The torque ripple or cogging torque will be lower"... I think a better way to put it is that the cogging of a motor spinning at 1800 rpm will occur at a higher frequency, for a given number of poles, and perhaps (really, perhaps) is less likely to be audible for that reason. But on the other hand, such a more rapidly spinning motor will be more likely to emit vibrations and noise, due to structural imperfections. Enter the belt-drive. Further, Kenwood, Pioneer Exclusive, Dual, and a few others back in the day used coreless motors to minimize if not eliminate totally the issue of cogging in their direct-drive turntables. Another wag on these pages or on VA has opined that cogging is essentially inaudible. I have no opinion on that.
Do you happen to know what is the rotational inertia of the L07D with the optional peripheral ring weight installed? I am using it with mine. Interestingly, when one uses the ring, one is also told to flip a switch on the outboard PS which I guess changes the servo so as to recognize the additional mass.
If you prefer your thread drive to any and all direct-drives you have ever heard, that is all well and good. I am sure it is superb. But I don't think you can prove from first principles that it is inherently superior to all direct drive. |
Dover
With the many faults of analogue playback I'm guessing there would be few on these forums including those in the audio press that would debate stylus drag as a principal fault, but maybe I'm wrong.
Speaking for myself I think this is why experimenting with some vintage direct drives has started me on a better path to enjoying more from my records then ever before and at a fraction of the cost of my previous belt drive tables.
More on serious faults as you are well aware, another speed instability problem that grossly effects pitch is off centre spindle and worn holes which effects pretty much every record causing velocity changes.
:pitch rules:
These new fancy tables of today ,that is, the ones you would take a mortgage out on,.Do any of these new age designers tackled this problem. The wow from a off centre record can be significant, worst then a warped record.
A while ago one of these table manufactures put up a dramatic test on youtube I think, featuring several people rapping on the platform of his $150,000.00 ,less arm, table while it played! Anyone here ever witness Mich Cotter in one of his demonstration's doing basically the same thing............ 30 years ago.
Finally for those with a LO7D that want to use a Time line,you can easily fabricate a disk to fit over the spindle of the table and set in a second spindle that fits the hole of the timeline.
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Richardkrebs "The perfect TT has absolute speed stability under all load conditions" I would draw your attention to the following : Newtons Second Law of Motion - Force = mass x acceleration or Acceleration = Force/mass In other words deceleration due to an external force is inversely proportional to mass. The moment of inertia for the following TT's are - Final Audio high inertia TT - 3920kg/cm2 Kenwood L07D - 1025kg/cm2 Technics SP10mk3 - 1100kg/cm2 This means that the high inertia Final Audio TT requires a 300% increase in stylus drag variation compared to the L07D and SP10mk3 to achieve the same loss of speed. In other words for a given additional force due to stylus drag variation the Technics SP10mk3 and Kenwood L07D will have a deceleration 4 times higher than the Final Audio high inertia TT. Now if we look at the design intent of both the Technnics and Kenwood we find some interesting facts : Kenwood L07D Manual
A moment of inertia of 1025kg-cm2 is obtained ( when the turntable sheet is attached ), resulting in high kinetic energy of rotation. Therefore the platter rotates stably even if the transient load from the stylus varies.
The L07D uses double servo coupling which automatically switches the control method when the speed difference is beyond +-3% from the rated speed: when the speed difference is beyond +-3% the speed is controlled to obtain a large torque and, when it is less than +-3%, the phase is controlled to obtain a wide lock range and large phase gain Clearly the Kenwood designers believed that the magical figure for moment of inertia of 1000kg/cm2 was sufficient to overcome stylus drag fluctuations. Now let's look at the Technics SP10mk3 Sales Brochure Technics SP10mk3 Brochure
1.1 ton-cm2 Moment of Inertia
Huge moment of inertia results from the 10kg platter made of diecast aluminium with a 15mm thick copper alloy surface layer. Therefore there is no change in speed with any fixed load up to 10kg-cm equivalent to 1000 tonearms tracking at 2g each. Of course, the real benefit is that the platter keeps rotating at exactly rated speed even if you accidentally touch it during play.
