Henry,
you made a good point with the Timeline & the Nakamichi. The red signal keeps stable even when the needle runs down on the record. Ths is an advantage of the DD design (and I have to correct myself - no manual speed correction is necessary on all my TTs).
Tonywinsc,
if we start a competion by using a stopwatch I might win with the EMT ;-)
Frogman,
you are right, precision control is the one thing but musicality and a sonic footprint is the other one. Therefore I find it hard always following the neutrality apostles in our community - but there are not so many in this thread. Am I right?
best @ fun only |
Thanks, Tony, for introducing some science to the foregoing discussion. I know I am going to sound like one of Syntax's "fanboys", but I have been listening to my Technics SP10 Mk3 for the first time in extensive sessions over this past weekend. And I am astounded by the rhythm and drive this table can impart to music on LPs with which I am very familiar. Try "Art Pepper + Eleven", which contains just about every bebop rhythm one can imagine. There were tears in my eyes, literally. Yes, Tony, the Mk3 can bring its 21-lb platter up to speed in one rotation, probably sooner. I have been arguing this stuff on a theoretical basis; now I am a true believer. |
Thuchan, I reluctantly admit to being a "neutrality apostle". But I am reluctant only because, IMO, the term neutrality is usually misunderstood. In your comment you pair the term neutrality with sonic-footprint. From my vantage point, sonic footprint is, by definition, usually the result of distortions. Neutrality (or however close a component gets to it) is a measure of musicality. In other words, a component that is truly musical IS closer to neutral. "Precision control" allows musicality.
Regards. |
well said Frogman, but I am not pairing sonic footprint and neutrality. Sonic Footprint in my understanding is that you recognise the turntable's abiliy in producing fine music. Just take the EMT R80 (927) as an example. Agree completly that Precision Control allows musicality. I for myself need both!
Some people argue that a turntable should just reproduce which is a funny statement. A Linn Lp 12 and some of the smaller new Thorens tables e.g. also reproduce - but with what kind of result. Of course some people may like it. good. Distortion is a wide field and I know someone in this community who loves the term.
In my understanding sonic footprint is not the result of distortions at all. The Nakamichi, or the EMT as well as the Micros do have a sonic footprint which is different. Does this mean I am surrounded by distortions, God beware. I would jump from the bridge...
best @ fun only |
Dear Thuchan, Please do not jump, but isn't the answer to your question obvious? If the 3 tt's sound different, then they are introducing different "colorations". Or possibly one is "neutral" and the other two are introducing colorations. No matter how you say it, these colorations amount to distortion in one form or another. I would also say that it does not matter, as long as any of them can make you feel you are at a live event, or even if they make you feel alive. How about the Continuum, which you don't mention? |
Halcro, as I posted on 11/16 the SP-10 Mk2 manual states that table will maintain correct speed if up to 500 arms could be lowered simultaneously while tracking at 2 g. Even with an error range of 10%, it should be correct with up to 450 arms! From that, your three arm test was not much of a challenge. ;-)
However I suppose the problem with the Technics statement is the table could "maintain correct speed" with up to 1K gram weight applied. That could be different from not maintaining speed at the moment the weight was applied. In other words, should one allow say one revolution to correct the speed with this weight? That would be a big difference in sonic terms.
So if I'm understanding this, your laser mark should be measured precisely at the moment each stylus is lowered onto the record with no time interval to allow your table to correct for the added drag. |
I found an article online about the Nak. Very interesting tt. The author had an excerpt from an interview with the designer. He substantiates my point exactly. He says vinyl record runout is the elephant in the room that tt designers ignore. As for inertia: Torque= J*omega, which is the angular term for F=ma. The tt motor provides the torque and the platter bearing and stylus apply a counter torque. The inertia of the platter determines the rate of change in speed (deceleration). Say for example the motor is uncoupled from the platter. The platter is spinning at 33.33 rpm. (ignore bearing friction for a moment) Now drop the stylus onto the record. A 20 kg platter is going to decelerate at a lower rate, for example, than a 2 kg platter.
