Halcro -
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. The question then becomes how significant is stylus drag variation, should we speed correct, and if so how. Remember also that the timeline is only a sampling of 1 per revolution, what is happening in between that interval is unknown.
You could have Turntable A that has a much bigger variation when dropping the stylus than turntable B but has a better instantaneous speed correction. Which is better for sound reproduction ?
We also know that the natural recovery of AC motors and Brushless DC motors if the motor "slips" due to back emf and goes out of phase slightly that the recovery is different - some say the AC motor recovers sinusoidally whereas a DC motor tends to recover trapezoidally. Can you measure this ? What difference does it make to the sound ?
Lots of unknowns here. |
For what its worth I rate the Idlers as my favourite.
I too have owned belt,dd and idler, and as good as my last dd sounded (slate plinthed Technics SP 10 MKII), it just wasn't as musical as a modded Lenco 75 I now use. |
Dover,
what table are you using for those tests, would be great to see an actual video like Halcro provided. |
Dover,
The only visual test for 'stylus drag' using the Timeline.....is to have the turntable operating with the steady stationary flash on the wall WITHOUT the arm lowered...and then to lower the arm and see if the flashing light moves at all.
Raising and lowering the arm several times whilst observing the action of the flashing light will confirm success or failure? |
Dev,
The Raven AC does not perform as well as the TT-101 in regards to 'stylus drag' yet seems to be better than the Transrotor appears from the Timeline video?
For what it's worth though......the sound of the Raven AC can be just as musically satisfying as the Victor. |
Richardkrebs
Yes I agree on moving away from which is best to what do we need.
Mosins previous posts on motors used in various idler drives for example would indicate to me that you cant even put Garrard 301/401's in the same camp as say the EMT 927 - I'm not saying one is better, more that the motor drives are completely different in motor characteristics, use of motor flywheels/eddy brakes, distribution of mass in the platter etc. So the fact that they are both idlers is all they have in common.
With regard to my stylus drag testing I wanted to test two things -
1. Does my TT deal effectively with stylus drag
2. How accurate is my KAB speed checker ( assuming the Timeline is more accurate ).
I have always set the speed with a record playing using the KAB speedstrobe.
Some folk on the forum reckoned they couldn't see stylus drag with the KAB.
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.
In both instances the TT passed the Timeline test and also confirmed that my KAB was accurate. The Timeline indicated no errors when using the KAB.
As for consistancy of stylus drag - presumably stylus drag has record groove modulation, stylus pressure, antiskate forces all contributing.
All I can say is with my TT the inner/outer grooves made no difference as verified with the Timeline and with the KAB, running the record as far as it would go, the KAB remain rock steady.
I suppose the next step might be to set the speed using a flute concerto and check whether you get through a Mahler Symphony or Reference Recordings Dafos on time without speed correction to quantity that differential.
The point I take from your Goldmund example is that you are suggesting that mass alone will not provide stability with a motor that simply doesn't have enough torque to start with. |
just to recap for people that did not see my vid on rauls thread.....on how a good turntable will handle pulses from my finger which would be a thousand times more then any groove modulation!the kab strobodisk will show off this
https://www.youtube.com/watch?v=PB2TaN2FPRU
if your interested contact me
Lawrence
Fidelity Forward |
Thank you Peter,
When I saw that Timeline video using the Transrotor turntable.......it was also the first time that I was able to appreciate the effects of stylus drag.
It's hard to imagine anyone claiming that 'speed control' was inconsequential after viewing it?
Regards |
Halcro, your video of the Victor is most impressive. I'm not sure that many tables would pass that test which such flying colors. Well done. Have you tried this test with the dot falling on a wall that is further away? The video of the Transrotor tells a whole different story. It's surprising how far off that is with such a heavy platter. Someone once described the effect of stylus drag as similar to a fly trying to slow down an elephant. I no longer see the relevance of that analogy.
