Turntable speed accuracy

No one seems to set the speed as I do. I adjust speed while playing same known track on CD as well as TT. I measure with stopwatch and play simultaneously going back and forth such that the song start and ends at exactly the same time on both CD and TT. I change source back and forth, each note sounding exactly same that you can hardly tell diff. It helps that my main CD source and TT are set pretty much to same tonal balance. It takes few iterations, but then I listen without worrying about speed. Makes sense?

Palasr wrote: "While frequency accuracy (and adjustablity) is one issue, it doesn't begin to address waveform shape, harmonic distortion, phase amplitude and shift, and all the other interesting things that go into generating a waveform suitable for driving a synchronous AC motor."

I have a Mark Kelly AC-1 drive controller on my VPI TNT that features separate manipulation of several of these parameters, while deriving an AC waveform from a 12V battery independent of the power grid. Unlike a VPI SDS, the AC-1 is a true two-phase controller-- it eliminates the phasing capacitor from the motor tower. Varying the separate effects independent of frequency is easily audible, as are differences between belts of varying compliance-- yet the strobe disk doesn't move a whit.

when i compare various turntables to the same recording on my Studer A820 it's easy to hear which turntables get the closest to matching the soliditiy of the music on the Studer.

Nojima Plays Listz is a very good recording of Piano on Lp, and is a Tape Project tape too; in theory the solidity and speed accuracy of that tape is the reference for the Lp as we know it's the actual source. on that recording there is no place to hide any speed variations as well as inaccuracies. and there are plenty of peaks to hear also.

i do have the KAB strobe and use it. however, it's limitation is the accuracy of the printed strobe and the perfection of the center hole of the strobe.

i think the tape-Lp comparison has more value to me.

Your 60Hz line freq, may no longer be sacred! This COULD POSSIBLY become an issue soon. A copy/paste, from a previous thread: Something that got me thinking more about speed accuracy lately, as both of my tables are equipped with AC synchronous motors: (http://wattsupwiththat.com/2011/06/25/it-hertz-when-you-do-that-power-grid-to-stop-regulating-60-hz-frequency/) (http://radiomagonline.com/infrastructure/power/60hz-stability-going-away-0627/) If you are using a strobe disc, that depends on your house lighting's 60Hz flicker, or your table has a motor, dependent on your AC's 60Hz for speed regulation; take note. This may soon become a concern. (Note: They were NOT simply referring to the nightime correction, in these articles)

My Dual turntable has a built in AC light bulb to check the strobe marks on the platter rim. It drifts over time while the KAB strobe light is stationary. So there is a discrepancy between using AC line frequency and quartz locked frequency. Jeez, I am such a KAB sucker.

From the Dual manual:
"It can happen that the stroboscope lines appear to move slightly although the exact speed setting with stroboscope lines stationary has not been altered. This apparent contradiction is explained by the fact that the electronic central drive motor operates fully independently of the line frequency whilst the only relatively accurate line freqency of the AC current supply is used for speed measurement with the light stroboscope."

I am happy that some people found their perfect turntable without worrying about these things. Us neurotics just have to suffer.

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When I am playing Vladimir Horowitz on my turntable should I ask him to stop on the half hour Eastern Standard Time so I dont have to listen to the speed corrections ?

Seriously though when I was selling Elite Rock Townsend turntables which used an AC motor, when I corrected the operating voltages from 69.9 to 70 volts, even though AC motors are supposedly dependent of frequency not voltage, the sonic presentation changed from that of a Van den Hul to a Koetsu without changing the cartridge. Something was going on - motor resonance, optimum torque, minute speed changes - who knows.

Atmosphere is right there are many things we hear that are not measurable.

A sinewave doesn't tell you whether the pianist was happy or sad when they hit the note.

By the way the 0.02 is the correction of the AVERAGE fequency deviation - that is quite different from the real deviations in frequency.

My last post should end this thread.

The VPI SDS adjustment, a strobe and light bulb, or a $100 KAB strobe, "are all" about as accurate as your AC line frequency!

How do all you "SUCKERS" feel, that payed $100 for the KAB BS!