Now let's hook the motor back up to our platter. The motor is either clocked to the 60Hz line frequency or is feedback servo controlled. So it holds the platter at 33.33 rpm. Any perturbation in the platter speed causes the torque output of the motor to change in order to restore 33.33 rpm. The motor could do it's job regardless of the amount of inertia in the platter. The stability of the platter speed is based on the control loop and torque of the motor combined with the system inertia. That means the designer has to couple a motor and platter as a system. The platter is designed to be a mass damper. We use mass dampers in dynamic systems. We use mass to tune System Natural Frequencies and keep them out of certain operating ranges. A bigger platter requires a higher torque motor in order to be stable. Perhaps the youtube example is a tt design with an undersized motor. I would say as a rule of thumb, the motor in a tt should be able to accelerate the platter up to speed within one rotation. To me that would indicate that the motor has sufficient torque to maintain a stable speed. btw- I just checked my tt and it is up to speed within one rotation. |
Correct speed with 500 arms? That is not a helpful statement since we don't know what the definition of "correct speed" is. What matters is to reduce the effect of a single stylus to below audibility. I don't think that anyone has been able to quantify what that specification is. But there is ample evidence that extremely small speed perturbations are audible.
It is is misnomer to assume that a massive platter fixes the stylus drag issue. A heavy platter results in a smaller perturbation spread over a longer period of time. A light platter will slow more but will recover more quickly. A heavy platter changes the problem but does nothing to eliminate it. I think that most people prefer the shallow but longer perturbation from a heavy platter, but ultimately it's a matter of taste, not superior stability. |
Dear Lewm,
ok didn't jump so far. Maybe I have a different / not typical understanding of footprint or better let's say character or personality of a turntable.
I know some audio gurus carry the philosophy of neutrality around the world, which should mean, the more neutral a turntable is the better for the reproduction. In their sense it is absolutely necessary that a turntable should not become musical - but neutral. A neutral turnable cannot be musical, warm or dynamical, or lively. It is and has to be just neutral. Everything else is coloration or distortion. Am I right? Okay. In this understanding I am happy to live with coloration & distortion - and I don't need to jump.
best @ fun only |
"Mosin, as inertia is directly related to mass and friction.....are you saying that heavy platters have inherently greater inertia than light ones?"
What I'm saying is that sheer mass is less effective when it is capriciously used than when it is purposefully assigned to achieve an optimum moment of inertia. As far as mass on a platter, I feel that its benefit as an isolation component is another key reason to use it.
Of course, there are more ways than one to skin the proverbial cat, so lighter platters may also work with some designs. I work solely in the arena of idler drives, so that is where I spend my time looking at such things. Recipes vary, but the performance depends on the entity as a whole, and not just a single part because every part is critical to the outcome. Any shortcut is a compromise. At least, that's what I have come to believe. |
I am with you in this dilemma, which is why I hate the word "neutral" when used to describe an audio product. It can have any meaning that the user wishes it to have. One meaningful way to use it would be to say that "I have heard this or that LP many times in my own system using a wide variety of turntables, tonearms, and cartridges, and I find that this turntable/tonearm/cartridge seems to add less (or more) to the basic sound on this LP than does that turntable/tonearm/cartridge". Or something like that. |
Excellent video production Henry ! Your accent doesn't come through in the posts here. :^)
My American and UK co-workers tell me Canadians have strong accents too but I don't believe them - eh ?
I think this Utube stuff opens opportunities here for everyone and the gear.
Would love to see more of you out there with your wonderful gear.
Thuchan - how about a video demonstrating your favourite audio toy you could speak Japanese too.
Wonder what Raul sounds like?
How about a 3 minute utube video Raul demonstrating your tonearm features to us ?
Technology awaits. All in fun
Frogman - I agree with you.