As interesting as a list of tables that pass this test would be, I don't think we will see one any time soon. Thanks for sharing your video. |
Viridian, you wrote:
"So......you listen to turntables professionally? Where can I apply for that job?"
sorry for my late reply. It was a kind of replic to all these guys who still believe that in the studios (so called professionals) they used pro-gear but these units could'nt be well designed or appropriate for us audiophiles. Maybe the biggest mistake ever made!
This is why some people still believe good idlers make noises only - the next biggest mistake.
I am using three other belt drives (MS and Continuum) and believe they sound terrific, not only because of the drive. I also loved my Nakamichi DD but to be very honest the best investment I ever made was my EMT R80 idler drive playing with a TSD 15 Anniversary via a Western Electric 618B SUT.
So maybe the job you are applying for is already booked, nevertheless if you are close by to Munich we could arrange an exchange, maybe I can learn something.
all the best |
and we have to remember that that ideal/perfect TT design main target is to: FULFIL THE LP/CARTRIDGE NEEDS and not only to take money for we the customers.
R. |
Halcro,
I recall your video prior on another thread and that's exactly what I'm referring to, thanks for sharing that again.
You also answered my question in relation to how many turns should it be by lowering the three stylus onto the record, doesn't matter!
So we have one table that clearly demonstrats it holds accurate speed, any others? I'm very curious to see.
Can you show the results for your TW table, non of mine including the flagship BK would hold an accurate speed. |
Dear Richardkrebs: I agree with Jazdoc too. There are several targets on a whole TT design and certainly what you posted:
+++++ " have absolute speed stability under all load conditions. " +++++
is a primary one but is only one link/part of the TT design and execution design. As you said: TT bearing is critical, platter weight and motor match, arm board design, platter build materials, plinth build materials, arm board build materials, mat ( if any ) build materials, drive system, motor choosed, TT footers, damping/drain vibrations/resonances, etc, etc.
Good to read your posts and other people ones that in many ways what we read it in this tread ( at least for me ) was/is a learning one.
Regards and enjoy the music,
R. |
The iPhone app filters out the record runout. Easy to do since record runout has a 1.8 second period. And I go right back to the record runout issue. Record speed accuracy is at least an order of magnitude worse than any high end table made today. Sure, you might loose between zero to 1/3 of a rotation during one side of record play (approx 833 rotations total). So what? Don't tell me anyone can hear that. WoW&Flutter is more critical an issue and that gets back to the motor quality and it's speed control circuits. Maybe I am wrong, but I don't believe drive types matter that much regarding speed accuracy. I think drive types affect the sound character of the turntable as much as all of the other design features of a given turntable such as plinth, mass, and dissapation of vibrational energy. If Wow&Flutter is <0.05% then it is all about the record and how the table/tonearm extracts the information. I just can't get past the fact that the record center hole accuracy produces a Wow&Flutter in the 0.5% range. Without a self centering tt/platter design, that number cannot be bested. |
Richardkrebs,
very informative, thanks for taking the time to post.
I have learned first hand that specific tables I have either owned and/or have listened to don't meet even your number 1), not sure about the other two.
I do like what you wrote that tables need to;
1) have absolute speed stability under all load conditions.
2) have absolute dimensional stability between platter and arm support.
3) be absolutely still, with total immunity from external movement.
Can you or anyone else please provide a list of tables that actually meet and pass these requirements |
Richard mentions the issue of 'Stylus Drag' which many think is an exaggerated myth? On Timeline's own YouTube video.......using a Transrotor belt-drive turntable with a heavy platter (and high inertia).......notice at the end, how after the speed has been corrected according to the Timeline......when the tonearm drops on the record, the speed immediately slows HEREWith the Victor TT-101 DD turntable however.......notice the complete lack of 'stylus drag' even with two or three tonearms in operation HEREPlease forgive the amateurish video technique as I held my iPhone whilst talking and 'acting' :-( |
Dover, with my Salvation, correct speed is normally reached within 3 seconds, as opposed to the 10 seconds plus my belt drive did. And additionally, it takes a LOT of manual pressure to slow the platter down in the Salvation, a lot more than my belt Orbe. I'll take that as a high torque system. Certainly higher than any of the more expensive belt drives I auditioned. But I'm sure it's not quite in SP10 Mk2/3 territory. |
Dover
Yes we are measuring an error and correcting it before it gets worse.
