Turntable speed accuracy

Dear Dover, I don't. But I am surprised you were even able to perceive (visually) a 2-mm displacement, although I guess over time you could measure a larger distance and then extrapolate backwards to determine 2mm per revolution.

Lewm - I positioned vertically a silver metal marker, about 25mm wide, on the wall - it was quite easy to check the moving distance from the leading edge.

Dover, it has been sitting for some decades, I suspect.

The trust bearings are interesting. They are a set of polished platforms that reside beneath the platter. The drive shaft comes through the center and has nothing to do with them!

I almost bought the timeline. Glad I didn't. using a Fluke digital multimeter is a more accurate way to set your speed, rather than trying to look at a laser being somewhat stationary on a wall. Use a test record at 1000Hz and connecting the Fluke to the output of the phono stage. For 45 rpm, the same 1000 Hz tone should read 1.35k Hz. The Fluke cost about $125.00.

Rockitman,

I have been doing almost the same. Card as test LP 1khz tone through my Prism Orpheus into my MAC Mini. I see it on the screen. You can see the stability of the signal and all. And I can hear the differences as well.

Here are some of my own observations and hypothesis:

1) Regarding how important platter mass is for speed stability. IMHO you cannot assume a higher platter mass is better independent of drive mechanism. In other words, the platter mass and drive mechanism need to be considered together. Picture a 100 lb platter driven by a wimpy motor. The motor needs to be able to keep the heavy platter spinning at speed. Assuming it can do that, any deviation would be difficult to compensate as the inertia of the platter would work against the wimpy motor.

2) Seems to me, resonance issues aside, the energy of the drive mechanism is much more important. That is why I think high torque motors and flywheels driving platters makes sense. The more powerful the mechanism the easier it is to keep a light or heavy platter moving at speed. Therefore, a TT should be designed with drive mechanism energy and platter weight in mind.

3) My understanding is that AC motors run at constant speed by default, whereas DC motors do not control speed per se but torque. That’s why most DC motor driven TT’s slow down with stylus drag. However, most AC motors, having sufficient drive energy fair better. I suspect that DC motor driven TT’s with large flywheels (e.g. Micro-seiki HS-80 and the Forsell) sound better because the flywheel adds drive energy and compensates for the DC motor instability on its own. Seems to me that a TT with AC motor with high torque or added energy through a flywheel has some advantages to DC motor, with higher motor torque, but without s flywheel.

Just my two cents

Andrew

I would like to qualify my statment above:

"That’s why most DC motor driven TT’s slow down with stylus drag. "

I'm referring to DC-motor drives TT's with an open-loop control system. This means that the actual speed is not compared to the set-point and adjusted for mismatches.

I would also add that TT's using multiple motors closely spaced toghether (e.g., TW Black Knight)help increase the tourqe of the drive system.

Andrew

I have just tried the Fieldpiece SRPM2. It is a laser digital tachometer. It works by pointing a laser at a piece of tape on side of the platter, or any other rotating object in other fields. It purports to have a high level of accuracy and it can be found on Ebay for about $75. I thought this would be an inexpensive device and more accurate than a strobe disk as it goes to three decimal points. The other advantage is that one can play an entire side of an LP while doing the test.

Well, I found it quite disappointing. The reading seemed accurate at first: 33.436. My table speed is finely adjustable so I thought I could just get it to read 33.333 by adjusting the motor controller. Well, I found that the Fieldpiece readings were not repeatable and by just moving the device closer to or further away from the platter, the reading changed, though I know the platter speed remained constant.

So I am going back to the KAB strobe disk which indicates that my table is operating at the correct speed. Perhaps this device is accurate enough for HVAC technicians and people working with motors who need to know RPMs or the total number of rotations from some equipment, but I plan to stick with dedicated tools for turntables. I just can't convince myself to spend the $400 for a Timeline.