Tony great info
Cheers Chris |
Tony, I don't quite see your "one revolution" hypothesis. The platter once in play never comes to a complete halt. I think the point is that the motor needs to have "enough" torque to keep speed stable. And the definition of "enough torque" is related to inertial mass of the platter and servo design. In bd turntables, the belt/thread/tape is an added factor in the equation. In idlers it's the idler drive system. |
Your accent doesn't come through in the posts here. Accent??........I have an accent??! |
Henry , I think he meant your English dialect |
The mass of the platter has nothing to do with speed control other than it is the "m" in the equation, F=ma or T=J(Omega). The motor controls the speed. Its that simple. As shown by the equation, more mass means the motor must generate more torque to provide the same acceleration. How much acceleration is enough? Well, it depends on how well the designer wants to hold the exact rotational speed under dynamic conditions. I stated as a rule of thumb based on my knowledge and experience designing dynamic systems, (not turntables) that a tt motor should be able to accelerate the platter from 0 rev/s to 0.5556 rev/s within the first rotation. Some motors may be able to do better than that, but if it takes a motor more than one rotation to get the platter up to speed, then I think it might lack sufficient torque to maintain a stable speed. I could be wrong here, I've never designed a tt myself. But to carry it further, the motor is designed to spin at a certain speed. That control system for the motor can be as simple as being clocked to the 60Hz sine wave of the AC power to a very sophisticated electronic servo feedback control system. However it is done, the resolution and rate of response of this control system results in the level of stability of the platter speed. The system design dictates how much speed error can occur before it corrects it and how fast it can correct the speed. At this point I could get into the impact of an underdamped or over damped system, but the point is the tt designer must come up with a system that includes the motor torque, speed, resolution of the control loop, platter inertia.
I might be wrong here, but I have observed that DD turntables tend to have lower mass platters versus later BD tables. I'm guessing that the torque available from DD motors is less than for BD considering BD motors get a mechanical advantage from the pulleys. Higher mass platters offer a nice stable sink for the vinyl record to minimize vibrations. The added inertia of high mass platters is probably more of a problem for tt designers in terms of speed control- just because it requires more torque from the motor.
I'm starting to think the rhythm and pace might be linked more to the tonearm and stylus. The runout of the vinyl record, as I showed before, has more impact on Wow than does the tt. But the swaying of the tonearm, which is part of the Wow problem must also influence the tempo of the music I think. Couldn't the side to side movement of the stylus in the groove alter the tempo? Is that what tonearm damping is all about? I don't have damping. Does anyone have experience that says tonearm damping improves the tempo of the music? |
Halcro - great demo, no accent.
I agree with Lewm on neutrality, different for different folks. We all know if we have a preamp with a dip at 3k say and we listen to it for a long enough, the ear/brain adjusts, and when you try something else that is neutral you think it has a peak at 3k.
I would suggest that speed and timing are far more important, as once you have lost the timing you cant recreate it in your head.
Re Wave Kinteics NVS that started this thread - did anyone notice that that original thread has disappeared. Do manufacturers get bad press/comments pulled from the forum ?? |
Ha Ha Ha - yes sure dialect. Its wonderful either way Henry :^)
And music is the common language here.
ACCENT vs DIALECT
NEUTRALITY vs COLORATIONS
What a great hobby |
Dear Halcro: I could listen to you reading the phone book and find it gripping. You speak with a deliberateness and cadence of several philosophy professors I know. Put differently, you're the John Gielgud of the audio world.
More videos! |
Dear Thuchan: I think you have a wrong concept of neutrality/accuracy on audio devices.
IMHO any audio device should let pass the LP/cartridge signal " untouched " and this means with accuracy/neutrality: IF THINGS ARE THAT THE THE TRACKS ON THAT LP ARE WARM/COLD/LIVELY/DYNAMICS/BRIGHT/DULL/DARK/ AND THE LIKE WHAT SUPPOSE THAT ANY AUDIO DEVICE/AUDIO LINK IN THE WHOLE AUDIO SYSTEM CHAIN MUST DO IS TO PASS ALL THOSE LP MUSIC RECORDED CHARACTERISTICS WITH NO ADDED DISTORTIONS/COLORATIONS BUT WITH ACCURACY/NEUTRALITY.
ALL THOSE MUSIC RECORDED CHARACTERISTICS came/comes in the LP and in theory are not part or be/bee need development by the audio links: what you hear must be what is in the recording: adding NOTHING!!!!! or do you think that your system is so good that can improve what comes in the recording?, no way my friend no system can do it!
Do you think that all those additional " stuff " in your Micro Seiki improves the sound?, NO only change and add different distortions with no real improvement.
Regards and enjoy the music,
R. |
Tony, What I meant was that in direct-drive turntables, the motor, the drive system (aka servo), and the platter together form a closed system. So indeed the mass of the platter has everything to do with it. If you don't see what I mean, try removing the platter from a direct-drive turntable. The result will be a pronounced herky-jerky motion as the servo goes searching for its proper load. If you dramatically increase the mass of the platter (yes, "m"), the servo can get similarly screwy, slow to correct for off-speed moments, but it is less easy to see. It is the servo that tells the motor "how much acceleration is enough" to get back to equilibrium.
