Turntable speed accuracy

Dear Raul: If one has built a turntable than which none greater can be conceived, then there's no need to listen to others, except as a form of idle amusement.

Funny thing that as soon as a NEW component - which none here has heard nor seen in real life so far - isn't praised ahead it is "diminished".
It is not.
It is just not praised ahead and there is nothing new displayed.
Simple.
Some will buy it - some won't.
It will eventually earn some laurels and I will most likely be one of the first in the western hemisphere seeing and listen to it.
Turntable designer disclaimer ...;-) .....

Dear Dertonarm/Syntax: +++++ " 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.... " +++++

IMHO that statement is plain wrong: it is as to say that a phono stage " basic request " is no RIAA deviation/gain with no noise or in an amplifier 0.01 ohms output impedance or in a cartridge flat ( cero deviation ) frequency response or whatever with any kind of audio items.

The premise that those are " basic request " audio device in the designs does not means the audio product already achieved only because are " main request ".
In our imperfect audio world there are almost none of that " main requests " in any design that fulfil those main requests.

So to assume that main requests are all there is IMHO a wrong assumption.

TT's is only an example both of you can take any audio item and you will and know that the " majority " does not fulfil even those main requests. Mediocrity is the name of the game with a few exceptions.

Now, speed is only one factor in the whole TT design and in the final quality level performance.

We will see how good the " main request " on a TT: neutral/accurate can be match by all those new designs including yours.

Regards and enjoy the music,
R.

I am not assuming that the main requests are all there, - in fact I see that in many cases this is just not the case.
The request itself is nevertheless a conditio sine qua non in the context of the technical blue book of ANY turntable.
That reality in many instance doesn't follow the request doesn't mean the request is wrong.
Mediocrity may be the name of the game with few exceptions.
It never was for me.
To me it is always and only about best possible results - not was a majority may have problems in nor whether a majority of components may have problems with.
IMHO speed accuracy is so basic a request by nature for a turntable that it is not worth discussing at all.

Speed accuracy has inspired two more companies bringing out devices for checking. Allnic with the SpeedNic turntable speed checker and Dr. Feickert's free Platter Speed speed check software (for i Phone or Android) - learning from MF...

best @ fun only

Dear Thuchan, the Speednic by Allnic looks neat. Especially as it allows adjustment during play and thus taking into consideration stylus drag.
Thank you for the hint.
Cheers,
D.

From what I can see and read about the Speednic......it seems no different to a Kab strobe?
Can anyone explain to me how the Speednic competes in any way with the Timeline?

I downloaded the iPhone app and did some testing. The same test record that I used before also has a track with 3150Hz. As I mentioned before, I measured considerable runout in my test record which by itself causes some audible Wow when playing constant frequency test tones. The center hole of this test record has a slight amount of play on my tt spindle. After much patient work to minimize the record runout I got the following measurements: Mean Freq: 3151.3, Raw Frequency: -0.22%/+0.24% relative, -7.0Hz/+7.4Hz absolute. Lowpass Filtered Frequency: -0.02%/+0.01% relative, -0.5Hz/+0.5Hz absolute. I'm guessing that the filtered values subtract out the record runout. The reason I conclude that is as I meticulously adjusted the record on the platter to minimize runout, I had raw numbers as high as -9.8/+10.7Hz while the filtered values never exceeded 0.03%.
Another observation: The original Mean Freq was 3155.6Hz based on my setting using the strobe disc. I adjusted speed down and can certainly work some more to dial it in at precisely 3150Hz. The other observation is that holding the iPhone while taking the measurement adds more error. It is sensitive enough to pick up hand movements. I set the phone on a table about 1 meter away from the front of one speaker.
So how does my humble BD table compare to some others?
btw- I have a record clamp. So I adjusted the record relative to the spindle and then clamped the record down.

It seems like none of us read each other's posts, except Raul and DT, so that they can reach immediate disagreement. A century ago an American writer named Ambrose Bierce defined "conversation" as a social interaction wherein I wait for you to finish talking so I can say what I want to say. In any case re turntables, DT is right. The first job of a tt is to get speed right. Raul used to argue that a phono stage that does not do riaa within 0.1 db is fatally flawed. You can't have it both ways, Raul.

Dear Lewm, disagree. I think they read the posts but they understand it in a different way as you, me or others do.
This is not because they not only have a more sensitive scope but maybe they have a more sensitive feeling too when reading each other`s post.