AC line frequency in the US is adjusted within .02% and accurate within .033%, the KAB strobe is accurate within .03%.

AC from the power line is as accurate. The KAB website info is WRONG! A light bulb and strobe disk is as accurate. END OF STORY!!!

From Wikipedia

Regulation of power system frequency for timekeeping accuracy was not commonplace until after 1926 and the invention of the electric clock driven by a synchronous motor. Network operators will regulate the daily average frequency so that clocks stay within a few seconds of correct time. In practice the nominal frequency is raised or lowered by a specific percentage to maintain synchronization. Over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million.[19] In the synchronous grid of Continental Europe, the deviation between network phase time and UTC (based on International Atomic Time) is calculated at 08:00 each day in a control center in Switzerland, and the target frequency is then adjusted by up to ±0.01 Hz (±0.02%) from 50 Hz as needed, to ensure a long-term frequency average of exactly 24×3600×50 cycles per day is maintained.[20] In North America, whenever the error exceeds 10 seconds for the east, 3 seconds for Texas, or 2 seconds for the west, a correction of ±0.02 Hz (0.033%) is applied. Time error corrections start and end either on the hour or on the half hour.[21][22]

All I know is that the wavering on the decaying note of a piano is REALLY annoying and that usually happens on belt-drive suspended turntables with stretchy belt. I may not know what I like but I know what I don't like.

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In absolute terms there is no such thing as perfect speed stability. There is always a finite amount of instability. It's like saying a surface is smooth. A smooth surface looks like a mountain range under a microscope.

So the right question is what level of speed instability is audible? It is a fact that uneven drag from a stylus will affect platter speed. But is it enough to be audible?

To the novice it would seem that a good motor and a heavy platter will push instability into the in-audible range. Early work with digital encoding fell into the same trap. Who would have imagined that infinitesimally small timing errors in the tens of pico seconds would be audible. Well, it is clearly documented fact that these microscopic errors are audible. This tells us that our ears are far more sensitive to errors in the time domain than anyone would have imagined.

In my opinion achieving speed stability such that there are no audible artifacts is something that state of the art turntables approach but never quite meet. My experience has shown that there is always room for improvement when it comes to speed stability.

Peterayer alludes to interesting questions:

Is speed stability THE most important turntable parameter?

Is there a degree of speed stability below which variations become inaudible?

Is this something that could be tested with reproducible results?

How does a turntable's immunity to outside vibration and ability to dissipate internally generated noise and vibration impact performance relative to speed stability?

I recently bought a Vibraplane isolation platform for under my turntable. It replaced the Townshend Seismic Sink which I then put under my SME motor controller. Isolating the motor controller from vibrations made a remarkable change to the sound of the system.

I understand why isolation under the tt would improve the sound, but I was surprised by the improvement under the motor controller. Could someone explain to me what is going on there?

Also, does anyone have any experience with replacing the rubber belt with a thread on an SME table? Thanks.

Hiho

The drive system on the TW Raven just is not perfect, that's all.

Does the TW raven have any "measurable" wow and flutter, or rumble?

The VPI TNT III and IV with SDS and their motor, flyweel, and belt system have "UNMEASURABLE" wow and flutter and rumble. The accuracy and consistency, is better than "ANY" tape deck or disk cutter. That is "ALL" that is necessary or maters! VPI has not improved since, or has anyone else as far as speed, end of story! Do not worry or leave sleep over this.

The strobe lines on a strobe disk are not "exactly" spaced, and the flashing bulb has ever so slight time delays, which leads to a very slight jitter of the image.

As far as the KAB strobe goes, I agree it is a better way of measuring speed inconsistencies, that "only mater" to neurotic audiophiles! Sane, intelligent, knowledgeable people just do not need it!

You and Moncrief are splitting hairs here, and hung up on "unaudible absolutes"!

How many years was it before side one of Kind of blue was found to be 1/3 of a semitone fast? Maybe Miles knew, but who else? Speed variation "is" noticeable on classical piano "IF" you have played a piano, but typically the audience could care less.