Peteayer: "Well, I found that the Fieldpiece readings were not repeatable and by just moving the device closer to or further away from the platter, the reading changed, though I know the platter speed remained constant."

Can't you hold the the tachometer steady or clamp it to something so it would not move?

_______

Yes, and I did. I guess I was not clear enough. I placed the Fieldpiece on a stand and took the reading. I then took a second reading from the exact same spot and they were not the same. I then tried about three different locations each at a slightly different distance from the reflective tape on the platter, and at different angles and these readings also did not match. They varied +/- 1 RPM, ie 33.845, 34.352, 33.908 etc. Each time the device was fixed and never moved. I had the KAB strobe on the platter and it did not waver, so I assume the platter was not changing speed. The stylus was not on a record and I did not adjust the speed on the motor controller.

For such a device to be useful, I would think that any reading from any distance within say 2-5 feet from the platter should be extremely close if not exactly the same. The point is that without getting consistent readings, there is no way of telling exactly how fast the platter is spinning. My conclusion is that for me, this device failed the test.

If anyone would like to buy this mint condition device for perhaps a different use, please contact me.

Dear Peter, I hate to be a pain in the arse, but you wrote, "I found that the Fieldpiece readings were not repeatable and by just moving the device closer to or further away from the platter, the reading changed, though I know the platter speed remained constant." How in fact do you know the platter speed remained constant? I think you are going to say that you know it by virtue of the KAB strobe, but I have been told ad nauseam by others who use both that the Timeline is more sensitive to very small aberrations (like the ones you report) than is the KAB. (I must admit that when I compared a borrowed Timeline to the KAB in my home, using four turntables, I got the same impression.) This says nothing up or down about the Fieldpiece, however. Does the Fieldpiece strobe plug into the wall socket? If so, there could be its Achilles heel. There is a slight variation in AC line frequency, which is why KAB use a battery-powered strobe.

HI Lewm, the Fieldpiece is powered by three AAA batteries. I will accept your proposition that I don't know for sure that the platter remained at a constant speed during the trial. I do know that within the resolving capabilities of my eyes, the numbers on the KAB did not move relative to the leading edge of my headshell which was placed over the numbers when I did that test for a period of 60 seconds.

I also know that I could not repeat a reading using the Fieldpiece when I took separate measurements within 10 seconds of each other. The unit was not hand held, but placed on a platform. The location remained constant (perhaps not precisely the same, but one that seemed to me to be the same). If one reading is 33.845 RPM and the next reading is 34.520 RPM taken from the same location, that is a variation of about 2%, if my math is close. I have confidence that if the platter speed varied by as much 2% within a few rotations, that my eyes would notice that by looking at the KAB. According to the KAB instructions (6.5 drifts per minute = 0.2% too fast or slow), I was easily able to notice a speed variation of 0.2%, 1/10th of the variation indicated by the Fieldpiece. I did not see this variation with the KAB.

I also presume that my ears could detect a speed variation of 2% as indicated by the Fieldpiece. I am able to hear a speed variation of 0.2% (based on the KAB) which was the case with my old turntable. So I agree with you that I can not know that the platter speed is constant with the KAB. But based on my observations of both the KAB and the Fieldpiece and assuming that my math calculations are correct, then I must conclude that my particular Fieldpiece unit is not very accurate, at least relative to the KAB.

I do know someone who has a Timeline. Perhaps I can ask him to bring it the next time he comes by for a listen. We could then do a direct comparison between the Timeline and the Fieldpiece on my turntable. That will tell me something about the Fieldpiece and my turntable. Or, I think he has a DD turntable and I should take the Fieldpiece to him for testing.

After reading the posts, I thought it would be helpful to add my experience with a turntable design that is very unique (at least as far as I know).

I have been working for 4+ years on a turntable design that came to fruition recently. The turntable is a rim drive turntable with a super massive bearing (the largest built, as far as I know) and a massive platter. The theory behind this design was to have very high inertia to overcome stylus drag derived speed variations.

