Turntable Speed Precision

Phelonious Ponk

New Member
Jun 30, 2010
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TTWeights GEM rim drive. I don't have Revolver, but I am listening to Yellow Submarine. :D

View attachment 4958

You need to buy revolver. And Rubber Soul. The English version. Opens with Drive My Car. As it should be. Unless we want to devolve from drive speed to drive my car to " Beatles or Stones?"

The answer, by the way, is yes. Always has been.

Tim
 

DonH50

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Jun 22, 2010
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Does the app truly measure TT speed, or is it influenced by off-center records that can cause similar variations in the output? I don't know, just curious.

How much pitch variation is detectable varies from person to person. 1 Hz is not detectable by most of us; musicians (raises hand) are a little more sensitive (because we have to be) but still I'd guess 1 Hz at 1 kHz is barely detectable if at all. We use cents, not Hz, for determining pitch variation as it varies with frequency as well. See e.g. http://en.wikipedia.org/wiki/Cent_(music) .


HTH - Don
 

Bill Hart

Well-Known Member
May 11, 2012
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Two questions: first, if speed variation is caused by line voltage fluctuations, or some other shortcoming in the TT/controller design, the solution is really changing out the TT or motor controller, not 'adjusting' it for speed, since the primary cause of variations with remain, irrespective of adjustment, right?
Tim- what exactly is it we are to listen for on those old Beatles records?
I'm pretty sensitive to pitch variations, and out of tune instruments- I also thought the general rule was to tune flat rather than sharp, because it was less noticeable on guitars. (And, at least re guitars, isn't it impossible for the instrument to really be in tune at all of the same notes on the neck- i can't remember why this is so, but since you know guitars, you could probably explain- i seem to remember that tuning is at best a compromise).
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
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Hi

I sincerely would like someone to start a thread on what makes a good turntable .. heck! I will start one and expect the experts to chime in ...
 

audioarcher

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May 6, 2012
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Frantz, I would love to hear some expert opinions on what makes a good turntable as well. The problem is they can only say so much without giving away secrets to the competition. All they can really say is how they feel about a given approach. Doubtful they will go into to much detail about how they implement it.

I'm not a designer but have played around with different belt materials and motors on one of my previous TT's. I found that the more stretchy a belt is the more it smears the sound. When I tried a different motor capable of using mylar tape the sound was more transparent and less smeared. Mylar tape stretches much less than rubber belts. With the mylar tape speed differences were more noticeable though. With my current DD turntable I get the same clarity without any noticeable speed variations. So after speed and stability are sorted out vibration control is another priority. What the turntable is made out of, how its put together and what it sits on will affect how low its noise floor is. Also the materials used in construction can affect tonal balance. A TT design has to juggle all these things. If all these things are implemented well and in a balanced manner the result will be a great TT IMO.

Sean
 

rbbert

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Dec 12, 2010
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No one directly answered the question about how much (quantitatively) speed change/error is audible. There are good summaries (referenced) in Wikipedia about this for those more interested. I can recount my own pretty extensive experience (which agrees with that of others I know of personally). Briefly, on most music (as opposed to noise or test tones) an error of 0.3% (5 cents, or 5 percent of a semi-tone) is audible by most people when the two are directly compared. A musician with perfect pitch or even a very good ear is likely to notice a difference as small as 0.1% when trying to play along with a tuned instrument.
 

Bill Hart

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May 11, 2012
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How about it guys?
I gave it a try, i didn't have a pure test tone at 3150, but a band with white noise at that frequency. There was some fluctuation- i'll see if I can't capture an image of the reading on my iPad when I have a chance. I assumed some of this was due to the fact that white noise really isn't at just one frequency, is it?
 

jtinn

Industry Expert
Apr 20, 2010
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Maybe some of our fellow analog fans can post their results using Platterspeed. All it takes is an iPhone/iPad, the app, and a 3150 test tone (available as track 10/side 1 on the Analog Productions test record).