This is the old argument about feedback correcting an error that has already passed. The nature of this feedback and the torque/ platter moment are critical here. The motor must totally dominate the platters rotation. We are only asking the motor to correct a tiny change in speed. With sufficient torque and the correct feedback curve this is not an impossible ask.
I agree it has to go some way wrong for it to sense and thus correct. What we are preventing here is it getting any worse. Further, as I said the motor self corrects as well. This action being independent of the servo.
You said in one of your posts that you needed to correct for stylus drag when you tested with the timeline. Obviously the drag is not constant so we are ( in an open loop system) relying on inertia to save the day. The question is. Is this high inertia enough? (I wonder how quickly you observed the speed change after lowering the stylus)
Lets say in an extreme example we had a sustained high amplitude low frequency organ note lasting say 20 seconds followed by a flute playing very softly.
The platters inertia even a massive one would not be sufficient to maintain the correct speed during the organ note. Thus the motor would slip back in phase slightly to compensate for the higher torque demand. When the flute comes along the torque requirement would reduce. If the motor has high torque capability there is a risk of temporary over speed.
So the question of always needing a high inertia platter is better answered that the motor torque, platter inertia need to be matched to optimize speed stability. A platter of say 20kg has 8 times the moment of a 2.5 kg platter as fitted to the Goldmund I tested, assuming they have the same radius of gyration. The correction current I observed would indicate that a 8 fold increase in moment would not be sufficient to push through the drag modulation. Note high frequency correction was evident
BTW I was not arguing the superiority of DD over other drives. I was stating that stylus drag is real and significant and to improve the resultant speed errors, closed loop speed control is indicated irrespective of the drive employed or for that matter the platters inertia. It just happened to be a DD where I observed stylus drag in action. It is everyone's personal choice coupled with their biases when choosing a drive method and if open or closed loop. As I said earlier there are many paths to enlightenment and this should be celebrated. My opinion is simply that. My opinion no more valid than anyone else.
Clogging of course this is present in all drives employed
It is up to the listener to decide which is less intrusive
Clogging at approximately 11 hertz with the DD example you gave or clogging at approximately 120 hertz with the BD example,while acknowledging the lower amplitude of the BD.
As to the perceived superiority of the MK3 over the MK2
I can only assume that the engineers learnt something in the intervening period between the two designs. So probably all of the above. Further the general engineering in the 3 is superior. This has to have some bearing on the performance. |
Jazdoc
I agree totally with you. There are many other important parameters that must be addressed in a TT design
To state the obvious. A complete TT assembly including arm and cart is a machine that measures tiny movement with respect to time.
Over the years I have built maybe 10 TTs from the ground up, BD and DD. plus a few arms.
The conclusions drawn from this experience which parallels much written in the various forums here is this. If we are seeking the unatainable goal of perfection a TT must..,,
1) have absolute speed stability under all load conditions.
2) have absolute dimensional stability between platter and arm support.
3) be absolutely still, with total immunity from external movement.
Obviously there are other considerations, but these seem to be the core requirements
For example we would fail requirement 2) if there was any bearing noise, as this would cause dimensional instability since it would be moving the platter about.
Ct0517 the TT under test was a Goldmund studio with a Syrinx PU3 arm and I think a Monster 2000 MC cartridge.
I agree it was an astonishing finding which clearly demonstrated the effect of stylus drag. I hasten to add that I am in no way criticizing the Goldmund. It was simply correctly doing what it was designed to do. From memory it had a 2.5 kg platter with lead weights around its circumference. Thus for its weight, the platter had a relatively high moment of inertia.
The conclusion drawn from this test however would indicate that some form of real time speed monitoring and correction regardless of drive method, should be employed if we are to satisfy condition 1)
It is up to the listener to decide if this level of speed stability is necessary and can be engineered in such a way as to be benign.