Wow and Flutter 0.015% WRMS, Speed Accuracy +-0.001%
Besides the huge moment of inertia of the heavy platter itself, our full cycle detection FG also contributes to rotational accuracy by supplying a more reliable signal for phase comparison with the reference So the Technics designers have a foot in both camps. On the one hand they believe that a moment of inertia of 1100kg/cm2 will support 1000 tonearms tracking at 2gm but then they go on to say that the fast error correction helps to maintain speed. Furthermore the Technics SP10mk3 Brochure also explains that purpose of the high torque motor is to ensure for that the platter can be brought up to speed within 0.25seconds and reverse torque can stop the platter in 0.3seconds to meet the requirements of Radio Stations. With regard to your comments on the Techdas, I would draw your attention to the design. Although the Techdas has a 30kg platter, the motor drive is low torque. They deliberately drop the torque as low as possible just to keep the platter spinning accurately and no more. They have done this to minimise noise and vibration. This is explained on their website. To reiterate my earlier posts on cogging - The torque ripple or cogging torque will be lower on a high inertia thread drive because a Direct Drive motor is running much slower. For example DD - 33.33rpm x 20 poles = 20 poles per revolution of record. AC/thread drive - 1800rpm x 4 poles = 216 poles per revolution of record. In summary then, the benefits of a high inertia thread drive over direct drive are : Final Audio High inertia TT has a resistance to stylus drag variation 4 times higher than the SP10mk3 & Kenwood L07D Final Audio High inertia TT has less cogging effect ( and lower amplitude ) due to the higher motor speed. Speed correction is required on Direct Drive TT's due to insufficient moment of inertia which is required to resist to transient load fluctuations. |
Hi Chris,
I will be testing azimuth and arm resonances via this App when I get some time?
Seems like a pretty good investment for under $20 incl delivery from Dr Feikert?
Gotta love the audio community? :-)
Regards |
Hi Tdaudio,
I tested the Raven with one, two and three motors using the Timeline......and two motors gave the most stable and consistent speed using this method? |
Halcro, thanks for your interesting post. I wonder if you would get different test results on your Raven if you used one motor? Any thoughts? |
Hi Tonywinsc/Henry et al. Thanks for publishing that excellent information Henry ! From Dr. Feickerts website. ------------------------------------------------------------ The optimal Azimuth can be found reliably using a systematic analysis of the values of level and phase angle of the crosstalk signal against different azimuth settings.
But this is not the complete functionality you get. You can also measure dynamically using Pink Noise to see how your cartridge reacts under complex signals. Additionally you can measure the frequency response of your cartridge/phono-stage with Pink Noise (dynamic) or with a sine-wave sweep (static). In both cases also in left or right channel only mode.
Setting up turntable speed now is an easy task as you dont need to use inaccurate strobe discs. Simply use Adjust+ and enjoy additional benefit from the built-in wow&flutter analyzer now even evaluating according to DIN IEC 386 (formerly DIN 45507)! Now you can test how good your turntable spins your discs
. ------------------------------------------------------------ To All. Would I be correct in assuming that if we wanted a real apples to apples comparison of the data, turntable to turntable then Halcro (Henry) needs to use the same tonearm/cartridge on each table ? Did u use different tonearms and cartridges on the two turntables Henry ? From Dr Feickets website again. Btw - I am not affiliated with Dr. Feickert. Another feature is the fres task. You can measure the resonance frequency of your cartridge/tonearm combination, something very, very rarely found nowadays. Adjust+ helps you to see if your chosen combination works in the recommended range of 8-12 Hertz. Well, and if you are not sure if you have additional resonances in your tonearm resulting from tracking you can measure in the range from 30 to 500 Hertz and see
.. Back in the 70- 80s when vinyl was at its peak, Bruce Thigpen did a number of wow and flutter tests, without an Android or I phone :^) ........ on various tonearms using the same table. But this a turntable thread... Cheers wow and flutter defined |
Also note that even if your speed is off by 0.1Hz, it will take 945 minutes of running time for your platter to gain/lose one rotation. Nothing against the timeline, just that your turntable would have to run for almost a day with the timeline to see how accurate it is. These plots show you results in a matter of seconds. It's not quite that bad. If your TT is 3' from the wall and your laser deviation is 1.5mm per revolution, your speed is off by 0.1Hz. 1.5 mm may be hard to see, but if you let it run for 10 revolutions and divide your total deviation by 10 you should be able to determine a 0.1Hz error pretty easily (if you have my Timeline Calculator Excel file that I posted about in this thread): http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1327029459The phone app sounds pretty cool, though. It is actually not just an iPhone app. I just discovered that you can get it for Android devices, too. I may have to try it out. |
Note the almost perfect Mean Frequency Response against the recorded 3150Hz and the impressive .01% speed deviation. It makes you wonder if you're measuring the speed stability of your turntable, the lathe that cut the test record, or both. Perhaps this is a benefit of the Timeline. Your measurements are not hindered by lathe inaccuracy. There has to be some lathe inaccuracy. If there wasn't, wouldn't we all be listening to records on lathes or turntable with record lathe type drives? If your Timeline was 31" from a wall, a speed error of .01% would appear as a 0.02" (0.5mm) laser deviation per revolution. |
I see variation about the setpoint which is normal. That is the speed control system working. The DD table has a funny pattern to it. Notice the two bumps and then a flat line in the speed plot? The DD table speed control seems to do a correction over about 10 seconds and then rest. Then the cycle repeats. The Raven on the other hand has a pretty constant cycle about the speed setpoint which is very similar to my table. Note that these corrections are within 0.01% to 0.02% of speed. Very fine control.