None of this is to contradict what you say about LPs with off-center holes (i.e., most of them). That's a big, important, and separate issue. |
Thanks Dover, Chris, Thuchan & Banquo,
I appreciate your encouragement :^)...... John Gielgud (blush).
Dover is from New Zealand.....so of course I sound like an orator to him:^)
I was going to follow up with a video of the Raven AC-3 under test.......but I don't think it's fair?
Everyone can test his own turntable once armed with the Timeline.
There will be some shocks? |
Tony,
The TT-101 does in fact reach its correct speed within a revolution as seen on the Timeline.
The actual specification states that 'starting time' is within 0.6sec.
Starting torque: 1.2Kg/cm
Speed deviation: 0.002%
Drift: 0.0004%
There appears to be some confusion about the functioning of the quartz locked positive and negative servo control of the TT-101?
It does not compensate for a speed deviation over a complete 'revolution' or series of 'revolutions'.
In other words......if there is a slowing down due to stylus drag........the servo does NOT speed up to 'compensate' for that 'lost' time and thus keep an 'average' continuum?
The servo does not know how many revolutions it is completing in any listening session....nor does it care.
It cares only about 'instantaneous' micro speed control.
What this means, is that if there were a slow-down due to stylus drag at any point of a record's playing cycle......that error would be permanently imprinted on the Timeline 'Blutak' marker on the wall. And any extra deviations would be accumulative so that the laser line of the Timeline would 'drift' further to the left with every revolution.
This you will appreciate if you ever use your own Timeline on your own turntable?
It truly puts into perspective the performance of the TT-101 which you have witnessed on the video? |
H Lewm, yes, you are correct. That is called cogging. I'm sure BD motors do it too if they are unloaded. You just can't see it with your eyes because they spin too fast. That is what I was saying before that designers use mass as a damper- mass damping. All motors have some level of cogging, or ripple. Even your car engine has it as each piston fires. The flywheel smoothes out those ripples just as the tt platter smoothes out the ripples from the motor. The typical tt specs showing Wow&Flutter below 0.03% shows how well these massive platters are doing their job. btw, the more poles that a motor has, the smaller the ripples. I notice some of these expensive tables have quite sophisticated motors. Caveat Emptor always applies, but I think you are getting what you pay for in some of these expensive motor designs. |
Tony you may find Dovers record player interesting ,surely a heavy weight contender for ultra sophisticated speed control.
Henry if my memory is correct I seam to think that I read somewhere TW Acustics stated their motor speed control was designed to perform like a vintage direct drive. |
Dear Tony, Cogging is indeed a problem with motors, but what I described would not be strictly due to cogging. Mostly it is due to the servo hunting when its feedback loop is screwed up by the lack of a platter mass or in the other extreme, too much platter mass. Cogging will always be there and is an inherent property of the motor; some are less prone to cogging than others. |
In a way we should think different, because speed stability is one side, sound quality has absolutely nothing to do with it and a turntable which creates "something" is also a total different animal (Raul is absolutely right on that topic).
When you want speed stability, a direct drive has advantages because it always is in connection with the used voltage, it always correct its speed during play (accelerate-hold-reduce-accelerate-hold-reduce and so on).
Direct drives are good for those who believe, that this has something to do with superior sound quality. A listened to some really good designs and I know, this has absolutely no influence. A direct drive TT can sound thin, lifeless and boring. Maybe there are exceptions ...
A belt drive TT Designer has to solve some problems, see Belt quality for example. Most aren't even able to solve this properly, then we can't expect that those are able to design a proper speed control. and this story goes on and on.
When someone is reading this and has no time to read the former 3 sites
- go for any suspended Basis turntable with Basis Controller or Walker Controller
or
- ask Sorasound for an Amazon turntable, they have a Battery power supply.
That one is good.
- or SME 20/30
Others produce "something" what someone likes or not. Discussions about "this" are endless because one prefers black, white, heavy, expensive, rare, PRaT, catholic or islamic soundstage and so on. These "problems" were all solved years ago, unfortunately engineering is no longer part of High End Analog. It is replaced with "I like it". Analog is a following of steps done right. |
Gosh, what is left to say or think after that?