I can tell you with great confidence that the design/theory does work as intended. The high inertia platter/bearing combination brings forth drive and rhythm like no other turntable that I have heard. It is quiet amazing.

That said, the turntable is not perfect, as the rim drive motor speed variations need to be tamed. Speed accuracy is not a problem, but minute variations in speed is an issue for now. I have been working extensively with different rim motor solutions, including rim wheel materials, sizes and durometers. Each has there own sonic signature and pros/cons.

IF the motor speed variations can be tamed, then I believe the current design is unmatched. BUT, I am still seeking a better motor solution that I currently have.

Here is another finding that I came across: if the table has a stable the motor speed and has the ability to rip thru transients and not be adversely impacted by stylus drag, then you will discover that your next culprit is eccentric record centers. Wow/flutter derived from eccentricity in the LP will become more apparent/audible.

This is just an FYI and thought it might help in your thinking.

I agree with Banpuku about hearing the effects of record centre eccenticities.
On mt Victor TT 101 DD turntable.....which demonstrates admirable speed accuracy via the Timeline.....I am more aware of this phenomenon on certain records than I am when using the Raven AC-2 belt-drive.

I guess in the best of all possible worlds, your turntable's speed irregularity would combine with your LPs off-center spindle hole to give you perfect pitch.

Thanks, Peter, for your further description.

Banpuku, Have you looked at the TT Weights rim drive or the Trans-fi Salvation rim drive? Each has its strong advocates. Both seem to ascribe to the heavy platter/rim drive paradigm. I have not heard either, but I note that both seem to use a rather small diameter wheel to drive the huge platter(s). On the other hand, the VPI and Teres rim drive(s) use a rather larger diameter drive wheel. Where do you come down on this design choice? No doubt you've given that a lot of thought. Just off the top of my head, I would have thought that the larger the circumference of the drive wheel, the better, right up to where the diameter of the drive wheel would equal that of the platter.

Lewm ~ I have the TTWeights rim drive and the Timeline shows it does not have speed stability, this on 2 different TTWeights rim drive models. Does it sound OK? Yes but when I now listen to a DD table I can clearly hear the difference.
(dealer disclaimer)

Dear Skos, You are preaching to the converted. I am a confirmed DD junkie. I still do like my highly modified Lenco, however. I was unable to test it with the Timeline, because the spindle hole in the Timeline is too small to admit the spindle of a Lenco (or of my Kenwood L07D). This to me is a major oversight in the design of the Timeline, as I think it would have been easy to supply alternative spindle hole pieces for it, especially at the price. (I could imagine a removable rim-threaded bottom puck; three such pucks could accommodate all typical spindle diameters, with a snug fit.)

I think I remember your earlier posts on the TT Weights. It appears that their drive wheel and the rim of the platter have been re-engineered in their latest models or their revised older models. Perhaps those issues were resolved.

Lewn ~ a customer of mine has the TTWeights upgraded player with the new extended rim and still the Timeline showed it was unstable. Can he hear it? No but it didn't make him fell all warm and fuzzy.

God never meant for audiophiles to have a warm and fuzzy moment. If an audiophile is not worried at any given moment, he is compelled to search for something to worry about. Enter, the Timeline.

I notice very few, if anyone, is using a test tone and measuring frequency, as a means of setting TT speed. My limited experience is that the KAB disc is pretty insensitive, I have an AC motor and so the KAB disc shows perfect speed, however the 3150 test tone measured with the Feickert App, shows fluctuations of up to 5 Hz from a mean of 3150, after I have adjusted the power supply. The test tone takes stylus drag into account. So what are the issues with this method?

So what are the issues with this method?

I kept hopping someone else would chime in. I have the Feickert App and the Feickert LP but also have the new Quality LP from Chad (Ultimate Analog Test LP, track 10) that both work with Fozgometer.

