RPM: Check turntable speed with your iPhone?

ack

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Here's an interesting app https://itunes.apple.com/us/app/rpm-turntable-speed-accuracy/id1030889902?mt=8

You set it on top of the platter, and it uses the phone's gyroscope to calculate speed. I had high hopes for it, but it told me my table was too fast, and then I realized that even on steady surfaces the gyro shows a 0.25 +-0.01 rpm rotation. I don't think I can compensate the reading by subtracting 0.25 from it, because I am not convinced the gyro's error is constant. See what you get...

Sample screen:

 

ack

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It depends on the size of the iPhone; my 5 does not disturb the cartridge in the outer grooves.
 

ack

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In science, if your measurement approach interferes with the object under evaluation then your measurement is flawed, plain and simple. The iPhone is not any different. I was just curious and mostly interested in the speed variation, and it shows the same +-0.01 variation as still. So I take it for what it's worth - just another data point.
 
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amirm

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I wouldn't hold the still measurement against it. We need a calibrated system to compare it to. Doesn't anyone have a turntable with its own internal measurement display?
 

beaur

Fleetwood Sound
Oct 12, 2011
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The Feickert Platterspeed app and tone record have worked well for me. I tested it with a handheld rev meter and it seemed spot on. Plays a tone you pick up on your phone with the app.
 

Mosin

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Mar 11, 2012
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I thought the original RCA Victor LP rotation speed was 33 1/3 RPM, so 33.29 rpm seems pretty close???

That's close enough, but Ack nailed it.

Any tool is useful only as a guide for coarse adjustment, if it cannot show the consistency of a given rotation. Records were made at various speeds, but close to 33-1/3, so that is pretty much a target point. The main thing is that your turntable doesn't waver in its spin, and it is absolutely constant no matter what width of groove is thrown at it. The devil is in the details, as they say.
 

awsmone

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Apr 6, 2014
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i use free guitar tuner app and any test record this tells me the exact frequency which i check against the test track frequency the ultimate accuracy.... correct pitch :)
 

sombunya

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Oct 18, 2012
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I have that app and I've used it. It's free and it seems to work. Again, it's free. What do you want?

I've compared it to built in strobes and it's on. I know, arguments can be made against line voltage frequency and that means a strobe must be built.

My Rega RP3 runs a bit fast, almost 34 rpms. My Music Hall MMF 9.1 is spot on.

I'd think with all the crazy expensive and very exotic TT's around here there wouldn't be much need for it.
 

microstrip

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I have that app and I've used it. It's free and it seems to work. Again, it's free. What do you want?

I've compared it to built in strobes and it's on. I know, arguments can be made against line voltage frequency and that means a strobe must be built.

My Rega RP3 runs a bit fast, almost 34 rpms. My Music Hall MMF 9.1 is spot on.

I'd think with all the crazy expensive and very exotic TT's around here there wouldn't be much need for it.

European users sleep calm - they do not need fancy strobes to adjust their turntables. I use a quartz strobe since long and have found that it agrees with my 50Hz 230V LED lamp that sits close to the turntable. Just found why. In Europe we have a site that constantly monitors AC frequency with five digits and I saw that mains frequency is usually very accurate - most of the time better than 0.05% - equal or better than any professional reel tape machine.

If you are a very rigorous person you can see the exact mains frequency online and apply a correction to the strobe reading. See http://www.mainsfrequency.com/
 

ack

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ack

VIP/Donor & WBF Founding Member
May 6, 2010
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microstrip

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