I agree that direct-drive turntables can be highly "colored", in a bad way. I also completely disagree; speed stability is the sine qua non of a turntable, no matter the drive system. "Sound quality", if by that term you mean the degree to which the sound emanating from the speakers can be made to emulate "real life" does depend very much upon speed stability. From that comes rhythm. From rhythm comes verisimilitude, in part.
Sure, a tt with excellent speed stability can sound bad for other reasons.
Why is a battery power supply, per se, likely to be superior to all other approaches to power supply? |
We have pretty good reports from TW Acustic owners, who have changed the standard PSU with battery motor control unit from Raven Black Night. |
No variable ac line = no variation in motor control = better stability.
Problem for many dd turntables IMHO is the fact that the motor MUST control (by nature here ..) the platter very direct with minimum delay.
Thus the use of a heavy platter with high inertia is counterproductive to direct drive.
IMHO however, high mass platter made with some insight in energy transfer and damping have inevitable positive effect on analog reproduction.
A DD with high mass platter "looks" at a similar problem as a BD.
aBoth have a kind of "overhang" in their reaction between motor speed adjustment/correction and reaction by the platter. |
To resolve this problem some BD makers use optical feedback - to measure the platter speed and adjust the motor speed "in time". I think the new "Micro Seiki" spaceship is equipped with such a speed management system. |
Dear Thuchan: Please read this about " neutral ", this add more sense to what I posted and telling you that I'm not alone, btw your dear friend Syntax agree too:
++++ " Takeda San says, "I was always frustrated by modern cartridges -- including my own designs in the past -- because they always sounded clean and nice but failed to present a very important element of music. What was missing was the linearity of dynamics. Many cartridges can produce clean sound but the sound is only one element of music. They fail to present the flow of music. Listeners may not realize this if they are not familiar with music that requires a wide dynamic range and delicate gradations within it. Large orchestral works and certain piano recordings are typical examples. I also wanted my Standard to be tonally as neutral as possible. Many cartridges have some degree of coloration to make them sound appealing. I didn't want to do that with the Standard."
of course that you don't have to agree with the " neutral/accurate " subject as Takeda San said: ++ " have some degree of coloration to make them sound appealing. " ++, if you are on this side good for you because that's what you like it. Neutral/accurate is in the other side of " I like it ", neutral/accurate is the way " thigs " must be it does not matters if we like it or not.
IMHO, if you own a good audio system and you don't like neutral/accurate performances then that " good " system has one or several problems else where, or your ears or both.
Re-read Frogman's post and if you have time my post too and some Syntax ones on the subject on other threads.
Regards and enjoy the music,
R. |
Dear Raul,
I know about the theoretical discussions you are referring to and so many people in this business. Regarding practical issues when it comes to listening it is not about the turntable adding something or not! This is not my point. You may bring down a turntable to neutrality and it sounds shitty or let's say clinical cold.I have heard so many totally neutral turntables and the owners were proud of their sound. Fine. The real art in turntable building or let's say also in dealing with different concepts/drives and comparing those is based on the ability of the turntable to transport the signal in an uncoloured and undistorted way - which does not mean that all turntables doing this are equal or coming with the same sonic footprint (!).
When you ever had the chance listening to an EMT 927 or to a very good DD or to a brillant belt concept ( lets take the Continuum as an example ), and I am sure you can, you will agree that although they are playing music in a wonderful way, they offer some differences. From my point of view it is the biggest missjudgement to put these differences (dynamics, musicality, bass grounding etc.) only to artifical add ons which should not be there.
Some people don't like the sound of idler wheels.I believe it is good listening to a well adjusted idler wheel. I have experienced the differences also of various prominent brands and models, good sounding and not good sounding idler wheels. An idler wheel can be very dynamically. Is this generally coloration or distortion in your definition? Or are you referring to not well adjusted tables - which is different.