Unfortunately this is not accurate. There are too many outside influences that effect the results; distance and placement, external noise, etc.
 

amirm

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Apr 2, 2010
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No one directly answered the question about how much (quantitatively) speed change/error is audible. There are good summaries (referenced) in Wikipedia about this for those more interested. I can recount my own pretty extensive experience (which agrees with that of others I know of personally). Briefly, on most music (as opposed to noise or test tones) an error of 0.3% (5 cents, or 5 percent of a semi-tone) is audible by most people when the two are directly compared. A musician with perfect pitch or even a very good ear is likely to notice a difference as small as 0.1% when trying to play along with a tuned instrument.
I can provide part of the answer as I had to dig it up for another argument :). Perceptual research/listening tests shows an interesting curve when it comes to low frequency/speed fluctuations:



We see that there is a peak at 4 Hz and sensitivity then drops quickly on either side (presumably due our desire to better understand speech which has similar repetitions). So to determine audibility we need the spectrum of the change. In other words, a single number of deviation in speed is no sufficient. We need to know the frequency with which it changes. 1% deviation at 1 Hz may be less audible than .5% at 4 Hz.
 

catastrofe

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Feb 17, 2012
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Unfortunately this is not accurate. There are too many outside influences that effect the results; distance and placement, external noise, etc.

That's an interesting comment. Can you elaborate? Chris Feickert is pretty well respected, and it's difficult to understand how he could put something out there as a measurement tool that isn't accurate.
 

Mosin

[Industry Expert]
Mar 11, 2012
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Hi

I sincerely would like someone to start a thread on what makes a good turntable .. heck! I will start one and expect the experts to chime in ...

When I first decided to get into audio manufacturing, I asked for advice from some trusted guys. One sent me a rather long e-mail that I saved. Here's a part that I'll share...


"...A couple hints- there are almost no true professionals in home audio, regardless of the stature, size of their businesses, or supposed qualifications. Acceptance & success is as much or more who you know as what you have to offer. Watch your backside..."

I have tried to use that e-mail as a business model, and it has worked well, except when I didn't listen to the little bell ringing in my head regarding the last piece of advice he wrote. Hey, we all learn some things the hard way, right? ;) So, there are no experts, and there are some lowlifes out there, but I don't mind posting some of my basic philosophies, not that I expect total agreement from everyone.

I believe there are some rules to follow, regardless of any technical approach taken.

1) A turntable should be user friendly.
2) It should actually work without undue failures.
3) Whoever made it should back it up, if it does break.
4) It should spin quietly at the proper speed, or at least at a speed accuracy that reflects its purchase price.
5) Setup shouldn't be a dramatic undertaking. It should be straightforward.
6) Once set up, it should stay that way.
7) Maintenance should be extremely minimal, if at all.
8) It should attractively fit in any room with any system.
9) Every part should have a purpose for its existence because a turntable is a lot like the audio chain itself. It is only as strong as its weakest link.
10) It should pass WAF with flying colors. If Mama doesn't like it, it almost isn't worth the grief of ownership for a lot of guys.

Skinning the cat:

There are three drive systems commonly in use these days: direct, belt and idler. There are also endless arguments about which one is best, usually by those who are either biased because of what they happen to own, or by those who haven't actually been exposed to better units of each of the drive types. My experience tells me that units at the top of the food chain can sound a lot alike, depending on the intentions of the designer. Of course, I have my favorites, and they all have an overall sound that is at least somewhat similar to that of my turntable. Wait... Aren't we striving for a neutral presentation, and shouldn't that be every designer's goal? Well, define neutral. Also, realize that every recording engineer who masters a record has to use his judgement when practicing his craft. I believe we have a representation at the end of the day, and he who declares his to be neutral is either terribly misguided, or trying to misguide others. If that was not the case, all our systems would be identical, and we wouldn't need this forum. For me, that's the starting point.

Now that you know my fundamental views, I'll give my opinion concerning speed accuracy and my way of getting there. If someone wants to start that thread, I'll go deeper into my ideas of what I believe makes a good turntable.

No matter how you slice it, speed accuracy is somewhat dependent upon cost. You can't get there for peanuts. So, what do you need?

1) A decent motor is a given. That sounds simple enough, but it is the biggest hurdle to jump when acquiring parts. One really big manufacturer uses a motor that can be bought for around $56...at least that is what a sample costs. I know because we bought six of them at different times for testing. They all had shaft inconsistencies, and they all cogged like no tomorrow. They are very reliable, however. What does that tell you about that manufacturer? A lot of guys use an off-the-shelf motor that is very consistent between samples, but they have a failure rate that is higher than I like. It is an easy replacement, however. Most of those guys stand behind their product, so it is a minor inconvenience. Other guys have motors custom built for them. Those are generally really, really good, but not always because it costs a lot to repeat that exercise when the results aren't dead on. Sometimes, close enough has to suffice. I use a tried-and-true three-phase motor that is insanely expensive to implement in a turntable application, but the payoff is worth the effort to me.

