Turntable Speed variances and acceptable levels?

Johnny Vinyl

Member Sponsor & WBF Founding Member
May 16, 2010
8,550
0
36
Calgary, AB
#1
Hi,

I have a Nottingham Analogue TT that has a low-torque motor, which is always on. There is no on/off switch and only requires a fairly gentle push of the platter to bring it up to its proper rotation. I have always found, and still do, that it's speed accuracy was very good and consistent. Of course this is only my assessment from listening to it, as I have no tools or other items to check for true accuracy. In listening, for instance, to APP-I Robot on vinyl and FLAC I can detect no difference. I have done this exercise several times in the last number of years.

Today I found an app on the Android Play Store called "RPM Calculator" and I downloaded it. It's very simple to use. Start the app and place it on your TT. Start your TT or in my case push the platter clockwise to bring it up to speed, which literally takes only a few seconds. The app then starts displaying the RPM it senses and hopefully it registers 33.3/45RPM with no variances as the platter makes each turn. My results are as follows:

33.3RPM: It consistantly indicated 34.4RPM with no variances. It was constant at 34.4RPM.
45RPM: The speed had variances and registered 46.2 and 46.1 per rotation. At about every third rotation it would briefly register 46.0 RPM.
* Each format was tested 3 times and for one minute and the results were identical.

The variances in the 45 RPM test have me somewhat confused. It measured speed changes within a rotation and then a different one for a split second on every full third rotation.

I have no idea how truly accurate this type of phone app is, so I'm not overly concerned, but I would love to hear some input from you guys.

More importantly however, and take away the app, is there an acceptable variance allowance for speed or MUST they always run at their designated speed? Is this even possible?
 

JackD201

[WBF Founding Member]
Apr 21, 2010
10,989
7
38
Manila, Philippines
#2
Hi Johnny,

I DJ so it goes without saying that I play lots of songs at the wrong speed! LOL! That said, on an intellectual level it can very well be bothersome to know that your pitch is up. You know, it's not what the artists intended. Personally, I'm not exactly sold on those apps. I'll take a strobe and a test disc any day.
 

Johnny Vinyl

Member Sponsor & WBF Founding Member
May 16, 2010
8,550
0
36
Calgary, AB
#3
Hi Johnny,

I DJ so it goes without saying that I play lots of songs at the wrong speed! LOL! That said, on an intellectual level it can very well be bothersome to know that your pitch is up. You know, it's not what the artists intended. Personally, I'm not exactly sold on those apps. I'll take a strobe and a test disc any day.
In comparing the LP and the FLAC files I can't hear a difference, so I'm thinking my real world experience is probably closer to accurate speed than not. It was an interesting exercise though. However, lets suppose the app gave me an accurate reading after doing a proper test with the strobe or test record to confirm. Are my results still acceptable?
 
May 27, 2013
402
0
16
Chicago suburbs
#4
I'm also a Nottingham Analogue owner, mine being the Dais which comes with their Wave Mechanic power supply. Tables like the Nottingham and many others use a simple AC motor to drive the platter, which sets the speed based upon the power line frequency of either 50 or 60 Hz depending upon your location. The problem with this type of setup is that the line frequency varies over time, although it is supposed to always average to the correct 50 or 60 Hz value. As such the rotational speed of the platter will also vary over time with the varying power line frequency. This is one reason for the existence of external AC turntable power supplies, which generate a clean and frequency stable sine wave to drive the platter at the correct speed. Nottingham's own design works well, and many other companies also offer similar dedicated power supplies. You just need to ensure that you get one designed for use with an AC motor drive system. Some will also offer electronic selection of 33 or 45 RPM without changing the belt's pulley although the Nottingham Wave Mechanic does not. It does have a fine speed control that you can use with the supplied strobe disc and battery operated LED light to accurately set the speed.
 