If for example a SME is an absolutely neutral turntable in your or other people' s experience and you regard the sound it makes as a benchmark "in your undistorted world" perfect! For me it is not benchmark! But this is up to the preferences one has. I am sure we both must and will live with our different way of approaching practical listening experiences. What I am saying is: Too much in this forum is only and more or less theroretical based. Maybe we can bring some colour into it :-)
best @ fun only
best @ fun only |
Dear Syntax,
you are saying speed stability has nothing to do with sound quality. How do you mean this? If the speed is varying enormously during the playback process it leads not only to deviations in wow & flutter but you can also hear an impact on the sound, I mean I can hear it. And I believe you do too !?
best @ fun only |
Peterayer,
I could not find the Wave Kinetics thread anymore too? Sometimes it happens that a thread disappears by accident. Do you have some information? You suggested this new wonderful thread.
best @ fun only |
Thuchan,
I don't know what happened to the Wave Kinetics NVS thread. I enjoyed that thread because with such a new design, there is very little information in the popular press, so forums like these can be very helpful.
I started this thread because that NVS thread was going off topic and becoming a discussion about speed stability and different drive types. I wanted it to go back to its original focus. And yes, this thread is wonderful and I've learned a lot about the topic of speed, how to maintain it and how it effects the sound.
Threads have a way of disappearing and it is not always by accident. I have no information. Perhaps Jtinn knows something. |
Sometimes threads do accidentally get 'wiped' by an administrator.
It's happened to me twice and when I contacted A'Gon ........they retrieved them.
Have you tried that? |
Dear Thuchan, Syntax' comment on "sound quality not related to speed accuracy" points to the fact that the sound quality per se is not in the speed accuracy.
Speed accuracy in a turntable is an undisputed conditio sine qua non.
If a turntable isn't able to hold the 33 1/3 (and the other speeds required..) it isn't worth discussing about sound quality at all.
In the first shoot out in San Antonio between a serious DD and a serious thread drive turntable, we all 3 - Unoear, Syntax and me - heard that there are sonic qualities which go way beyond speed accuracy-related phenomenons.
Speed accuracy is a basic request for any serious turntable.
Here it starts off - it certainly doesn't end here, it is rather the beginning.
|
Deartoenarm,
agree with your preconditions being set. Unfortunately the reality regarding some running tables looks sometimes different due to weak motors, belts changing the consistency, no built in or used precison control instruments etc. The new TechDas AirForce seems to offer some nice features. On the other hand I would have wished a two sided belt driven system.
best @ fun only |
Dear Thuchan, Our German friends are obviously searching for the new or added preconditions which are yet not known.
If they were known and technicaly solvable then probable
there would be no or less problems with those damn TT's.
Regards, |
I discovered that removing one of the three motors of the Raven AC-3 (aka Raven AC-2)......the turntable was able to maintain far more accurate speed control than with the three motors.
Perhaps the belt stretch or slippage is increased with the three motors?......or the greater contact of the belt on the platter with two motors is the reason?
I can't wait to try a Bavarian thread in place of the rubber belt?
Are you listening D? :^) |
I am listening (... reading ...), Halcro ...;-) ...
Just back from California and Texas and haunted by 9 hours jet-lag.
Will get the "secret rope" off to you on friday.
Sometimes less is more..... |
Dertonearm
If speed accuracy has nothing to do with sound performance but is a seriuos basic request with a design then where would you as a designer place it in order of importance if all else is managed in a design of a turntable?
In other words if the motor/s, speed controller, belt/s are not up to the job holding the speed when a record is being played would this not drastically effect what you hear? |
In_shore, sure - speed accuracy does heavily influence sound quality.
However IMHO speed accuracy is a basic - if not THE basic - request to ANY turntable.
As said before - this is a conditio sine qua non for any turntable.
As this is a basic feature, it is not contributing to the sound quality, but only in negative sense - i.e. if not accurate speed.
So - here it starts, it is not a goal but the mere basic request which has to be meet by nature anyway.
I as a designer simply make sure this demand is meet to the utmost possible as the very first step.
And I for one think this is easy given today's technical tools and options.
Accurate speed can be obtained with idler wheel, direct drive or thread drive.
It can be achieved with belt drive too, but only with much more effort in control. |
|
Dear Nandric,
it is an ongoing quest. I am happy that some new designs appear on the horizon and that Micro Seiki seems to be back.
Maybe we will not see only clouds in the future...
Best @ fun only |
Dear Thuchan, if you are referring to the TechDas as "Micro Seiki back", I wouldn't go that far.
IMHO that design does not resemble Micro Seiki engineering.
