What's the speed of your turntable?

Discussion in 'Audio Hardware' started by TVC15, Jul 12, 2015.

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  1. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    Some of the comments on the amount of error early in this thread were interesting, when you considering rounding has to occur somewhere. In theory, the correct speed is 33 1/3, rather than 33.33. A display of 33.33 had to round off further digits past the two it displays, so assuming the rounding is to the nearest it could have been anywhere from 33.325 to 33.335. A display of 33.34 could have been anywhere from 33.335 to 33.345. A display of 33.34 isn’t necessarily off by .01. It could be off by less than .002. A display of 33.33 could be off of 33 1/3 by as much or more than 33.34.
     
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  2. punkmusick

    punkmusick Amateur drummer

    Location:
    Brazil
    It is impossible to measure exactly 33 1/3, it's a repeating decimal. Somewhere we must make an approximation.
     
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  3. cadeallaw

    cadeallaw Forum Resident

    Location:
    Dayton, OH
    My Clearaudio was a good rpm off... adjusted the speed with the little screw thingys and now it is perfect
     
  4. eflatminor

    eflatminor Forum Resident

    Location:
    Nevada
    You can play with the belt as others have suggested (talc, new positions, new belt, etc.) or I would think you could but a power conditioner/speed controller from Nottingham...the same one that comes with the DAIS and Anna Log. Not sure if they sell them separately, but they should!
     
  5. eflatminor

    eflatminor Forum Resident

    Location:
    Nevada
    I'm using the Sutherland Engineering Timeline. Overkill? Probably, but I like the notion of being able to measure the speed while the stylus is in the groove and with the weight of any record clamp you might use taken into consideration. [​IMG]
     
  6. chili555

    chili555 Forum Resident

    I agree with your post in its entirety. However, if anyone here thinks that they can accurately discern the difference between 33.333333333... rpm and 33.34 rpm, I will be shocked. Moreover, if any of our turntables can, with laboratory grade equipment, be shown to have less wow than +- 0.01 rpm, I will be even more shocked!

    What I got from this thread and what I think most of you get, is to check the speed by whatever means possible and correct it to get as close to 33.33 rpm as shaky hands and trimpots can get you.
     
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  7. Tony Plachy

    Tony Plachy Senior Member

    Location:
    Pleasantville, NY
    You are correct that 33 1/3 is 33.333333333333333333....... which means that it is an infinite series of 3's after the decimal point. You are also correct that if you have a digital readout you can never know for sure that your speed is exactly 33 1/3, however, if you readout has four or more decimal places and they are all 3's you can be sure that any deviation from 33 1/3 is not audible. You can measure 33 1/3 exactly using a very good strobe setup and letting the TT warm up for an hour or so, however, when using a strobe to check the speed you still have to worry about the impact of stylus friction if you want to go crazy on this matter. As I said in an earlier post my main concern is constant speed (i.e. very low wow and flutter) and a quiet table (very low rumble). Obviously while not being concerned about the speed being exactly 33 1/3 you want the speed to be reasonably close to it.
     
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  8. punkmusick

    punkmusick Amateur drummer

    Location:
    Brazil
    I agree. I believe that if you measure speed and it is somewhere between 33.2 and 33.4 amost constant, i.e., with very small variations (maybe from 33.25 to 33.3 each cycle) you would have what is reasonable to demand and nothing to worry about. Maybe even less precise that this would be acceptable.
     
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  9. SteelyNJ

    SteelyNJ Forum Resident

    Location:
    New Jersey, USA
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  10. SteelyNJ

    SteelyNJ Forum Resident

    Location:
    New Jersey, USA
    I removed my iPhone 7 from its case and ran the calibration mode on my Technics SL-1200MK2. It came up with a multiplier of 1.0004. Multiple speed tests with the applied calibration factor yielded a result of 33.37 RPM on the app. Is it correct? I have no idea.
     
  11. punkmusick

    punkmusick Amateur drummer

    Location:
    Brazil
    For some reason I tend to trust your SL1200's accuracy better than that of the iPhone. I would judge the iPhone's accuracy based on the Technics and not the other way around: if RPM says 33.37, so it is 0.03-0.04 innacurate comparing to the Technics.
     
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  12. TerryS

    TerryS Forum Resident

    Location:
    Peyton, Colorado
    I'm sure it has been mentioned before, but a good way to check the accuracy is to count the number of revolutions on your platter in 3 minutes (180 seconds). There should be exactly 100 revolutions. Since you should pretty easily be able to see an error of +/- 1/4 revolution, this means you can tell the accuracy to 0.25% or better. If you have the patience to count for a longer time, you can improve the accuracy of your measurement.
     