Johnny Vinyl

Member Sponsor & WBF Founding Member
May 16, 2010
8,550
0
36
Calgary, AB
#5
I'm also a Nottingham Analogue owner, mine being the Dais which comes with their Wave Mechanic power supply. Tables like the Nottingham and many others use a simple AC motor to drive the platter, which sets the speed based upon the power line frequency of either 50 or 60 Hz depending upon your location. The problem with this type of setup is that the line frequency varies over time, although it is supposed to always average to the correct 50 or 60 Hz value. As such the rotational speed of the platter will also vary over time with the varying power line frequency. This is one reason for the existence of external AC turntable power supplies, which generate a clean and frequency stable sine wave to drive the platter at the correct speed. Nottingham's own design works well, and many other companies also offer similar dedicated power supplies. You just need to ensure that you get one designed for use with an AC motor drive system. Some will also offer electronic selection of 33 or 45 RPM without changing the belt's pulley although the Nottingham Wave Mechanic does not. It does have a fine speed control that you can use with the supplied strobe disc and battery operated LED light to accurately set the speed.
I looked at getting the Wave Mechanic, but they want like $1,000 for it here in Canada. I don't have that kind of money, plus I'm not hearing anything untoward. Frankly I think my table plays just fine, but the app results just got me to thinking.
 

rbbert

Active Member
Dec 12, 2010
3,423
0
36
Reno, NV
#6
If your table is actually running at 34.4 RPM (over 3% fast), it will definitely be noticeable. even 33.4 RPM (~ 0.3%) probably be noticeable for many people in a direct comparison. That (jnd) for complex tones under 500 Hz (most human speech) is about 0.2-0.3%.

From wiki: The just-noticeable difference (jnd) (the threshold at which a change is perceived) depends on the tone's frequency content. Below 500 Hz, the jnd is about 3 Hz for sine waves, and 1 Hz for complex tones; above 1000 Hz, the jnd for sine waves is about 0.6% (about 10 cents).[19] The jnd is typically tested by playing two tones in quick succession with the listener asked if there was a difference in their pitches.[12] The jnd becomes smaller if the two tones are played simultaneously as the listener is then able to discern beat frequencies. The total number of perceptible pitch steps in the range of human hearing is about 1,400; the total number of notes in the equal-tempered scale, from 16 to 16,000 Hz, is 120.[12]
 

morricab

Active Member
Apr 25, 2014
2,287
3
38
Switzerland
#7
Hi,

I have a Nottingham Analogue TT that has a low-torque motor, which is always on. There is no on/off switch and only requires a fairly gentle push of the platter to bring it up to its proper rotation. I have always found, and still do, that it's speed accuracy was very good and consistent. Of course this is only my assessment from listening to it, as I have no tools or other items to check for true accuracy. In listening, for instance, to APP-I Robot on vinyl and FLAC I can detect no difference. I have done this exercise several times in the last number of years.

Today I found an app on the Android Play Store called "RPM Calculator" and I downloaded it. It's very simple to use. Start the app and place it on your TT. Start your TT or in my case push the platter clockwise to bring it up to speed, which literally takes only a few seconds. The app then starts displaying the RPM it senses and hopefully it registers 33.3/45RPM with no variances as the platter makes each turn. My results are as follows:

33.3RPM: It consistantly indicated 34.4RPM with no variances. It was constant at 34.4RPM.
45RPM: The speed had variances and registered 46.2 and 46.1 per rotation. At about every third rotation it would briefly register 46.0 RPM.
* Each format was tested 3 times and for one minute and the results were identical.

The variances in the 45 RPM test have me somewhat confused. It measured speed changes within a rotation and then a different one for a split second on every full third rotation.

I have no idea how truly accurate this type of phone app is, so I'm not overly concerned, but I would love to hear some input from you guys.

More importantly however, and take away the app, is there an acceptable variance allowance for speed or MUST they always run at their designated speed? Is this even possible?
Is that while playing the record? If you want a really accurate speed strobe then get the Allnic Speednic...not so cheap but it is really good. You can measure while playing a record and on some TTs you will see speed variation while the needle drag is varying through the record.
 
Jun 17, 2010
256
0
16
SE Pa
#8
Hi Johnny,
I'll take a strobe and a test disc any day.
yep, I agree, I utilize a test disc and a portable fluorescent drop light, works perfect ! But then I have an SDS on my VPI Aries III so it's used to calibrate 45 and 33 1/3 settings.
 