We will see what is actually delivered, but what is apparent in the pictures and short descriptions so far doesn't break any new grounds. |
it is very funny, the DD-drive concept divides the users in two seperate fields, lovers and deniers, as sometimes happens with the idler drive as well. From my experience with DD drives I am convinced that a DD motor needs a perfect environment (sorry Halcro). There are excellent examples of "very musical drives", e.g. the Technics MKIII in a fine plinth, the Nakamichi (Micro Seiki motor) or the Brinkmann Oasis.
I found an interesting description at Brinkmann maybe with relevance to the speed/time issue:
The drive mechanism is probably a turntables single most important component. This significance results from the fact that music consists of sounds organized in time. A turntable therefore has to play back a record at precisely the same speed at which it was cut, normally 33 1/3 or 45 rpm. Any deviation, no matter how small, from the correct speed will ultimately change pitch and tempo and result in music reproduction that is not true to the recording.
Our hearing is much more sensitive to short term speed variations, as opposed to long term ones. The onomatopoetic term wow & flutter correctly identifies the underlying issues wow describes continued, longer lasting deviations, caused for example by eccentric records, whilst flutter denotes short-term irregularities best demonstrated by piano tones that fade away with a slightly howling quality.
Let us consider the following example: a 1 kHz tone (1000 cycles per second) is cut into a lacquer at precisely 33 1/3 revolutions per minute. If the pitch is to be accurate, the turntable has to play back this tone at exactly the same 33 1/3 revolutions per minute. A seemingly insignificant variation of 1% would result in a playback speed of either 33 or 33@d revolutions per minute with pitch being off by ±10 cycles. Even people with perfect pitch would have a hard time correctly identifying a 990, 1000 or 1010 Hz tone without a reference yet even brass ears would easily hear the differences in a direct comparison.
Speed precision is perhaps even more important for the musics tempo. For our perception of music to be real, the tempotiming and paceis more crucial than the pitch. This is where the 1% difference would make itself heard far more easily. Considering that a typical record has a playing time of around 20 minutes per side, a ±1% difference would amount to no less than 24 seconds. This seemingly irrelevant deviation would result in either a slightly restrained and darker sound, or a livelier, brighter reproduction of the original event.
In order to meet the claims of High Fidelityno more, no less than music reproduction true to the original the cutting and playback speed have to be absolutely identical. Due to reasons being outlined in the following pages, this theoretical ideal is practically not feasibleturntables are hence (and in the best case) the closest possible approximation to the theoretical optimum.
Two elements determine the rotational speed of an AC based electric motor: the power line frequency and the number of magnetic poles. The formula used to describe this is as follows: rotational speed = line frequency x 120/number of magnetic poles. In countries with a 60 Hz power grid, a two-pole electric motor therefore runs at 3600 rpm (60 x 120/2 = 3600). Each doubling of magnetic poles cuts the rotational speed in half: 4 poles equal 1800 rpm; 8 equal 900 rpm; 16 equal 450 rpm. Theoretically this could be continued even further, however, practically, there are only so many poles one can fit inside a motor case.
Further, each additional pole also increases the motors torque, which in turn increases the cogging effect. DC electric motors dont fare any better either and most are offered in standard 1500 rpm configurations. This showcases the ensuing problem quite easily: on one hand we have an electric motor spinning at 1500 rpm, on the other we have a platter which has to spin at 33 1/3 rpm. The ratio of motor to platter speed is therefore 45:1. Logic dictates that the drive pulley has to be 45 times smaller than the platter.
If we take a platter diameter of 30 cm as an example, this would equate to a pulley of only 6.6 mm in diameter. The contact area for a belt is therefore very small, which in turn increases slippage; which in turn influences speed stability negatively. The problem is further exacerbated by the fact that the cogging is transformed into a frequency range in which human hearing is very sensitive
The power line frequency (and thus the motors rotational speed) can be reduced with frequency converters; however, the cogging problem still persists.
The platter of a turntable can either be driven directly or indirectly. In case of an indirect drive mechanism, platter and motor are two separate components whereby the power from the motor is transferred to the platter through intermediary means. In case of a direct drive turntable, platter and motor are assembled into one and the same unit.