For me the answer is yes and yes. |
Richardkrebs - Interesting post. Could you please elaborate on a couple of points. Contrary to some opinions expressed in these forums, the servo does not intervene unless an external load causes a speed change. ( this assumes that the TT has been put together as the designer intended). the motor does slip back in phase due to stylus drag...This can be seen by scoping its power supply. And watching the current draw. It was actually possible to recognize the music being played at the time on the scope. The speed sensor was measuring these tiny errors and correcting. This could be observed by watching the motor draw current in sync with the music. An amazing observation. The conclusion is that some form of speed correction is required if we are to seek good dynamic speed stability. So as I read it Para 1 - The servo only cuts in when speed changes Para 2 - Motor slip is occurring as a result of varying stylus drag to a degree that you can follow the music by scoping the current draw Para 3 - Your conclusion is speed correction is required for dynamic speed stability based on your observations. These seem contradictory. Are you saying that most direct drives dont speed correct all the time, but that they should be correcting more frequently for variable stylus drag ? Isn't speed correction for stylus drag shutting the door after the horse has bolted ? If the current draw is up AND down with the music, when do you propose to correct the speed UP and DOWN before, during or after the event ? Doesn't this just suggest that for whatever drive system/platter/arm/cartridge you have it must have enough energy storage or overkill in terms of motor drive & inertia to ensure the variable stylus drag does not impact speed at a micro level. Are you not presenting a strong argument that all TT's should have a very high mass platter ? ( unless of course you can scan the grooves and preprogram the required changes to the motor controller to preserve micro dynamics ). The other question I have for you is torque ripple, or cogging. As I understand it the torque ripple or cogging torque will vary because a Direct Drive motor is running much slower than a small pulley/platter. For example DD - 33.33rpm x 20 poles = 20 poles per revolution of record. AC/belt - 1800rpm x 4 poles = 216 poles per revolution of record. Disclaimer here - I know you also have to factor in the number of slots, which could increase or reduce the differential in this example, but doesn't eliminate it. Cogging torque results in torque as well as speed ripple; however, at high speed the motor moment of inertia filters out the effect of cogging torque. Presumably a high mass platter, provided it is direct coupled to the pulley with an inelastic belt, can assist in smoothing out any torque ripple if it exists in both instances. Can you explain why I can hear such a big difference in speed stability between the Technics SP10mk2 and SP10mk3 ? Do you think it is the higher torque, superior motor controller, higher mass platter of the mk3 or all of the above ? Cheers, Dover |
Tony,
The issue I see with test record frequency measurements is that on the test record, groove anomalies and the good possibility that the test record center hole is not exactly center can throw off the measurements. Prior to using the laser reader I used a 1000 hz test tone on a record and used a Fluke digital multi-meter to measure the output frequency. It would oscillate + or - 1 hz measuring the frequency at 1000 hz...With the laser, my table is stable at 33.00x rpm, where x fluctuates up to .008 every few rotations. I think that is quite good for a belt drive. I am going to try the platterspeed app for iPod to see how it compares and I am especially interested in the time plot. |
...unlike my clunky grammar which required zero thought. :D |
Dover, your post leaves me with a lot of questions, but I won't go there. However, there is a need to explore torque and inertia. They can be confusing terms. Explained in the very most simplistic way possible, torque is what you need to get the platter spinning, and inertia is what you need to keep it going smoothly.
So, it is possible to get very good results with a very low torque motor because you can still have good inertia. The downside is that the turntable will reach its speed much more slowly, assuming the platter is a heavy one.
You can have both high torque and high inertia, but there is usually a price to pay. That price is motor size and lots of heat generated by it. Ashland was noted for making such motors, and quiet ones at that. The one used in a Fairchild 750 studio machine is the size of a clothes dryer motor, and it runs very, very warm. So does the more common one found on some Rek-O-Kut turntables and the Canadian made McCurdy. I would be happy with either motor in the Saskia, but they are no longer available.