May 25, 2010
742
7
18
SF Bay Area
#9
Johnny, I think you are talking about two different issues.
1. The absolute speed of your TT
2. Variability in the speed.

The first, and typically I have read mostly about TT's that run fast - means that you will be hearing music that is being played at a slightly higher pitch than the original and slightly faster than the original. Famously, Kind of Blue had some cuts that made it to the record at a slightly higher speed than originally recorded (problem with playback equipment IIRC). This was later corrected, but all the original records have that problem. There are some other examples, too. One of the most egregious was when Murray Hill issued the complete Ring cycle of Furtwangler on 11 records, where normally they would take at least 16 to 19 records. What they did was speed up the tapes and everything would fit on the records! The human voice is probably most sensitive to playing the wrong pitch - at the extreme the voice sounds like the chipmunks (David Seville did that trick to create the chipmunks sound). The advantage to playing the music at a faster speed is that you can play more records in a given period of time, sort of like a Reader's Digest version of the album. :)

The second will create wow. This can be very annoying, particularly when playing a piano record with long sustained notes. People vary a lot in sensitivity to wow. I have a friend who is very sensitive. Many years ago he was at the house and told me that he could hear the wow in the system. I couldn't hear a problem, but when I measured it, there was wow. It is harder to hear with a human voice, since there is often some vibrato which hides the wow.

The problem I have had with a strobe disc is that it generally is much lighter than an LP, especially a 200g LP. so unless you put the disc on the record, which I think most people don't do, the speed you are measuring with the strobe disc will be slightly faster than with the LP. I use an industrial instrument, a Monarch PT99 which comes with a short roll of reflective tape. You tape a very short piece onto the side of your TT platter and use the instrument to measure the speed. It can read up to the thousandth place, and is accurate to a few thousandths. So I can set my TT (VPI with an SDS) to 33.333 and it will vary in the thousandth place. So I can get the speed to 33.333 +- .005 or so. It will vary with temperature (the belt expands and contracts) so I check it through the day every few records and make small adjustments. This was true when I was doing my ripping project, when I sometimes ripped a dozen or more LP's in one day.

Larry
 
May 30, 2010
13,925
14
38
Portugal
#10
I'm also a Nottingham Analogue owner, mine being the Dais which comes with their Wave Mechanic power supply. Tables like the Nottingham and many others use a simple AC motor to drive the platter, which sets the speed based upon the power line frequency of either 50 or 60 Hz depending upon your location. The problem with this type of setup is that the line frequency varies over time, although it is supposed to always average to the correct 50 or 60 Hz value. As such the rotational speed of the platter will also vary over time with the varying power line frequency. This is one reason for the existence of external AC turntable power supplies, which generate a clean and frequency stable sine wave to drive the platter at the correct speed. Nottingham's own design works well, and many other companies also offer similar dedicated power supplies. You just need to ensure that you get one designed for use with an AC motor drive system. Some will also offer electronic selection of 33 or 45 RPM without changing the belt's pulley although the Nottingham Wave Mechanic does not. It does have a fine speed control that you can use with the supplied strobe disc and battery operated LED light to accurately set the speed.
This type of accessory has fancy names, but it is usually simply a two phase power supply - something that has been known since long. The most interesting feature of some models is that they have variable amplitude - higher at startup for a few seconds, from then on a reduced value to operate the motor in the best zone. Ideally it should be matched or tuned to the motor. Then you can play with small adjustments in phase and amplitude to overcome any motor non linearity.

Any one can build such device with a soundcard, a two channel power amplifiers and two small power transformers - I have done it to power a 60 Hz synchronous motor in Europe!
 

morricab

Active Member
Apr 25, 2014
2,287
3
38
Switzerland
#11
Johnny, I think you are talking about two different issues.
1. The absolute speed of your TT
2. Variability in the speed.