I have read the IAR and Moncrief is a very good "theoretical" technical BSer. You should read his BS about "audible goodness curves", or the Oracle having 377 times lower distortion than a Linn, or his "Wonder" caps. He can weave a technical tale as good as anyone, but he is no Richard Heyser!

I haven't got perfect pitch and my friends tell me my timing aint that good, but I find piano recordings fantastic for laying bare speed and VTA issues. The words clangy and compressed come to mind when things aren't well, assuming the recording is ok to start with.
Regenerated ac supplies are quite cheap and accessible today and possibly an easy upgrade for tt's with simple supplies.
Love the US$6000 VPI Classic III - Fremer says its one of the most speed stable belt drives he has heard - the supply consists of 1 cap and 1 resistor. Be interesting to run the timeline on one.

Speed accuracy is important for me since I jam with guitar while record is playing and that's one of my ways to realize how precise the speed is. If it's faster or slower by small fraction of rpm I'll hear the difference in tunes.

Don_c55: "Just buy a strobe disc and illuminate it with a light bulb. The 60 Hz AC frequency does not fluctuate enough to worry over."

I wish that's true but using your method and comparing to a KAB strobe, there is a noticeable visual difference, even when your turntable is accurate the light bulb frequency will drift and you end up adjusting to the wrong speed.

Not only the speed should be accurate but, more importantly, no wavering or no intermittent irregularity. To me cogging or analog jitter has the worst effect on the sound of playing a record. DD gets the speed accurate but often suffers from motor cogging. When done right then DD sounds great. Belt is good at filtering the jitters but the elasticity on the belt creates another set of problem. Sigh, what a circle jerk of a hobby!

Don_c55: "If your platter is heavy, playing a record will not affect the speed."

Didn't Halcro just said he tested the TimeLine on the TW Raven, which has a heavy platter?


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Below is an excerpt from the long winded and thought provoking piece that Lewm and Halcro was referring to in the below analogy. Good read, if you have time. :-)

Peter Moncrieff in International Audio Review, issue # 80:
Consider the following analogy. Imagine first that you want to draw a music waveform, like the ones you've seen in previous IAR articles. Draw it on a square piece of graph paper. Note that you can freely move your hand in two dimensions on the graph paper, so you can simultaneously draw both the varying amplitude (height) and progressing time (horizontal axis) of the waveform on the graph paper. Next, imagine that you're doing the same thing, but you've turned the piece of graph paper sideways, so that your wrist moves from side to side (instead of up and down) as you're charting the waveform's amplitude variations.

Now, imagine that you can only move your wrist from side to side, and can't move your hand up and down at all. Your hand holding the drawing stylus has now become just like a phono cartridge holding a stylus that can only read the side to side variations in a record groove. Your hand holding the waveform drawing stylus is mounted on your arm, the same way that a cartridge holding the waveform reading stylus is mounted on the pickup arm of the record player.

If you were to try drawing a music waveform, while limiting your hand to only this side to side motion, you couldn't do it. There would have to be a further mechanism for moving the drawing stylus in your hand along the time axis of the graph paper where you want to draw the complete music waveform. You could for example rely on a strip chart recorder, which could dispense the graph paper in strip form at a fixed time rate (you've probably seen strip chart recorders in the form of earthquake recorders, where the side to side needle motion indicates earthquake amplitude, on a steadily unrolling strip of graph paper; if you're unacquainted with this, imagine a roll of toilet paper unrolling at a steady rate). The strip chart recorder makes the graph paper move along under your hand at a constant speed, thus creating a steady time axis for the waveform you wish to draw. And the strip chart literally creates this time axis. Your hand is limited to reproducing (accurately we hope) only the amplitude axis of the music waveform, since you are now limited to side to side motion.

That's exactly what a turntable does. It literally creates the time axis half of your music waveform, while the cartridge, which is restricted to side to side motion, reproduces (accurately we hope) the amplitude information that the grove contains.

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Peter I forgot drive method. I have a Walker Ultimate motor controller plugged into an Exact Power 15 putting out a constant 120V, this combination keeps the speed as constant as I'm able to check.