By comparison, we are stuck with lower torque motors, if we want great precision, but we can still have lots of inertia. This is where system design comes into play, and done right a design can greatly benefit speed accuracy.
I suppose the point here is that most turntables, if not all, are compromised to some degree, however small. The trick is in making certain that any of those compromises do not negatively affect the end result. Hopefully, reliability and looks aren't affected, either. It isn't as easy to accomplish as you might think. Such an undertaking requires a lot of thought.
. |
Spirit of music
Where are the specifications that suggest the Transfi has high torque.
On the contrary, from their website -
"Note1: The 9kg platter has immense inertia & will take a few seconds to respond to the control knob. Only very slight tweaks are needed.
Note2: You will find speed drift may require frequent minor adjustments until the bearing, motor & electronics are burned in.
Typically, starting from cold the system will run slightly fast. As operating temperature is reached it will slow. A suggested method of operation is to let the system warm up then set the speed. Play several records & fine tune until the speed remains constant.....then leave the control alone.
When you switch the system off, the motor does not need to be disengaged from the traction belt. The next time you start the system from cold, it will run fast. If you try to adjust the speed at this stage it will slow as the system warms, so best to let it run fast until it settles to the correct speed.
IMPORTANT
The whole system of speed control is finely tuned, & any variation in consistency may require adjustment, from VTF of the cartridge to the weight of record clamp used. Sophisticated motor speed control methods have been ditched in the case of Salvation as these all proved detrimental to the sound using this direct rim drive method. In practice, speed drift on Salvation is not an issue providing you are not varying the way you play your records from record to record or are a stickler for speed accuracy! Please consider this before ordering."
If you have a temperature controlled room, the angle of your dangle is stable, and you are not a stickler for speed accuracy, then this is the turntable for you - this is their own words.
The Michell Gyrodeck is not a paragon of TT speed accuracy that should be used as a standard either - tiny motor, stretchy flimsy elastic belt, floppy suspension and all.
|
My thoughts on my direct rim drive is that it's torque is of a magnitude greater than comparable belt drives which rely on platter mass and momentum to maintain speed.
The Salvation's high torque smooths out the speed inconsistency I became more and more aware of with my belt Orbe. This enables the Salvation to deal with groove modulation effects much better than my Orbe.
It's been a total revelation to hear piano notes solid as a rock when struck and as the note decays. My Orbe never quite managed this trick.
I'm convinced eliminating groove modulation timing variability eliminates a whole series of artificial warmth artifacts, and allows a real cognitive ease when listening to vinyl.
But Pete, I'm sure you're correct other factors eg isolation etc. contribute to the overall sound. However my paradigm shift moving from belt drive has convinced me that high torque average speed stability and instantaneous resistance to groove modulation is critical. |
Yes, and the closer the dot on the wall or paper is to the Timeline pointof origin, the harder it will be to for the eye to detect any drift. So if it looks fine at 18" it may be apparent at 10 feet over time that the speed is off.
I agree with Jazdoc's observation that as long as one is very close to accurate speed other issues are very important. IE, How the turntable deals with vibrational energy generated from the motor, the bearing, airborn, floorborn, the stylus/groove interface, the armboard etc. It is not clear to me that absolutely perfect speed accuracy and consistency is the most important characteristic of a turntable. |
I have an FFT analyzer app on my iPhone. I used a B&K calibrated 1000Hz test tone and the FFT plot was dead on. It is about the frequency counter tied to the internal clock. I don't know the accuracy, but I figure it must be within the range of the timeline- quartz crystal clocks inside their processors. |
The original Timeline flashes once every 1.8 seconds (1 revolution). The latest version, which is at least about a year old, flashes eight times every 1.8 seconds.