The first, and typically I have read mostly about TT's that run fast - means that you will be hearing music that is being played at a slightly higher pitch than the original and slightly faster than the original. Famously, Kind of Blue had some cuts that made it to the record at a slightly higher speed than originally recorded (problem with playback equipment IIRC). This was later corrected, but all the original records have that problem. There are some other examples, too. One of the most egregious was when Murray Hill issued the complete Ring cycle of Furtwangler on 11 records, where normally they would take at least 16 to 19 records. What they did was speed up the tapes and everything would fit on the records! The human voice is probably most sensitive to playing the wrong pitch - at the extreme the voice sounds like the chipmunks (David Seville did that trick to create the chipmunks sound). The advantage to playing the music at a faster speed is that you can play more records in a given period of time, sort of like a Reader's Digest version of the album. :)

The second will create wow. This can be very annoying, particularly when playing a piano record with long sustained notes. People vary a lot in sensitivity to wow. I have a friend who is very sensitive. Many years ago he was at the house and told me that he could hear the wow in the system. I couldn't hear a problem, but when I measured it, there was wow. It is harder to hear with a human voice, since there is often some vibrato which hides the wow.

The problem I have had with a strobe disc is that it generally is much lighter than an LP, especially a 200g LP. so unless you put the disc on the record, which I think most people don't do, the speed you are measuring with the strobe disc will be slightly faster than with the LP. I use an industrial instrument, a Monarch PT99 which comes with a short roll of reflective tape. You tape a very short piece onto the side of your TT platter and use the instrument to measure the speed. It can read up to the thousandth place, and is accurate to a few thousandths. So I can set my TT (VPI with an SDS) to 33.333 and it will vary in the thousandth place. So I can get the speed to 33.333 +- .005 or so. It will vary with temperature (the belt expands and contracts) so I check it through the day every few records and make small adjustments. This was true when I was doing my ripping project, when I sometimes ripped a dozen or more LP's in one day.

Larry
This is why a speed device where you can measure while a record is actually playing is useful. I am senstitive to wow, and a friend of mine is as well and he said he had never heard piano sustain so stable as heard at my place with a really good DD turntable. The Allnic Speednic is such a device with high accuracy as well.
 

Lagonda

VIP/Donor
Feb 4, 2014
227
0
16
Denmark
#12
There is a nice free app for iPhone's that will measure the speed during real playback, it's from the German TT maker Dr.Feickert, and is called "PlatterSpeed". You put on a test record ( I use one from Analogue Productions )and play a 3150 Hz test tone.
The app samples the tone trough the phones microphone and gives you a very accurate readout !

Have fun with it !
 

morricab

Active Member
Apr 25, 2014
2,287
3
38
Switzerland
#13
In comparing the LP and the FLAC files I can't hear a difference, so I'm thinking my real world experience is probably closer to accurate speed than not. It was an interesting exercise though. However, lets suppose the app gave me an accurate reading after doing a proper test with the strobe or test record to confirm. Are my results still acceptable?
I think you need something more moment by moment to see if the speed fluctuates a lot...particularly during actual record playing conditions.
 
Jul 25, 2012
2,553
0
36
NY
#14
Hi,

. . . . Today I found an app on the Android Play Store called "RPM Calculator" and I downloaded it. It's very simple to use. Start the app and place it on your TT. Start your TT or in my case push the platter clockwise to bring it up to speed, which literally takes only a few seconds. The app then starts displaying the RPM it senses and hopefully it registers 33.3/45RPM with no variances as the platter makes each turn. My results are as follows:

33.3RPM: It consistantly indicated 34.4RPM with no variances. It was constant at 34.4RPM.
45RPM: The speed had variances and registered 46.2 and 46.1 per rotation. At about every third rotation it would briefly register 46.0 RPM.
* Each format was tested 3 times and for one minute and the results were identical.

. . . . More importantly however, and take away the app, is there an acceptable variance allowance for speed or MUST they always run at their designated speed? Is this even possible?
A turntable that was off even slightly always bothered the hell out of my brother and daughter who both have perfect pitch. One that is off by 3% would drive them out of their minds.

A turntable playing middle C at 269 Hz would be torture.