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Thread: Turntable Speed variances and acceptable levels?

  1. #11
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    Quote Originally Posted by astrotoy View Post
    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.

  2. #12
    VIP/Donor [VIP/Donor] Lagonda's Avatar
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    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 !
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  3. #13
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    Quote Originally Posted by Johnny Vinyl View Post
    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.
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  4. #14
    Member Sponsor [VIP/Donor] GaryProtein's Avatar
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    Quote Originally Posted by Johnny Vinyl View Post
    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.
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