Tonywinsc,
I don't know how much faith I have in the accuracy of an iphone microphone! |
An accuracy of 1/1000 rpm is 0.003%. This is only as good as most high end tt's. It needs to be an order of magnitude better than that. It will be good for dialing in speed, but not for examining Wow&Flutter. If it is off 0.003%, then the platter will gain/loose 1/3 of rotation per 10,000; assuming all else is constant. I'd call that good. Why doesn't anyone talk about the iPhone app? It at least plots speed over time for you. |
I am now using laser tach to determine my platter speed and stability. IMO, it is the most accurate way to gauge the speed on the platter. Accurate to 1/1000 th of a rpm. Only $200.00. It should be placed on a tripod for the most accurate measurement. Monarch PLT 200.
http://www.omnicontrols.com/detail.aspx?ID=3720 |
Mosin/Richardkrebs – thank you for your excellent thoughts on this thread. Mosin – as just an amateur hobbyist myself, most of what you have said is in sync with what I have heard with my TT’s the last few years. I agree that string drive could be a little fiddly, when trying to convert a belt design TT to thread/string. But I have found that on a string designed TT – once the string technique is learned (there was a learning curve with mine), it was pretty much plug and play after that for me. RichardKrebs It was actually possible to recognize the music being played at the time on the scope. The speed sensor was measuring these tiny errors and correcting. This could be observed by watching the motor draw current in sync with the music. An amazing observation. I find this simply incredible. Are you able to tell us what turntables / tonearms /cartridges you used during this analysis/testing? |
Palasr, I am fairly certain the Timeline flashes more than once per revolution. (I cannot recall the exact frequency; maybe Mosin knows.) Thus it may detect short term speed instability, in fact, altho with what accuracy I cannot know unless I know the frequency.
You would think that the KAB strobe could also hint at short term speed instability, as the "33" would waver or even flicker back and forth while under observation. But I don't know how sensitive it would be to such aberrations. |
Just to clarify for those not familiar with the device, the Timeline flashes a dot on the wall once per revolution; it is not a continuously illuminated reference point and hence cannot show aberrations occurring in one revolution, but only deviation from a fixed reference point (on the wall for example) over some period greater than one revolution. Jazdoc's point is well taken. |
Interesting how the general question regarding drive implementation has quickly narrowed to a focus on speed stability per single revolution. I suspect that this is because this is one of the most easily measured paramters. It is human nature that people respond to what is being measured and audio is no different. However, this can have untoward consequences. I am old enough to remember when THD was touted as the ultimate measure of amplifier quality but improvements were acheived with increasing negative feedback; ultimately with deleterious effects on the end product.
Single revolution speed stability is clearly important, but, perhaps, this is not the only (or even most) important consideration. As others have alluded, the Timeline only measures accuracy per revolution, not speed changes within a revolution. Theorectically, if the first half of the revolution was 16 2/3 rpm and the second half of the revolution was 50 rpm, the Timeline would be spot on at 33 /13 rpm. I doubt that anyone would consider this a quality turntable.
I supect that the amount of internally generated noise and vibration and ability to dissipate borth internally generated and external noise and vibration are also important to the overall quality of any turntable.
At a certain level of performance, are other parameters more important to vinyl playback performance, i.e. tonearm and cartridge quality?
For the record, I'm not a turntable designer and own a belt drive turntable but would be comfortable owning any number of idler wheel and direct drive tables. |
Richard, That was a great post. Very informative. Answers a question I have been privately asking myself: Several of the latter day DD turntables, and I believe one or two of the new rim drives, tout the lack of a servo mechanism as a selling point. You can guess the rest...
However, those of us who have been around here for a while have in fact addressed the question of instantaneous speed variation that could go undetected by any measure of "average" speed. Whether the Timeline is any better than the KAB strobe (the best of all strobes, IMO) at detecting such short term errors, I do not know.
Mosin is too smart to post any lists here, and who could blame him for not doing so? |
Peterayer,
A distance for sure is important, I have been doing this very easily for a while now and if the table isn't close to a wall I just use 2 light rulers and tape them to the back of the table stand along with a pce of paper between the two with a pce of painters and a dark line on such so it's very easy to view between so it's under 2 ft
All the tables I have tested, no worry about waiting for 20 minutes either. Most failed within a few rotations even after using the TimeLine to actually try and set the speed accuratly. I found most tables were not capable to be set for accurate speed.