Test result is different with each test record and I don't want to get into multiple page (guessing game) explanation as to why.

The Timeline shows what's happening very easily and quickly with minimal hassle. I'll continue to test but the results with iPhone are dubious.

Clarification of my post (above).

I bought the Ultimate Analog Test LP for the Fozgometer and found track 10 worked with the Feickert iPhone App.

Both it and Feickert test disc have the steady state 3150 HZ test tone.

I have checked my VOM with the Rives test CD and it reads +_ 1 hz at frequescies from 1000 to 3150 hz, so I think I will buy the Ultimate Analog Test LP to cross-check my strobe disk. I also happen to have an old dual trace scope, so I should also be able to set azimuth from the same diak. No often I can "kill 2 birds" with $40.

SME30/12

Here is a video of the SME 30/12 with the Sutherland TimeLine. The only other videos that I have seen with the TimeLine are Halcro's Victor TT and the Sutherland website.

Hi Peter,
Excellent. First, that is a really long tonearm. I'm not envious, just impressed. I noticed just a slight amount of drift over the 5.2 minutes of the song. It appears the speed is just a little fast by about 1.6%. I estimated that the line drifted about 1 inch over the 5.2 minutes and I also estimated the radius from the timeline center to the album cover to be 10 inches. So, if I did the math right, the angle changed 5.7 degrees over 5.2 minutes. If you have exact numbers then the calculations would be more meaningful. That means the number of record rotations was off just 2.8 rotations out of 173.33 rotations. Are you able to adjust the speed a bit? At the end it seemed like the line did not shift when you lifted the tonearm. Is that what you saw? Is your speed controller closed loop? When you dropped the tonearm onto the record did you see any shift in the line?

Hello Tony, You are correct in observing the slight drift to the left over the length of the video. I just measured the relevant distances and they are: drift from right edge of "Philips" label to center of label is 1/2" (0.5"). The distance from the spindle to the laser slash line is 13.5". That should change your calculations slightly.

The SME motor controller has incremental settings of, I believe, 0.1%. I can't remember where I read that though. The line does move slightly when lifting the stylus out of the groove. Halcros Victor TT video is very impressive in this regard. The SME belt drive table should be set for correct speed while playing an LP to account for stylus drag.

You are most observant to catch the slight drift to the left, which means the table is very slightly too slow. I can not hear this. A close examination of Halcro's DD Victor video also reveals a slight drift to the left of about the same 1/2". Note the laser dash is centered on the blue tack and by the end of the 4 minute video, it is just barely touching the blue tack as it has drifted to the left. This video has been held up as the gold standard reference for DD turntable speed accuracy. I have found no others on the net except the Sutherland website videos in which none of the turntables hold correct speed.

In the interest of collecting data on different turntable performance, and learning in the process, I borrowed Albert Porter's TimeLine and decided to share the results.

I'd be very interested in seeing your calculations and translating them into the actual speed, ie. 33.4 or so RPM. Thanks.

Hi Peter,

I updated my calculations and also found an error. My previous calcs were off by 100 because I had calculated a % and then used that for an absolute. The correct numbers now with your measurements are speed is fast by 0.003%. The 5.2 minutes of playing time were off by 0.0059 rotations out of 173.33. (That 100 makes a big diff in the numbers). Drift to the left means slow? Ok, I see that now too.

Thank you Tony. So, if I understand you correctly, my table is slow by roughly 6/1000th of a rotation out of 173 rotations or 0.0000346 per rotation. Said another way, 0.003% slow is 0.00003 RPM slow. So my table in this video is running at 33.3333333-0.00003 = 33.333303 RPM. Is that correct?

The precision of the Sutherland TimeLine is such that is can clearly show this deviation. I'm sure that SME and most other designers do not use such fine measuring tools when testing the results of their designs. I've mentioned elsewhere that my turntable shows correct speed while using both the KAB strobe and the paper disk supplied with the turntable.