Nevertheless I do think in this topic we are all not far away from each other. We all agree that accurate speed is an important condition or precondition for enabeling a good sound quality.

Of course there are other factors having also an impact on good sound quality, the bearings quality (e.g. air based or other quality attributes), the motor´s quality (maybe also fly wheel or more motors), the platter`s quality (material, weight, air lips) the belt, thread or idler wheel`s quality, and last not least the interference and the implementation of all these turntable parts. Enough stuff for some more threads...

best @ fun only

I found the owners manual online for Adjust+ and some reviews. As I surmised the low pass filter is set for 0.56Hz to eliminate record runout. I was considering drilling the center hole out a few tenths of a millimeter on my test record, but I began imagining what a catastrophe that would be me loose with a hand drill with one of my precious records. Fortunately this iPhone app cancels out the record runout for you. Pretty cool app.
Regarding the tt bearing: I do my own maintenance on my tt. Periodically I breakdown the tt and clean the main bearing. I re-lubed last time with a synthetic grease. I think it made the tt sound better. Anyone else had that experience? I have never touched the motor.

Bearing lube for dd turntables is yet another controversial subject. Fortunately, the rotation is so slow and relatively low stress that almost anything will do to prevent bearing damage. One guy who restored my L07D insists on only a certain weight of a certain racing motor oil. I am sure it is overkill.

when it comes to bearings/ motors and platters I see a difference between the vintage designs and most of the modern turnables. The  service principles say I need to lubricate the EMT' s bearing every year, oiling the motor once in years. Introduced in 1951, the EMT 927 is a massive turntable with an aluminum chassis,  meassuring  6 7. 5 x 52 x 21 .5 cm with a weight of 80 pounds. The platter has a diameter of 44 cm and sits in an amazing precision ball bearing. The bearing shaft is 16.6 cm long and has a diameter of 2 cm! The motor itself is massive. It looks like an industrial motor, 13.5 cm in diameter and 20 cm long! It is a 3 phase synchronous type with phase shifter.

The big MS designs have an oiled, capsuled bearing which should keep a man's life. The massive platters have a weight of 40 to 50 pounds, the full table up to 170 pounds. The Micro Seiki motors are very precise (with a competent controller) as the Continuums motor is as well, a linear 3 phase AC-24V DC Brushless design with integral optical decoder. You need looking at these parts to get an understanding why the usual small motors used for todays TTs are a joke! The Continuums platter has a weight of 60 pounds. I have put an image of the self lubricating bearing on my page to show the difference.

I do understand when Dertonearm questions the quality of new developments against the Micro Seiki, EMT or Continuum standards. In all the mentioned designs the mass does its job with inertia and resonance control. All that makes for a very good turntable in my opinion. And in all designs precision is of importance. 

best @ fun only

Very interesting thread!

Obviously the question how important speed accuracy actually is and how to achieve best results challenges TT designers and puzzles music lovers like us for … as long as vinyl records exist!

Maintaining constant AVERAGE speed of 33.1/3 or 45 rpm has been accomplished, but I don’t think that AVERAGE speed accuracy is extremely critical. The real engineering challenge is to maintain constant speed at any given time in any infinitesimal small time interval. Not everyone might agree, but I don’t think this engineering challenge has yet been accomplished. Maintaining absolute constant speed against an ever changing load is … probably impossible!?

To illustrate my thoughts I would like to use an analogy.
Imagine a car rolling on uneven beams of a railroad track being pulled by an engine which in turn rides on the smooth train tracks. The car in pull is our platter, the bumpy beams represent the ever changing load caused by stylus friction, and the pulling engine is our electric TT motor. Our goal is to keep the car in pull at absolute constant speed (measured in the horizontal plane). Forces caused by the tires hitting a beam instantly try to slow down the car in pull and the pulling engine tries to work against this load change to maintain desired speed.

It seems obvious, that a strong engine is beneficial to minimize speed changes caused by load changes. It also seems obvious, that using a flexible rubber band to connect the pulling engine and the car in pull will make it even more difficult to maintain constant speed of the car in pull. No matter how strong the engine, the flexibility of the rubber band will allow the car in pull to vary the distance between itself and the pulling engine caused by ever changing forces from climbing up each wooden beam.