Using the strob, numerous tables that were used and then rechecked with the TimeLine proved the TimeLine is a more accurate devise and all these tables failed within 10 or so rotations either too slow or too fast and that was with no stylus even on the record.
This has really left me scratching my head. |
I made an error in my last post. The Timeline is accurate to one part in two million. |
The timeline has a quartz clock. It is accurate, according to Ron Sutherland, of two parts per million. That's very good, and I have no reason to doubt him.
I don't know the limits for other drive types, but it is theoretically possible for an idler to be accurate to around one part per million, so my controller was designed for that. You could go further with a GPS referenced OCXO clock in the controller, but could anyone hear it, and could the device keep up with the clock?
At some point we have to question the merit of it all because there are mechanical limits. And, just because a turntable has a great clock doesn't mean the turntable spins accurately, and just because it spins perfectly in the lab doesn't mean it will do it under every condition, in every environment. Still, I believe it is the responsibility of a manufacturer to get as close to perfect as he can given the price point of the machine he is selling. If you pay small money, you aren't going to get super accuracy, but you may get a very musical turntable that is consistent. To me, that's worth a great deal, although I personally try to push the limit to its threshold. Essentially, you should get what you paid for.
. |
Gentlepeople
I have not used the timeline but understand that if a TT was to say AVERAGE 33 1/3 rpm over a LP side, it would pass the timeline test. Am I correct in my assumption?
If so we can easily discount any TTs that are not averaging the correct speed. But this test does not take into account dynamic speed changes.
With most DD TT's using a DC motor, a controller produces a rotating field at the desired speed. The magnetic poles are pulled around at this speed. Contrary to some opinions expressed in these forums, the servo does not intervene unless an external load causes a speed change. ( this assumes that the TT has been put together as the designer intended). If the load does change, the magnetic poles will move back in phase slightly until output torque matches the new higher load. The magnetic poles will still be following the rotating field so it will be again rotating at the correct speed. But while this is happening the motor tends to self correct as its torque increases with the phase shift between the rotating field and the magnetic poles. AC motors exhibit the same self correcting characteristic. For a DD TT to fail this average test it would have to be incorrectly designed.
A good string drive with zero slip and idler drive would I imagine also pass this average speed test.The only way for these to fail would be for the motor to be under such high load that it jumps a pole. No normal retardation torque would be sufficient to cause this.
But here is the tough one, the motor does slip back in phase due to stylus drag without jumping a pole.Even at treble frequencies with one DD TT I have tested. This can be seen by scoping its power supply. And watching the current draw. It was actually possible to recognize the music being played at the time on the scope. The speed sensor was measuring these tiny errors and correcting. This could be observed by watching the motor draw current in sync with the music. An amazing observation.
The conclusion is that some form of speed correction is required if we are to seek good dynamic speed stability. High moment of inertia platters will of course help but only for momentary load changes. Sustained increases in load will cause the same phase shift. If no speed correction is employed, we are relying on the motor self correction characteristic. This may be enough but note the motor needs to move back in phase, I.e momentarily slow down before the automatic increase in torque output comes into play. As with all things engineered, compromises are a sad fact. We each need to decide what compromise best meets our biases.
Some of you may have been asked the thought experiment at college where a tennis ball was thrown directly at the front of an oncoming train.
The train in theory slows down. |
For a Timeline test to be truly useful, some standard should be applied. For example, I saw a DD table tested with the Timeline. The owner held a piece of paper behind the turntable and demonstrated that the red dot did not drift during the 20 second test. I asked him what would happen if he let the dot fall on the wall about 4-5 feet away and waited five minutes. He admitted that a further distance would show a drifting over time. A video with a set distance of the laser dot to a wall, say 5 feet away during a period of ten minutes, or with the stylus at the beginning, middle and end of an LP would be good, but I don't want to have to watch a 20 minute video showing the entire length of the LP. Perhaps a fast forward feature with a time stamp and mark on the wall for some kind of consistency would work. Also the test should start with the stylus not contacting the LP and then during the test, it should be lowered onto the LP.