Here's what I like to see from a properly applied motor...



...but will it do it at every speed when under a real world load? I define every speed as any possible setting. Ex: 33.33333334, 33.33334333, etc., etc. Why should anyone care? Some people care because they can hear a one/fifth harmonic, and some can even hear the direction of wire. Also, not all records were recorded at the same pitch, and people who want the best need a way to compensate for that. Some designers try to give the user the flexibility to adjust the speed closely. I know I do. In fact, I may go overboard by offering 200 steps per cycle. My motor changes speed by changing frequency, so I have a microprocessor programmed to handle that. I am paying to have it coded anyway, so the extra adjustment steps aren't a big cost hit. The cost is in regenerating three synchronized AC phases. At the end of the day, I have a stable, but expensive solution. It's one way to skin the cat.

2) As important as a decent motor, is good system inertia. If a platter/bearing design doesn't take into account how inertia is handled, it will fail to maximize the performance of any motor. If the mass is in the wrong place, or just plain wrong, speed can be negatively affected, regardless of the expense of the motor and all its trimmings. This aspect is harder to achieve than getting the motor right because it is hard for a designer to wrap his head around the concept. As a result, a lot of guys design a platter for sex appeal, rather than for sheer performance. They seem to operate by the "whatever is cool" method. The reality of it is that physics come into play whether it is realized by the maker, or not. That's one reason why some turntables with fancy controllers still sound like crap. Some guys do the math, though. They plan the dynamic mass, static mass, spindle drag and everything else that goes into determining the inertia involved. As a result, their turntables don't jitter, lack micro dynamics, or exhibit the effects of stylus drag, etc. They just sound good.

Summary: In my opinion, that's what makes great turntable speed precision. It takes good design decisions for both aspects to get the best result possible. Skip one, and the overall goal suffers immeasurably.


Caveat: You may disagree, and your mileage may vary. I remain totally convinced, however.
 
Last edited:

Johnny Vinyl

Member Sponsor & WBF Founding Member
May 16, 2010
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Just found this thread. What an interesting read, but I'm a bit surprised with all of the analog fans here that it seems to have died. Several members have already indicated they'd love to see a separate thread , and Win has offered to share his thoughts even more than what he already has.
 

astrotoy

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May 24, 2010
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I also just found the thread. I have been measuring the speed and speed stability of my TT for about 3 years, during my major vinyl ripping project (over 3000 LPs so far). For each LP I measuring the speed and speed stability using a Monarch PT99 meter which comes with a strip of reflective tape which one adheres a small section on the side of the TT and, bracing the meter, it can read the speed to 3 decimal places, i.e. 33.333. It is less accurate than that, but I can reliably get measurements to 2 decimal places - 33.33. My TT (VPI HRx with rim drive) can be adjusted with the VPI SDS box, which allows me to change the frequency of the line current. I can move the speed reliably from 33.34 to 33.33. My TT varies about .01 rpm from one revolution to another, about .0002, perhaps 5 times better than 1 in 1000 mentioned near the top of the thread. I first bought a similar meter from Audio Advisors or Music Direct, but it only measures to 1 decimal place, i.e. 33.3. So I cannot see variations within that decimal place. VPI claims in its ads that the rim drive is rock steady. At the hundredths place that is not true, but with the typical meters, I don't think you can see any issue. I certainly cannot hear any wobbling. The Monarch PT99 is less than $200 which is not much more than the meters sold by the hi-fi shops. It is an industrial meter, not a hi-fi accessory. It also allows me to measure the speed of the TT at any time - and with any record - not like having a strobe disk or a test record.

I have found that the speed slowly varies during the day, a temperature effect, causing the distance between the rim drive and the platter to vary slightly. Since I adjust the speed with each record, I can compensate for the changes and have every record ripped or played at its correct (within .0002) speed.