In this analogy the rubber band represents BD designs, while a stiff beam connecting the car in pull with the engine would represent idler drive designs. A DD turntable places the engine into the car in pull itself.

Quartz controlled speed regulation of any TT drive system requires a speed change to actually happen first, before it can be detected and in return corrected.

In contrast, unregulated A/C motors (Garrard, Lenco etc.) actually don’t try to maintain constant speed. If we ignore that our rotating system has a mass, the resulting platter speed of an unregulated A/C motor drive system becomes a direct function of the applied friction. The absolute speed change resulting from a load change depends on the steepness of the torque-speed curve of the electric motor in the area of operation.

The link below shows several characteristic torque-speed curves of induction A/C motors (Figure 9).

http://inductionmotor.co.in/shaded-pole-ac-induction-motor.html

The famous vintage idler drives (Garrard 301/401 and Lencos L75/78 for example) use shaded-pole induction A/C motors (curve on bottom).

I did some measurements on my own Garrard 301. When working against friction caused by the platter bearing as well as needle drag, the motor operates at about 99.6 % of no-load speed (very close to the right end of the torque-speed curve on the chart). Only the steepness of the curve in this area determines the resulting speed change from a certain load change (increased bearing friction from additional weight on platter for example).

Accepting the fact, that achieving constant speed is literarily impossible, the real question to me becomes, which design approach results in sonically more acceptable speed changes caused by the constantly fluctuating load from needle drag.

The regulated drive system requires a speed change to occur first to detect and correct the speed by applying more torque. In an unregulated A/C system speed changes also occur, but no mechanism tries to correct the speed back to the desired nominal speed. Both systems accept small speed changes as a result of load fluctuations.

Even if we were able to precisely measure these extremely small effects, IMHO only our ears can judge which type and characteristic of speed change is more acceptable to our hearing. The mix of compromises that each design comes with and the effect of all of these compromises to our hearing determines what type of drive system is able to produce most pleasing results.

I went thru my own little try and error TT experience and am by far no expert on TT designs. What I do know though is (even though IMHO none of the existing designs achieves it) that absolute speed accuracy is of utmost importance to the musical presentation. The sonic difference between low and high torque drives needs to be experienced to understand the impact to the musical presentation.

I’m currently using a Garrard 301 with Loricraft’s large PSU providing 220 Volt and 50 Hz to the Garrard, which – compared to driving the Garrard with 110 Volt at 60 Hz, using a smaller pulley – “steepens” the motor’s speed-torque curve in the critical area close to no-load speed.

No matter what drive system is used, I’m convinced that a high effective torque drive is a must, and that any flexible element able to store energy between motor and platter will work against the goal to minimize speed changes from load fluctuation.

I found TT information on Arthur Salvatore’s webpage very interesting - especially his idler drive section.

http://www.high-endaudio.com/RC-Tables.html

Tonywinsc,

For records with holes out of centre my engineer mate simply uses a thread file ( very small round file ) to open the hole up only in the direction you need to move the record to centre it. Then puts a marker on the label to indicate which side of the elongated hole butts up to the spindle. This seems to work reasonably well.

Dover, good suggestion. I have a small, round bastard that should do the trick. I might give that a try.

The Allnic SpeedNic works pretty well. I have put two images on my page (last two images when scrolling down)

best @ fun only

My KAB strobe works pretty well also.
With it....the Raven keeps perfect speed.
If you want to be happy.....use a strobe.
If you want the truth.....use the Timeline :^)

Halcro put it in the most precisely manner. The Timeline may be frustrating in it's accuracy, but then it is not the Timeline's fault. Very interesting too, to watch the laser beam over the whole record side ( record it with a camera - it is too boring looking there all the time).
On many turntables one may notice shifting back and forth and correction with controlled motors during heavily modulated passages.
A nice lesson in stylus drag and it's not linear nature.

I filed the hole in my stereo test record. I improved the runout a bit. According to the iPhone app, I now have the raw Wow down to +/-0.16%. The filtered didn't change, -0.01%/+0.02%. The total spread within the published specs for my tt. With a little more filing of the center hole and more work/patient effort to center the record on the platter, I could improve the raw values even more. I have a feeling that I will be bringing a dial indicator home from the machine shop at work to measure record runout with extreme precision. I will likely be filing the holes on my records now to perfectly center them. My neurosis is ratcheting up a level, I think.
Anyway, this app is nice, you can play the test records 3150Hz track at 45rpm and this app will detect the higher frequency and tracks the speed at 45rpm automatically. I must agree having seen it live with this app. Having the motor via a belt separate from the floating chassis/platter is a deficit. The slightest vibration/movement of the floating chassis causes a speed error. It is a small error, but still there.