I agree that the results would be interesting, though I really wonder if the speed variation of a successful KAB strobe result versus an unsuccessful Timeline result would be audible. My table shows a steady result with the KAB and I have not had the opportunity to borrow a Timeline.
I would think that any manufacturer who has a design which passes a Timeline test would want to show such a video for marketing purposes. This issue came up in another thread about speed accuracy and someone asked about the accuracy of the Timeline device itself. If the strobe is slightly off, but the table is accurate, the red dot would also drift slightly. Measurements are only as accurate as the measuring devices themselves. |
Spirit, Have you tested the Salvation TT speed stability with Timeline?
I agree with SYSKOS, that Timeline results of members' various TTs would be a very useful grade scale (pass or fail). |
Well, I'm going to put my vote in for the Trans Fi Audio Salvation direct rim drive tt (with Terminator T3Pro linear tracking tonearm).
I'd been running a belt drive Michell Orbe/SME V for 10 years, and investigation of uber pricey belt drives like the SME 20/30, TW Acustic AC3, Brinkmann La Grange /Balance etc showed an incremental improvement, but not enough to go with the upgrade. And, this in tts costing $20000-$40000.
But I then came across the Salvation, and wow!
I'm NEVER likely to go back to belt. I'm getting a unique combination of the best of analogue ie bloom and tonality, with an almost digital-like accuracy and neutrality.
It's unlike anything else I've heard when playing vinyl.
Getting away from belt related speed drift really produces a fantastic unwavering solidity to music, most noticeable on rock solid piano notes, even as they decay away in the soundstage, and no audible wow and flutter as lp side end approaches. Previously I would always be aware of fluctuations as piano played, especially individual notes, but not anymore, and often I'll be suprised that I haven't picked up on side end groove modulation as the stylus plays the last few seconds of the end of sides.
I've run a thread on the tt/arm giving a more in depth appraisal of my experience. |
Mosin,
please list ones that actually pass, this will be a starting point |
I have checked a few, but mostly I have checked motors that are commonly used. I was surprised. |
Mosin, A lot of new ones pass, but the surprise is which ones. This sounds like you could already produce a list for us? :-) |
Halcro,
Yep, but that won't happen. A lot of new ones pass, but the surprise is which ones.
Some old ones don't pass, however. I built a DIY turntable around eight years ago that started life as a Lenco. It runs a little less than 1/4 RPM too fast no matter what I do, so after a frustrating hour wasted I quit tinkering with it. I could never get the wheel placed accurately enough to correct the issue, as minor as it may be. It's dead on according to the KAB Speedstrobe, so I suppose it is close enough. Maybe I'll revisit it someday.
The real problem is with those turntables out there that do not keep a consistent speed. It is one thing to have an ever so slight speed issue that is evenly paced, but quite another when it varies, especially if it varies abruptly.
. |
Wouldn't it be interesting if the only tables to pass the 'Timeline' test were all 30 years old? |
Sksos1,
I think we all know which one you will put at the top of that list!
Seriously, such a list would be surprising to a lot of people, and it would undoubtedly generate angst among many manufacturers, not to mention all the explanations from end users claiming the results are from someone with an axe to grind, or it was just some unlucky random sample. Whatever, the thread would probably become Flame City right away.
. |
So let's start a thread with which tables have and which do not have accuracy using the Timeline device? |
The main problem of idler drive is people have opinions on it after hearing turntable from the 60'. I have built my lenco after reading Salvatore review of the J Nantais reference Lenco.
I have tried different material and finished with a non wood plinth, a reference bearing ,and some tweaks ,an OL conqueror mk II and a zyx airy 3 . The sound is impressive, nothing to hear here with the traditional sound of idler drive.
Then i have heard a Lenco made by a hifi fanatic, and very sympathic person. He built a 200 kgs Lenco with its own table (as the goldmund reference),the finish is impressive, there are many many tweaks but it's idler drive and the sound on his high end system is incredible, in the treble it betters all the belt drive turntables I have listened to. |