Also note that even if your speed is off by 0.1Hz, it will take 945 minutes of running time for your platter to gain/lose one rotation. Nothing against the timeline, just that your turntable would have to run for almost a day with the timeline to see how accurate it is. These plots show you results in a matter of seconds. |
Hi Tony,
Yes....the Raven is belt-drive.
I'd appreciate it if you could explain to me what you can see in the different plots.....as I must admit....I'm not sure what to be looking for? :-) |
Hi Halcro,
Thanks for uploading those pictures. It is exciting to see how different tables perform. First, note that the Raw Frequency plots are nearly the same on both tables as it should be. That is due to the eccentricty of the grooves to the center hole of the record. Is the Raven a belt drive table? I also see different results on my table (belt drive); but the numbers improve the longer I let my table run. Warm up time seems to be more critical for belt drive vs. your direct drive.
What is interesting too is that I see about a 5 second period in the filtered plots which is the same for my table. Since the period is 5 seconds, I would not call that motor cogging. I think it is the speed control circuits. The designers have probably purposefully put in long time constants to make sure the speed correction is slow and gentle so as not to be heard. |
I noted the recommendation from Tonywinsc re the Dr Feikert Analogue iPhone/iPad free App....so promptly downloaded it onto my iPad and ordered the 10" Test disc from his Website. HEREis the Frequency Plot from the Victor TT-101 Direct Drive deck and HEREare the Specs. Note the almost perfect Mean Frequency Response against the recorded 3150Hz and the impressive .01% speed deviation. Note also the impressive mirror-imaged sine wave plot positive and negative? HEREis the corresponding Frequency Plot for the Raven AC-2. note the lack of symmetry above and below the mean line? HEREis the corresponding Data for the Raven showing a less precise match to the 3150Hz Test Tone. This is the closest that the Raven Motor Controller allows me to get. Still not too bad? The thing these Plots do not show however.....is that every time I do a new plot for the Raven AC.......it gives slightly different results whereas every Plot for the TT-101 is identical. Whereas this information may have some value to the academic or scientist......I find the Timeline to be a better indicator of both short-term speed drift as well as long-term speed maintenance. The only disparaging remarks about the Timeline I find....comes from those who don't own one....or those whose turntable performs poorly against one? :-) |
Another observation that I should note: The record has a much bigger, broader soundstage so the drums sound further away. The CD soundstage being smaller makes the drums sound closer more immediate. I know it is not the case, but it is like the band recorded the song in two different locations. Which one is right? Maybe I shouldn't have both versions. As per the old adage; man with two watches is never sure what time it is. |
I just did an experiment using the first track on Fresh Aire III. Some great drums and synthesizer on that track. I have both the CD and the record so I listened to the first track back to back. I focused on the bass. I found that the bass on the CD is just a bit crisper and deeper. Not a big difference but it is there. So is my tt deficient? Is the difference due to speed stability, cartridge, tonearm or tubes? My preamp tubes are a couple of years old now. |
Works for me too. I invite anyone to come listen to the Appassionata on my tt and tell me what's wrong with it. I don't mind constructive criticism- except that it ends up costing big $$$ in upgrades. :) |
Most suspended tables have the motor fixed and platter/arm suspended to isolate the arm from motor vibration. that was the problem with wimpy suspension which would create oscillation and speed changes. This was especially true with suspensions that hold the plinth up, rather than when the plinth hangs, such as Oracle or Sota. Sota was able to fix the motor to the platter/arm plinth by changing the motor and regulation to virtually eliminate motor vibration and damping what was left. Works as far as I can tell. |
Yes I imported & distributed SOTA in this country about 25 years ago. |
Yeah. The bass on mine was muffled as well. (I totally forgot about that issue.) Could be I had the version you are talking about. But when you say "we", do you mean to say you were a SOTA dealer or otherwise involved with SOTA? |
Lewm - the "cogging" mostly showed up as instability, most apparent in the bottom end. This was cleaned up with the updated power supply & on board regulation. This was consistant across many SOTA's we sold at the time. Sounds like you had a different issue. |
I don't think "cogging" had anything to do with the wavering pitch of my old SS Sapphire. Possibly the mounting of the motor on the plinth whilst the bearing and platter were suspended did have something to do with it. I think that cogging, if indeed it is audible at all in any well designed TT motor, would give a "regularly regular" type of distortion and would probably not affect pitch so obviously. I actually heretofore thought that what I heard with my Sota was due to the old stylus drag/belt stretch bugaboo, but that's just an unsubstantiated guess.