Dear Halcro, you´re right the Timeline is perfect. The Allinic provides the advantage you may use it as a fixed installation and you do not need to hit the mark at the wall which is a bit of trial and error moving the Timeline forth and back - but of course after a while it works brilliantly.

You have two turntables and only one strobe - this looks like an imbalance :-)

best @ fun only

Dear Thuchan,
I don't use the Timeline as a record weight as I find it too light.
Therefore I use it from one turntable to the other only if I want reassurance? :^)
Cheers
Henry

Purchased a Timeline last year after my Clearaudio strobe stopped working. The cost to replace the Clearaudio strobe was close to the price of a new Timeline.
Having used the CA since I bought my Verdier back in 2006, I found it easy to use and was able to set and forget about the speed. Enjoyed the music immensely on my table.
Since using the Timeline my perspective has changed.
At first I could not believe that the speed of my table was not accurate or stable at 33 1/3 rpm and the fact that it drifted all on it's own.
Then play some music and watch the Verdier slow down as the Timeline easily demonstrates. I use green painters tape, two pieces against the wall about 6 inches apart.
Quite frustrating. Did I worry about such a thing when I had the CA, clearly not. But now that I know that the speed is off, am always conscious of it. Obsessive no, but aware of it all the time. Do I enjoy music less on the Verdier, of course not but.
Have taken on the task to make a battery powered unit with a charging system like the "Callas unit" and will rewire the motor for the Verdier instead of using AC.
Hope that this will solve my speed issue on the Verdier.
My direct drive tables do not have this speed drift issue at all. Great video Halcro.
I think that Halcro nailed it in his post above.

"If you want to be happy.....use a strobe.
If you want the truth.....use the Timeline :^)"

My two cents, take care.

Accuracy or sensitivity of speed monitor device should be proportional to (1) distance of sensor from center of rotate (longer radius is better) and (2) stability of the strobe at 60 hz per second. Ergo in theory the kab strobe (battery powered and not subject to AC line frequency variations) should be superior to timeline (batt power but v short radius) and to allnic (worst, with AC line power AND short radius). Admittedly, the kab is least convenient.

Tonywinsc, you have used the term "runout" several times. I believe this is intended to relate to the accurate centering of the record. But in all my years in this hobby I've only heard the term runout applied to the area at the end of the recorded material where the stylus rides a continuous circle. Am I the only one not understanding this term?

Now back to the basic subject of this post. It seems to me the motor/bearing/platter have four tasks:
- providing a stable platform for the record,
- not introducing any noise which may be picked up by the stylus,
- rotating the record accurately at the desired speed (this might be considered the overall average speed), and
- maintaining that speed through the mili-seconds when interference might occur from imperfect motor rotation, power line fluctuation, stylus drag, etc.

If I am correct, it is the last of these tasks which may be the most difficult to achieve. I've never seen a Timeline, only a demo video. But I have two comments. First I agree with Lew that the distance to the sensor mark would be important. But secondly if the mili-second interference does not occur at the point when the sensor mark is reached the error may not be noticed. In other words the speed might have recovered by the time the sensor hits the mark. Does this make sense or am I misunderstanding something basic here?

Dear Lewm,
the Allnic SpeedNic is battery powered and not so bad as you think...
also it allows adjusting during play.
I am not selling this product :-)

Rugyboogie,
you are in very comfortable situation with one running turntable ;-)

best @ fun only

Rugyboogie, I meant with one belt drive TT, sorry!

best @ fun only

Runout is the measurement of the eccentric motion in a rotating body. What I have been talking about in terms of a record is that the center axis of the record grooves are not matched precisely to the center axis of the platter. (Shaft runout would normally be measured in V-blocks in a lab and would consist of a combination of roundness as well as straightness of the shaft.) Additionally, the platter can have some runout- hopefully that is nearly unmeasurable considering the cost of some of these platters. The best way to measure the runout of a record would be to measure the swinging motion of the tonearm when it is playing a round groove at the inner diameter of the record. It would be difficult to measure while playing in the music groove since the tone arm is continuously moving inward towards the center of the record. The OD of the record is likely not that round and not necessarily tied dimensionally back to the music groove. I would say that if you can discern a swaying motion in the tonearm with your eyes as it is running in the music groove, then the runout is probably high. This was the case with my test record. But even then, I could hear the Wow only when playing pure test tones.