Motor and platter are two separate entities; some sort of medium is necessary to couple the motor to the platter. Typical applications include the following:
> Belt (round or flat; geared or v-belt type; various threads made of synthetic or natural fibers)
> Idler wheel
> Gear wheel drive
The choice of transfer medium is critical since it not only transmits the motors torque to the platter but also all motor-based interferences, among them the motors cogging, which compromises speed stability since the platter is not driven continuously but somewhat jerkily instead. The more direct the connection between platter and drive, the more directly these interferences will be transferred. An idler wheel for example couples the motor very directly to the platter. As a result, the cogging effects are more pronounced; in the best case they manifest themselves as a slight flurryness of the sound; in the worst case through clearly audible distortions.
Because of the reasons stated above, most turntable designers therefore prefer a softer coupling between the diameters of the motor pulley and the platter. Even tiny discrepancies in the belts uniformity will have a serious impact on the platters speed stability. Consider the following example: say a DC motor running at 1500 rpm drives a 20 cm sub-platter via a 1 mm thick flat belt. A discrepancy in tolerance of only 1/100 mm will have a net effect of 0.9% wow & flutter on the platter!
Countering these effects demands substantial efforts in the design of a belt driven turntable. Heavy platters (12 kg or more) and low rpm motors tend to mitigate these side effects to the point of not being significantly audible.
Studios (radio stations in particular) demand quick start-up times turntables typically have to reach their correct speed within half a revolution. For LPs this means 0-33 1/3 rpm within 0.9 seconds. Such acceleration figures can only be achieved through use of high-torque motors and correspondingly tight coupling between the drive and platter. It isnt a surprise then that for decades idler wheel drive designs were the de facto standard in studio applications.
But idler wheel turntables also had seriously high maintenance costs in order to be up and running 24/7 and to avoid rumble and other sound degrading issues caused by worn out idler wheels to affect the sound negatively.
Thus out of necessity, in the late 1960s manufacturers of studio turntables began to look for
low(er) cost maintenance alternatives. They came up with direct drive, whereby the platter was placed directly on the motors shaft, ie the stator was mounted around the bushing and the shaft was used as the rotor and voila, the goal was achieved; at least in theory.
But start-up times of less than 1 second necessitated high torque motors, which designers achieved byusing motors with 32 and more poles. The penalty they paid were heavy cogging effects accompanied by high wow & flutter numbers. The cure was found in quartz locked motors and phase locked regulators; which corrected for any deviations from their preset with an iron fist.
On paper at least, these corrected direct drive turntables boasted hitherto unimaginable low wow & flutter numbers down to 0,001%. But the rigorous iron fist regulation prevented the platter from spinning smoothly; instead, the regulation caused the platter to oscillate continuously between speeding up and slowing down.
These start/stop motions translated into an unpleasantly rough and hard sound; odd as wow & flutter numbers in the 0,001% range are deemed inaudible. Once the direct drive technology had gained a foothold in pro audio applications, the benefits of mass production (ie. trickle down effect) made sure that very soon even $100 turntables were equipped with direct drive and advertised as having less than 0.01% wow & flutter. This is precisely where direct drive got its bad rap sheet.
Under closer scrutiny however, this assumption were based on some misunderstandings. For one, in home audio application use, turntables are not really required to reach 33 1/3 rpm in less than a second, thus 32 pole motors and phase locked regulators are not really necessary either.
Finally, one more relatively unknown factoid: while it is common knowledge that direct drive turntables became popular in the late 1960s, their actual invention dates back to a small Swiss manufacturer in 1929. The name? Thorens, who enjoyed and even today is looked upon with great respect for their idler wheel and belt driven classics. |
Dear Dertonarm: Like with the Wave Kinetics and Onedof new TT designs now you follow dimish every new TT design like this one Air Force One.
Why in one way or the other do you want to dimish the other designers efforts even when you never heard those new designs?
I can't see any other TT designer that already dimished your coming TT?
We customers need alternatives and with out real and precise foundation why comment/dimish/attack a new TT design what/that you never heard it and never has on hand?
I know that your design is wrong but I don't care about because is your design not mine.
Regards and enjoy the music,
R. |
Dear friends: Do you think here could exist speed accuracy?
https://picasaweb.google.com/hfeiner/TWOTURNTABLES?authkey=Gv1sRgCOy02-j1puykKA#5678170499062229282
that's is a JC/TH/H contribution.
Regards and enjoy the music,
R. |