Interesting to note that the original AR turntable, which I used for years, also had the motor mounted on solid ground and the platter suspended. Yet it is touted as a "classic". I can't even remember whether it gave an accurate rendition of piano notes. |
Lewm - same experience, but from the motor & power supply mods we did, the cogging in the early motors on the SOTA was significant. According to our tech the "cogging" was induced by shortcomings with the power supply regulation on the papst motor board, not the traditional cogging as in poles/slot rotation of the motor itself. That being said, the motor/platter should be rigidly coupled for stability, and obviously SOTA addressed this issue later by mounting the motor on the same chassis as the platter & arm.
After the SOTA I temporarily used a Townsend Rock with the ET2 and the stability of the fixed plinth design was apparent, despite the sloppy build quality of the early Townsend. |
Yes, the modern Sota uses an AC motor and electronic power supply in lieu of the previous DC motor. My Cosmos IV seems dead on, and since the motor is mounted to the same suspended sub assembly as the platter and arm, there is no movement between them, unlike most suspended tables where the motor is fixed and the platter/arm is suspended.
Still no comment on my interpretation of the Fat Bob's video after dropping the cartridge? |
Dear Dover, That was a nice post. But as regards your "old" Sota Star, I had a different experience with my old SOTA Star Sapphire Series III. I owned it from about 1990 to the late 1990s. This was the turntable that made me a believer in the potential deficiencies of belt drive. I could easily hear the pitch instability, particularly on jazz and classical piano LPs. For all that time, I put up with it, because I thought that the distortion I was hearing was on the master tape from which the LPs were made. (There was no internet in those years to tell me I was wrong.) Then I bought a Nottingham Hyperspace, which is not too different from the SS in design philosophy but is worlds better in its accuracy of reproduction of piano music, i.e., pitch stable, elastic belt drive notwithstanding. When I added a Walker Precision Motor Controller to the Hyperspace rig, everything went up a notch further; the Walker made a huge improvement in what I already liked quite a bit. These experiences led me to begin to appreciate the importance of drive mechanisms and the proper job of a turntable. I hasten to add that, from what I have gleaned second hand, the modern SOTA turntables are also much improved over my old Star Sapphire. I mean no slur on their current products. |
Dover
No inconsistency at all. I have repeatedly said that there are many paths...,
Obviously within each family of drive there is bad and good engineering design.
Further I have tried to be as generic as possible in my posts. I mentioned the Goldmund only because it gave me a first hand view of the effect of stylus drag (which was astonishing in its magnitude).No other reason. I mentioned the SP10 mk3 only because I had the moment of inertia figure for its platter and I made no comment on its goodness or otherwise. It was simply to illustrate what moment of inertia meant and to quantify it.
I am quite familiar with the LO7 D, it is indeed a well built machine.
The discussion on arms carts etc is spurious as it is outside the realm of this thread. I agree they have an effect on perceived speed stability and that they place different demands on the TT and its drive, but what we need is a platform that is speed stable in the first instance.
We are talking about drive methods and their various features and failings. They all have failings, hence my comment re the type, that in the opinion of the listener is the most innocuous.
"The perfect TT has absolute speed stability under all load conditions".
I have also been consistent that in my view that a well designed closed loop speed control is required if we are to approach this goal. This regardless of the drive method employed, the platters moment of inertia, motor self correction characteristics or its torque curve.
While technical specs are limited, the TechDas TT ( a refreshing take on TT design) .with a platter approaching 30 kg and a high moment of inertia. With a synchronous AC motor and belt drive....Appears to have closed loop speed control.
If this is so, it seems that I am not alone in this view and that the the designer considers these small changes in speed to be musically important. |
Dover... great writing and I can agree with most of what you wrote...