My mistake, Thuchan. So therefore the allnic and the timekeeper would be about the same. I thought I had read elsewhere that the allnic light needs to be plugged in to AC.

Thanks Rugyboogie,
The video was very amateurish but I think....made its point.
Hollywood has not been ringing though which is puzzling?
You are one of the 'brave' ones amongst us....having purchased the Timeline only to find disillusionment with the macro accuracy of most belt-drive turntables.
However I believe the truth can help you.....and you happily have plans to correct the situation with the Verdier.
I certainly wish you luck.

Pryso,
Yes you are misunderstanding the principle of the Timeline as also Lew continues to do despite me trying to explain it on 2 or 3 occasions?
A turntable......any turntable......will not 'make up' for lost speed.
If a turntable did this......it would simply be unlistenable as it would never be revolving at the correct speed. This is a common misconception about servo-controlled DD motors.
A turntable must revolve at a 'constant' speed. If that 'constant speed is not exactly 33.3rpm......it is only a matter of 'pitch'.
When something occurs to 'alter' that speed momentarily.......it will almost always slow it down (stylus drag). When the motor detects that 'slow-down'....it will compensate to regain its 'correct' speed. It will NOT 'correct' that slow speed to another 'incorrect' FAST speed?
Thus the original 'altered' speed (due to stylus drag)....is a historical event that the turntable motor does not 'remember'.
The Timeline however.......will keep the record of that altered speed as long as it keeps revolving and thus the laser line will NEVER 'recover' to once again hit the mark on the wall.
This is the difference between a strobe and the Timeline. With a strobe....any speed change is so quick that a blink of your eye will simply miss it and the strobe has regained its 'correct' speed before you ever see it. With a strobe....there is no 'record' of the speed change.
With the Timeline.......a 'running' record is automatically kept and cannot be erased.
I hope this is somehow clearer........but the way many here are discussing the accuracy of different strobes to the way the Timeline is designed to function......simply leaves me open-mouthed :^O

Dear Halcro, 'but the way many are discussing ...strobes (versus) Timeline...symply leaves me open-mouthed.'
You are suggesting the lack of intellect while it is about simple psychology. A phenomenon which can be observed in nearly any thread.

Regards,

Halcro,
I think you're on the wrong track ...
Simple physics dictates that speed must "swing" above and below 33 1/3 rpm in order to average out at 33 1/3. A speed change to below 33 1/3 HAS to occur first, before it can be detected and then corrected by applying more torque. If a drive mechanism does not "make up for lost time", the timeline laser would slowly, but constantly drift. The fact that these speed changes are very very small make it difficult to understand, but they have to be there in order to be corrected. Without any servo circuit measuring and correcting speed changes, the speed-torque curve of the electric motor would have to be a vertical line ... and there simply is no such thing.
You are right, it is very problematic to ceorrect speed in a way that our hearing tolerates it. The very high torque drive system of a Technics SP-10 MK3 or a JVC TT-101 sound much different from a low torque direct drive, but they both are able to maintain correct AVERAGE speed of 33 1/3 and the timeline laser will not show a differnce.

You're right of course Decibell.
The 'correction' to any stylus drag speed reduction is so instantaneous...that we cannot see it on the Timeline.
What I really meant to say was........once a speed shift has occurred....without any instaneous correction.....no turntable motor will 'speed up' to 'remove' that abberation over the course of a few revolutions and thus restore the Timeline laser to its mark on the wall?
Yet with a strobe.......all will seem to be runnIng perfectly immediately after a speed shift (or even during if you blink).

Your timeline device is averaging speed. It is not giving you an instantaneous reading. The laser pulses every 1.8 seconds. As long as the turntable achieves one revolution in 1.8 seconds, the laser spot remains stationary. Your turntable could be speeding up 25% and slowing down 25% in one revolution and the timeline will happily show a stationary spot on the wall as long as the platter rotation averages 1.8 seconds per turn. The best way to determine how your turntable is behaving is to look at speed real time. One way is some type of encoder with the output to an X-Y plotter. Another way is to play a record with a fixed frequency such as 3150 Hz. The inherent errors are 1) accuracy of the recorded frequency and 2) record runout. Using an FFT analyzer you can see any speed drift realtime. A good substitute is the iPhone app. It seems very good to me. It will show you your turntable wow and flutter real time and filters out the 0.5556Hz frequency caused by any record offset to the platter.
I would like to know if anyone's turntable wow and flutter measures less than 0.01% regardless of drive type.