Larry
 

MylesBAstor

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Apr 20, 2010
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I also just found the thread. I have been measuring the speed and speed stability of my TT for about 3 years, during my major vinyl ripping project (over 3000 LPs so far). For each LP I measuring the speed and speed stability using a Monarch PT99 meter which comes with a strip of reflective tape which one adheres a small section on the side of the TT and, bracing the meter, it can read the speed to 3 decimal places, i.e. 33.333. It is less accurate than that, but I can reliably get measurements to 2 decimal places - 33.33. My TT (VPI HRx with rim drive) can be adjusted with the VPI SDS box, which allows me to change the frequency of the line current. I can move the speed reliably from 33.34 to 33.33. My TT varies about .01 rpm from one revolution to another, about .0002, perhaps 5 times better than 1 in 1000 mentioned near the top of the thread. I first bought a similar meter from Audio Advisors or Music Direct, but it only measures to 1 decimal place, i.e. 33.3. So I cannot see variations within that decimal place. VPI claims in its ads that the rim drive is rock steady. At the hundredths place that is not true, but with the typical meters, I don't think you can see any issue. I certainly cannot hear any wobbling. The Monarch PT99 is less than $200 which is not much more than the meters sold by the hi-fi shops. It is an industrial meter, not a hi-fi accessory. It also allows me to measure the speed of the TT at any time - and with any record - not like having a strobe disk or a test record.

I have found that the speed slowly varies during the day, a temperature effect, causing the distance between the rim drive and the platter to vary slightly. Since I adjust the speed with each record, I can compensate for the changes and have every record ripped or played at its correct (within .0002) speed.

Larry

I think the Monarch is the same thing as the Digistrobo save that you get one more decimal point (mine goes to 33.3). And I agree that it's the way to go. I have a friend who mounted his Digistrobo next to the turntable so he can check the turntable speed anytime.
 

HK Panda

Well-Known Member
Nov 28, 2012
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There is an interesting paper authored by Teres audio, which they are using to promote their motor technology.

According to the article "rotational speed that is sufficiently stable to prevent audible degradation of reproduced sound. Close examination of speed stability reveals a host of problems. Micro (short duration) speed variations are responsible for audible problems that most audiophiles would not attribute to the turntable drive mechanism. Harshness, muddiness and smearing are the classic symptoms of micro speed variations. In addition problems with a slow, dull presentation can often be traced to deficits in the turntable's drive mechanism.
Human hearing is remarkably sensitive to infinitesimally small errors in the time domain. This has been well documented in digital audio where timing errors (jitter) as small as ten trillionths of a second, have been shown to be detrimental to quality sound reproduction."

I don't own a Teres product, but I found the subject matter relevant to the topic discussed here.

http://www.teresaudio.com/manuals/teres_speed_tech.pdf

No Disc
 

jtinn

Industry Expert
Apr 20, 2010
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483
Maybe some of our fellow analog fans can post their results using Platterspeed. All it takes is an iPhone/iPad, the app, and a 3150 test tone (available as track 10/side 1 on the Analog Productions test record).

There is a lot more to it. The room has a lot to do with it as does the volume (db), placement of the iPhone, placement of the tables, etc. It really is not reliable unless multiple tables are measured in a very controlled environment and conditions and then only those tables can be compared.
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
Sep 6, 2010
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There is a lot more to it. The room has a lot to do with it as does the volume (db), placement of the iPhone, placement of the tables, etc. It really is not reliable unless multiple tables are measured in a very controlled environment and conditions and then only those tables can be compared.

Jonathan, that's the second time you've said this on this thread. Why do you not think that the app is reliable? How can room, volume, placement of the iPhone, placement of the table affect the frequency detection of 3150Hz?
 

jtinn

Industry Expert
Apr 20, 2010
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Jonathan, that's the second time you've said this on this thread. Why do you not think that the app is reliable? How can room, volume, placement of the iPhone, placement of the table affect the frequency detection of 3150Hz?

I did not see your question until today. I will try to be more specific.

All measurements should be made in the same conditions to eliminate outside variable influence. If they are not, one must use a validated test method that quantifies and accounts for those factors. If you do not, the tool is a nice estimator of performance, but really doesn't mean much, especially when measuring at the low end of its sensitivity.

To demonstrate this, simply have your Apple device play the program's test tone from its own speakers and record that. You will see that the recorded wave form is pretty messy and not at all one frequency. In fact, the level of variation is exactly what the best turntables produce themselves. We know that the DAC that drives the apple speaker is doing the best it can to command exactly 3150Hz, but in fact, the mic is measuring something on the same scale as good turn tables put out. Thus, if you believe you have a measurement that is in this range take it with a serious grain of salt since the apple hardware/software's own accuracy is at its measurement limits of a good turntable's output with a tone record. See the attached pictures of a representative recording.

Platterspeed.jpg

Platterspeed2.jpg

The Platterspeed app is great to make sure your system, as quantified by your phone/iPad, is not changing or for comparing two side by side turntables, in identical conditions. Be careful beyond that when making calls about superiority when the measurement is at the same scale as the iPad's measurement of its own 3150Hz test tone.
 

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