Downunder,

Yup, that will irk you. Alas, that's a fine example of a poorly designed drive system; there's a reason the SDS was developed and that goes back to the AC mains. Trying to accurately derive 33.3 RPM using a crude phase shifting capacitor and hoping that the frequency of the incoming AC is stable enough to do the job is bad engineering. While frequency accuracy (and adjustablity) is one issue, it doesn't begin to address waveform shape, harmonic distortion, phase amplitude and shift, and all the other interesting things that go into generating a waveform suitable for driving a synchronous AC motor.

DC motors have their own set of problems...

I used to own a VPI TNT-V hot rod and a HRX.

EVERY time a pulled out the kab strobe the speed was different.

This had nothing to do with stylus drag.

If your platter is heavy, playing a record will not affect the speed.

That was the first quote from Don.

Needle drag does not slow down "Properly Designed" turntables!

That was the second quote from Don.
I guess I can agree with the second. it seems like a logical imperative :-)

Don,

You are simply wrong. Stylus drag will slow down any turntable, regardless of platter weight; it merely changes the period over which it occurs due to inertia. And yes, the 60Hz mains supply does fluctuate enough to be completely problematic.
Then again, if you can't hear it, more power to you.

Don_c55, try comparing a carefully tensioned cotton poly thread to the stock elastic band on your TNT. This will demonstrate the clearly audible difference between absolute and transient speed stability.

Halcro

Sutherland designs "CRAP" cold sounding phono stages!

They sound similar to HALCO amps!

The turntable in the video has a wimpy low torque motor drive system!!

Needle drag does not slow down "Properly Designed" turntables!

Halcro

Sutherland designs "CRAP" cold sounding phono stages!

They sound similar to HALCO amps!

The turntable in the video has a wimpy low torque motor drive system!!

Needle drag does not slow down well designed turntables!

If your platter is heavy, playing a record will not affect the speed

Written by a man who has no verifiable proof.
TIMELINE

The turntable speed should be at least as accurate as the tape recorders used to record, master, and playback the tape.

Constant speed is "much more" important than absolute speed.

Just buy a strobe disc and illuminate it with a light bulb.

The 60 Hz AC frequency does not fluctuate enough to worry over.

Adjust the speed of your turntable, or AC input (if you have a variable frequency supply like VPI SDS) for the lines or dots to appear stationary or slightly vary around a fixed position.

This is simple and more than sufficient. Tape decks are not all that accurate, and do go out of spec.

On my VPI TNT the SDS AC line frequency is set within .01 Hz.

If your platter is heavy, playing a record will not affect the speed.

Quite right Lew.
It really doesn't matter if your TT is revolving at 32.4rpm or 33.3rpm (other than pitch)......as long as it it is unwavering!
And that article you read was the one I posted by Peter Moncreif of the IAR. It was like a thunderbolt for me. The man is a real thinker :^)......in a field where there are some stinkers :^(

What Viridian said and Halcro hinted at. More important is stable speed regardless of groove modulation, as opposed to bang on 33.33 rpm. If a table can stay at 32 rpm whilst tracking any and all passages, then it could probably be adjusted to run stably at 33 rpm, so absolute speed is less of an issue, IMO. I read a very insightful piece somewhere on the internet last week which pointed out that the turntable provides fully "half" the music, as its speed past the stylus provides the horizontal axis of the complex sine waves that represent music, if it were graphically displayed for example with an oscilloscope. The cartridge can only give us the other half, the vertical or amplitude direction. All musical timing must come from the tt. Pretty sobering, eh? Well, I knew that, but I had never thought of it that way.

I have the Kab strobe disc and laser pointer which I have used reliably for the last two years and I have now just obtained the Sutherland Timeline laser weight.
The Timeline demonstrates that the Kab strode is merely an 'approximation' of correct speed.....or at least is not capable of detecting instantaneous 'stylus drag' which is clearly visible with the Timeline.
I can assure anyone......that once you have heard a record played without stylus drag.......speed constancy will become an important factor in your vinyl experience :^)

I like and use a digital tachometer for checking speed accuracy. I've tried strobe discs but like the tach more.

I suppose using a strobe disk and the Timeline laser then comparing the results. I don't lose much sleep over it...I use a strobe disk and that is good enough.