If you take a look at one of the old brochures for the Denon DP80 (I think), they present an actual plot of instantaneous speed v time. The DP80 is not perfect in this graph, but Denon claim it was superior to the un-named competition. This is really just to say that the old guys understood and were able to graph this phenomenon.

Dear Lewm: Yes, they did indeed. These are exerpts from a Sony research in 1975:

++++++++++++++++++++++++++++++++++++++++++++++++++++

Ordinary Motor Servo System
The design object of a turntable motor servo-control system is to
have the least amount of change in rotational speed when the motor
is subjected to changes. Load conditions, such as application of
stylus pressure on the record and the change in fractional resistance
between stylus and record groove. Fig. I shows the static characteristics
of the servo system.
When the motor load torque is to and the supply voltage is Vo, the
angular velocity is Po. If the load increases to tl, the angular
frequency goes down to Pi provided that the supply voltage is kept
at Vo. In this case, th8 amount of change in angular velocity per
unit change of load is as shown below.
6P Po-P_ I
KT- a_- - ?,-7o - Do I-o.
Do=Fluid resistance
In order to bring the angular velocity back as close as possible to
Po, the supply voltage must be increased when the angular frequency
is lowered from Po to Pl' The amount of change in angular velocity
of the motor per unit of supply voltage, Ky, is shown as follows:
81_ KT
Kv=_,V - 0o I-b
KT = Cons'i'anf of 'torque .generefion
The amount of change in voltage per unit angular velocity, K, is expressed
as follows:
aV
K- FC
AW
_p in FiE. 2 is the amount of change in angular velocity after the
servo system has stabilized and is shown as follows:

Ap = I+K Kv
_7 = chanqein Icedtorque
i + KKv in the preceding equation Is called the loop gain. From the
equation 1-a and 1-b the following is obtained:
f
P Do
---- I-C
Ay I+KKV
Thls shows that curve S In Fig. I which indicates the amount of change
In angular velocity after the serve has stabilized, is improved when
multipled by the loop gain over the change in angular velocity before
the serve is stabilized. Above, we discussed the function of the serve
system with a change in load torque under DC conditions. In the case
of a change In load torque under AC conditions, the relation among various
parameters in shown in Fig. 3.
The dotted lines in Fig. 3 show the characteristics of disturbance suppression
by the moment of inertia of the motor rotor and turntable.
The solid line shows the characteristics after the serve is stabilized.
Fig. 3 is also expressed In the following equation:
Po I -.f
glo= (I+KKv) j
I.
z_P(Jl) Do
A7 (,.Pt,) - I,KKv t-9
when J_ ¢ d'_co
Therefore,
aPfJ_)
I-h
/',7'(_'t,) J-d"bo
This indicates that in order to obtain higher suppression of external
disturbance, it is necessary to make the moment of inertia of motor
rotor and turntable as well as the angular velocity response of serve
system larger. For example, under the following conditions:
,.,T=ZOO(§.cTn. seci), J_o --Z/-(X lO (red/acc)
Stylus point from spindle = 15(cra)
Stylus pressure = 3f§)
Coefficienf of frichon, xz =0.4
_Y = I_ x 3 ×O.Z..=I-18 (9 .cra)
The amount of change in angular velocity of the motor spindle dP is,
therefore, expressed as follows:
2
Ap = J_L_ ' AZ = ZOOx Z 7_x IO X 18 = I,z+33XIO -3 (md/sec)
· = O.OI37(rpm)
This change in the standard speed of 33 1/3 rpm in percentage,_, is:
/
aP O.OI37
?_ ---- _P_3__- X IOO --- lOC X IOO = O,Oql (%)
3
Phase-locked Motor Servo System With Quartz Generator
As discussed above, conventional servo system requires detection in change
of angular velocity for compensation in changes of speed. Therefore, unless
the moment of inertia in the mechanical system is infinite or the
angular velocity of servo response is infinite, it is impossible to avoid
changes in speed totally. Increase in the moment of inertia will result
in shorter life of the motor/turntable bearings and slower start-up time.
Increase in angular velocity of servo response has also its limitations.
The phase-locked servo system utilizes the prinipal that if a change in
angular velocity is converted to a change in phase, the conversion constant
becomes infinite at DC. The change in angular velocity P(t) is expressed
as follows:
Pit) =A PcosJ1t &p: arnountchangedin
angular velocity
The change in phase f8 (rD;n this case is-
_(:t)=fPtt)dt- AP sin Zlz / ./ _b
Therefore, the transfer function H (_) is =
Therefore,¢h¢¢rans_r fu_ffion H(_) is:
H(g) = -p-=(t) ..I... 2-_
Pit) jJ_
The preceding equation 2-a indicates that when a change in angular
velocity (_) is zero (or DC), the conversion gain becomes infinite
and the phase is always 90° behind regardless of angular velocity.
The transfer function, HT (_-) is the change between angular velocity,
and voltage is expressed as follows: .
Ka
Hr (Z1,)= K,_ H(_%)=
K_: Cons-Cainntconvertingchange
inphase intochange in voltage
Fig. 4 shows the block diagram of the serve system with HT _ in the
serve loop, and Fig. 5 shows its disturbanee suppression characteristics.
In Fig. 5 the dotted lines show the disturbance suppression
3