Robert fulton did do testing and experiments and of course most important listening ...his conclusions where that hi profile line contact elliptical ect etc... in a pivoted arm causes "lots" of distortion (audible)due to the fact of cantilever twisting...and in fact maybe do to hi freq phase anomalies because of the twisting
moreover you maybe right on why we hear differences in everything because of the servo/drive/electronics etc..
please carry on
Lawrence
Fidelity Forward |
Richardkrebs, A simple dynamic load test you might want to try if you havent already done so, is to hold your finger against the rotating platter while playing music. I'm not sure how relevent this is - the force reative to the incremental change in stylus drag has not been quantified. In my earlier post I quantified the impact on speed due to the stylus drag differential between stylus not playing versus playing, with my high mass thread drive. The Final TT has a 20kg platter with offset weight distribution, it is around 3920kg/cm vs your 1100kg/cm of the SP10mk3 (10kg platter). Most DD's would have substantially less than your SP10mk3. The speed change with and without the stylus playing was approx 0.008%, so presumably if there were variations in the drag due to musical peaks and troughs then the variation it would be a very small small proportion of this. You would have to agree this is tiny. So the issue becomes what is happening at a micro level. The thumb test is not measuring this micro behaviour. To me the nub of the issue is what is happening momentarily. If the direct drive has less inertia than say a high mass thread drive, then it may have a bigger momentary drop in speed, but its recovery might be quicker if properly designed. In this scenario we clearly have big speed drop/quick recovery versus small speed drop/slow recovery. Now an interesting comparison here is your old Goldmund Studio versus the Kenwood L07D - both DD with speed correction, but with different feedback behaviour. Did your old Goldmund Studio pass the thumb test. I doubt it very much. You could hear the poles ( 8 pole motor from memory ) as they slewed past the start line. The Kenwood L07D blitzed it in timing and microdynamics. Ironically the Goldmund would probably pass the Timeline test as would the Kenwood due to the speed correction. As far as music reproduction goes they were on different planets. Interestingly if I recall correctly the Kenwood trumpeted "Transient Load Fluctuation" in their manual as opposed to "wow and flutter". Again the method of drive/ control comes into play here and we each need to decide which does the least harm. Here you seem to have shifted your stance from an earlier post of championing good design to one of "choosing the method of drive that does the least harm". I would argue that it is the quality of the design irrespective of drive as in the Goldmund/Kenwood example above. There are other factors in speed. I tend to judge a system by its speed and coherency. Many systems are not that quick or coherent and the speed and coherency of the front end is masked somewhat. As Tonywinsc has quantified eccentric records can have a significant impact on speed and timing. Cantilever design now comes into play. I have a new Koetsu Black Goldline ( shelved ) and a friend has a new Koetsu Rosewood - both of them slew around on eccentric records. Having had many Koetsu's over 30 years I suspect they have screwed up the cantilever design integrity somewhere along the line. Mismatched arms/cartridges in terms of compliance mismatches may well skew speed and timing. Interestingly Bruce Thigpen argues that his Eminent Technology produces less distortion on eccentric records than a conventional pivoted arm. Stylus shape may well have an impact on speed and coherence. There is an argument that a spherical stylus will have less phase errors than a fine profile tip. Phase errors will skew timing. Tangential tracking versus pivoted arms - again the tracking error of pivoted arms may skew phase & timing. An example of this was my old Sota Star/ET2/Denon 103 Garrott - very very good speed and coherence despite the rubber band drive. Yes the motor regulation had been worked over to reduce cogging somewhat. But I am resonably sure that that front end had much better timing than say any Technics SP10mk2 or Goldmund Studio I've heard and I believe that the sum of the parts including TT, tonearm and cartridge all come into play if we want to talk about musical timing and coherence. Let's face it no one wants DD done badly, Belt Drive done badly or Idler done badly and unfortunately most of them are, irrespective of cost. To use a hackneyed phrase - there are no free lunches when it comes to good turntable design. |
Peterayer...Yes i totally agree if it was not for a lot of people on these forums starting to demand better performance then no company would be willing to invest in our little hobbies!
Manufactures do read the forums!
Lawrence
Fidelity Forward |
There is a new table called the Tech Das Air Force One which is getting a bunch of buzz over on WhatsBestForum. It has a magnetically levitated platter which I think is driven by a rubber belt. Bob Graham is importing it as the NA distributor and likes it so much that he is developing a new 12" arm called the "Elite" for the table. Two samples are at CES now. It's nice to see that someone is developing new, seemingly very well engineered turntables these days which are reaching for the state of the art. The NVS is DD and this one is belt. It will be interesting to see how they compare long term to some of the classic vintage tables discussed here. |
I was trying to be supportive. I think the availability of the Timeline has created a furor that is completely out of proportion to its real significance. A case of too much information. |