I am perfectly satisfied with setting the speed with the KAB. But this experiment with the TimeLine has been very informative. The motor controller increments are course enough to be detected by the TimeLine. I've tested the number of increments I can hear, and it is somewhere between 4-5, either too fast or too slow. I can not detect by listening a variation of 1-3 increments on the motor controller in either direction. Perhaps others with perfect pitch could hear this.

The new TechDas turntable has "passed the TimeLine test." It would be interesting to see that video and the video results of other tables which have different drive types using a similar methodology to my and Halcro's test.
I have heard of some tables showing even better results, but without video documentation.

Hi Peter,
Sorry for the confusion this morning. I was rushing because we were preparing to go to a wedding. I was excited to see your post and wanted to reply before we left and my wife was bugging me to get off the computer and get ready to go.

The drift is 0.4 degrees/minute or 0.001133 revs/min. So after 5.2 minutes, the total error was 0.00589 revolutions out of 173.33 total revolutions. That is a speed error of just 0.003%. It may not be 0 as some DD turntables claim to be; but it is pretty close.

Your turntable is absolutely perfect. Its speed control is on the order of any type of drive system, ie. direct drive, rim drive, etc. in terms of accuracy. The only other check would be with a scope to see the constancy of speed over a single revolution (Wow and Flutter); but I'm sure it is laboratory grade as well. I wonder why the Timeline device does not flash more often. If it did, it would give some indication of speed variation during one revolution.

Thanks for sharing.

Hi Tony,

The TimeLine device that I borrowed from Albert Porter is the older model. The new/current one has, I think, six strobe lights/flashes spread equidistant around its perimeter. I know it is different in some meaningful way.

It would also be interesting if the duration of the strobe itself would be quicker on and off. Then the strobe slash or line on the wall would be of shorter length. As it is now, because the device is rotating on the platter, the length of time that the light is on smears what would be a dot into what appears to be a line. This is consistent with my observation that the further away the wall is from the spindle, the longer is the strobe line/slash.

It is an incredibly interesting device and I think one could study what happens to the line with a slow speed camera and thus detect different behavior between belt drive and DD tables during the moment of flash, i.e. during very short durations, and perhaps detect visually deviations of speed consistency. Some listeners claim to hear this earlier in this thread.

If you look closely at Halcro's video, the strobe line looks different than it does on my video and the quality of my line changes slightly during the course of my video. So something else is going on.

As was mentioned earlier in this thread, there is also a distinction to be made between speed accuracy and speed consistency. I agree with those who think the latter is more easily heard.

Peter,
Having extra flashes would not necessarily be more accurate or enable small period variations to be seen. That would depend on the indexing accuracy of the machine used to make the multi flash Timeline. A typical Rotary Head might be a factor of 10 less accurate than the performance of your deck in percentage terms as shown above, and certainly less than the clock in the Timeline.

John
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I am hoping to establish a video database of various turntable speed test results. The thread is over on WhatsBestForum. Here is a link:

http://www.whatsbestforum.com/showthread.php?13137-Turntable-Speed-What-matters&p=239164#post239164

So far, I've only posted Halcro's excellent Victor T101 video and my own video of the SME 30/12. Perhaps in time, there will be more turntables added. If anyone wants to upload such videos to YouTube, I will gladly add those links to the WBF thread in a list in post #1.

I really enjoy reading about this topic!. as most of us have been through many different TT combinations etc.. think its possible to come up with a workable compromise..

I did post up a video but some people had a laugh at it as i have no idea why but it clearly showed with a hi quality strobe that groove modulations and my finger did not pose a problem for this fantastic turntable...let me tell you i put a fair amount of pressure much more then 20 tonearms!

The table is the Pioneer pl L1000A.... quiet as its kept, it has some of the best electronics for controlling the hung rotor motor! If i had a timeline or equivalent i would post up a video but i do not ...anyone want to borrow one?

Lawrence
Fidelity_Forward