characteristics of the moment of inertia in the mechanical system.
The solid line shows suppression of characteristic after the velocity
detection servo is stabilized. The broken line shows the characteristics
of servo system including the phase comparator system. As shown,
compared to the system only with velocity detection, the phase comparator
system improves the disturbance suppression characteristics when
the torque disturbance angle frequency is belowS; and when there is
no disturbance _.=O), the change in turntable angular velocity_p becomes
zero, or in perfect equilibrium. If there is an error in the reference
itself, to which the angular velocity of the motor is compared,
this will of course result in an error in motor speed. In the case of
the Sony PS-8750, a quartz generator is used as the reference source.
Since the speed error of the motor in this case is equal to that of the
generator, it is kept to below 0.003%.
The effect of the stylus pressure and friction between the stylus and
record groove is shown in Figures 6-1 and 6-2. Fig. 6-1 shows that
with "velocity only" servo systems a two-gram stylus pressure on the
outer grooves results in approximately 0.02% slow down inturntable
speed in addition to the speed fluctuations of about 0.014% caused by
the audio signal modulation in the record grooves. Fig. 6-2 shows
speed stability of the phase-locked servo system. As it is shown,
there is little effect from stylus pressure and the change in friction
between the stylus and grooves on the turntable speed. The frequency
of the external disturbance stays mostly below 1Hz. Therefore, as shown
in Fig. 5 it is suppressed very effectively with the phase-locked servo
system, j_In the PS-8750Jcase, the phase-locked servo responds below 1.4
Hz (fc =_-_= 1.4 (Hz). At around 0.07Hz where most of the disturbance is
found the suppression is approximately 20 times greater than that of
the "velocity only" servo system. If the same effect is to be obtained
with the servo system without a phase comparator, 20 times more moment
of inertia is required in the mechanical system.

++++++++++++++++++++++++++++++++++++++++++++++++++++++

Denon use/used that PLL system as other manufacturers.

Regards and enjoy the music,
R.

Dear Rauliruegas,
This is very interesting! Does this document exist on the web to be downloaded? If not, can you email a copy with graphs etc.? I would be very interested.
Thanks

My friend Raul. Thanks, got it!

Or as was once suggested, "it's as clear as mud but it covers the ground."*

* Observation by a non-engineer.

Dear Decibell: Please email me.

Regards and enjoy the music,
R.

Dear Pryso, *now wasn't that non-engineer Harry Belafonte strollin' down the beach in sunny Jamaica with his father who tried to explain to him the thing with the birds and the bees .... ?

Dear Peterayer,
Do understand. Sometimes threads are dissapearing without the community being informed for what reason this was done, if it happens accidentically or because someone asked for deletion. In my case I asked Audiogon. on one thread it was restored, on another thread I did not get any reply, maybe a dealer wasn't` happy - just wondering ...

Best @ Fun Only

hi there-------------------------------testing only.