  13. SteelyNJ

    SteelyNJ Forum Resident

    Location:
    New Jersey, USA
    Actually, I think you're suspicions about the quartz-locked accuracy of the Technics TT vs. the iPhone are 100% correct. In addition to the SL-1200, I also have a Dual 510 table and it, too, consistently registered slightly faster than 33.33 on the RPM app tests (33.39 with the "calibration multiplier" applied and 33.37 without). Although it's belt driven and not quartz-locked, the Dual employs a sensitive lighted strobe speed indicator that holds virtually motionless over time, proving both stability and accuracy. I find it hard to believe that my Technics and my Dual turntables are BOTH running fast when their respective built-in strobe gauges indicate true 33.33 RPM speeds.
     
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  14. Henry Phillpotts

    Henry Phillpotts Well-Known Member

    Location:
    Oxford, UK
    My project debut carbon was wobbling between 32.9 and 33.4 but once I bought a linear PSU it locked in at 33.3. From that experience I can recommend looking at your power supply, i think spikes often cause the deviations and a regulated supply cost me less than £100 which was worth every penny.
     
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  15. Mr Bass

    Mr Bass Chevelle Ma Belle

    Location:
    Mid Atlantic
    Running at 33.33 but I have a digital speed controller and alternate between two belts to minimize stretching. Allowing one belt to rest for a month or two lets it shrink back to spec.
     
  16. SteelyNJ

    SteelyNJ Forum Resident

    Location:
    New Jersey, USA
    Anyone else try the RPM app with calibration on an iPhone?
     
  17. Recently upgraded from an RP6 to an RP 8. It was a four month old demo unit. It runs at 33.4.
     
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  18. Davey

    Davey NP: Portishead ~ Portishead (1997)

    Location:
    SF Bay Area, USA
    I have one of those inexpensive laser tachometers, $11.99 at amazon, you put a reflector dot or strip on something then press the button to read the RPM. So for a bit more accuracy and update speed on my turntable, I use 12 reflectors around the outside of the platter instead of just one. That means one placed every 30 degrees around the circumference, so 33 1/3 RPM will read 400 RPM on the tach display. Below is what it reads, pretty close, this is on my Clearaudio Avantgarde with AC synchronous motor plugged directly into wall socket...

    [​IMG]
     
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  19. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Cool. To increase the precision, point it at the 60hz/33rpm dots on your turntable ring (or print a strobe ring), and divide the tach reading by 216. The laser dot must be small enough to detect the black/white transitions.

    It still relies on the accuracy of the timebase or oscillator in the measurement device, so your $12 may not buy a lot of confidence in the reading.
     
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  20. punkmusick

    punkmusick Amateur drummer

    Location:
    Brazil
    I would trust your Clearaudio Avantgarde to evaluate this device and not the other way around. This test proves it is a great measurement device.
     
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  21. Manimal

    Manimal Forum Resident

    Location:
    Southern US
    High speed....low drag:)
     
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  22. Davey

    Davey NP: Portishead ~ Portishead (1997)

    Location:
    SF Bay Area, USA
    Sure, but it's a quartz crystal so likely pretty close, I doubt my placement of the reflector dots was done with enough precision to tax the accuracy of the tach. The spec says +/- .05% of reading + 1 least significant digit. Least significant digit is 0.1 RPM and .05% of 400 is 0.2 RPM. So worst case at 400 RPM would be 0.3 RPM, which translates to .025 RPM at 33 1/3 RPM, close enough for my needs :)
     
    Last edited: Aug 19, 2018
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  23. BayouTiger

    BayouTiger Forum Resident

    The Project Perspex comes out 33.36. Not too bad. The Oracle Delphi MKV says 33.22. The weight of the iPhone makes the Oracle's tripod suspension droop as it rotates I wonder how the slight vertical movement affects the phone's measurement?? Probably not enough to matter. Now I gotta pull the trusty 1200 out to see what an aged direct drive does by comparison.
     
  24. mitchius

    mitchius Forum Resident

    Location:
    Jamison Pa
    Did you test your Perspex for 45? I got 33.34 and 45.19. I don’t know if that 45 speed is significant enough to be an issue.
    Thanks, Mitch
     
  25. BayouTiger

    BayouTiger Forum Resident

    45.09 I figure close enough.

    The 1200MkII did 33.33 and 45.00 just as I figured it would! :)
     
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