Raul try testing the timeline it goes like this - - - - - - -

Dover, that was funny. :-D

The thread "TTWeights table and Timeline accuracy" is mysteriously closed but at least we still have this thread to talk about speed issue. I don't want to stir up the pot and point fingers at certain brands but I still enjoy discussing speed issues in turntable designs.

We are still waiting for Lew to report back on his Timeline experience. :)

_______

I have just fitted a thread drive to replace the rubber belt on the Raven AC-2 (thank you Daniel for the Bavarian thread)........and apart from the increased accuracy in speed constancy over the original rubber.......the actual improvement in sound is astonishing?
The bass appears to have added a half octave in depth, the clarity and dynamics have improved and the sense of excitement and realism on every track is palpable.
Is there more to this than speed consistency?

Incidentally......I had to reset the speed on the Raven motor controller because of the differences in force transfer between the rubber and the thread and I used the KAB Strobe initially to find the 'ball-park' setting.
I then set the 'correct' speed using the Timeline and the adjustments to the controller were quite severe. I'm not talking fine adjustment here.........it required about 7 or 8 presses of the 'faster' button to reach 'correct' speed over that settled by the KAB.This is rather a serious indictment of the KAB which simply cannot be correct?
I don't know if it's just my strobe or whether this is endemic to the functioning of the KAB?
I know that the Timeline is exact as it agrees 100% with the speed indication on my Victor TT-101 DD turntable which is quartz locked.
So the question to those relying on the KAB or other versions of a strobe to set the speed of their turntables........you may wrongly believe your speed is correct.
And to those who state that it doesn't matter......how do you know when you haven't heard?

I'm sure because TTWeights places many ads here on Agon they had a BIG say in why the thread was closed. My own search for a table that has spot on accuracy still continues......

I have just replaced the rubber belt on my Raven AC-2 with the Bavarian thread sent to me by Dertonarm ( thanks Daniel).
The speed consistency is slightly improved with this thread drive but the sound of the turntable has been somewhat transformed.
There appears to be a half octave of added bass together with an increased level of excitement and realism to each and every track and record.
Is there more to the drive method than pure speed accuracy?
When I changed to the thread drive, I needed to adjust the Raven motor controller to correct for the differing characteristics and I used the KAB Strobe to quickly get me to the 'ballpark'.
I then installed the Timeline and was shocked to find how inaccurately the platter was now running? I needed to press the 'UP' button about 7 times to reach the correct speed on both 33.33rpm and 45rpm.
When the speeds were corrected with the Timeline......the KAB Strobe indicated incorrect speeds!?
I know the Timeline is correct as it agrees exactly with the speeds on my Victor TT-101 which are quartz-locked.
Perhaps it is only my KAB Strobe which is faulty?.......but I urge caution for all those relying on strobes to set their speeds?
And for those who claim that speed accuracy does not matter.........how do you know if you haven't heard it? :^)

Halcro, interesting and thanks for sharing. What's very interesting is if you already had it set-up for accurate speed with the belt which I assume you did and by just installing the thread the variance.

Is the thread now longer then the belt size was? Not the same tention possibly?

Another tweak to try would be with your table is to use only two motors, have one motor on each side with separate threads but only one operational motor.

Are you not concerned with the thread maring the platter POD material? D mentioned someone else whom did this and it did such so this person has since moved onto using a 1/4 mylar belt and actually has the two motors set-up as mentioned above. Table being isolated separate from the motors.

I also have the thread on hand and my table being the TW BK with an almost all copper platter being mostly different than yours I'm concerned and have yet to do it, last thing I want to do is damage the looks of the platter.

On tables like the MS appear to be no issues due to the different plater material, gun metal or stainless.

Dear Halcro,

your new experience with a thread driven Raven sounds good.
Next, you could try this:
- disassemble the three feet from both of your motor housings
- set up the housings flat on some kind of damping mat (a piece of anti-drone mat for washing machines would help)
- rearrange the strings

Now the motor housings are no longer able to wobble slightly on their feet (that's particularly the case when strong tension of the belt/tape/thread is applied). In my experience this has also positive effects on speed consistency and sound improvement.

Halcro great to see you trying the thread drive. The pulley shape should be concave for thread drive so it self centres and does not ride up and down.
Dev I have been using my thread drive final audio Parthenon for over 20 yrs with silk thread , surgical silk, quite high tension and there is only a very faint mark on the platter, no wear.