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Stroboscopic disk sets wrong speed for turntable?

Hi all! I am new here.

I have just set up my Clearaudio concept turntable. Unfortunately, the speed of the turntable was wrong so I had to reset it. In order to do this I have used two methods: an iPhone app called RPM; the stroboscopic disk + the iPhone app StrobeLight.
The problem is that when everything is correct at 33 1/3 (both verified with the RPM app and the stroboscopic disk), the songs are playing one semitone lower than what they should. In order to make them play at the correct note, I have to set the speed at around 34 RMP as shown by the RPM app. Also the stroboscopic disk shows that now I am going faster than the 33 1/3, being consistent with the RMP app. How is this possible? Am I doing something wrong or even the stroboscopic disk is not accurate enough? Could it be the StrobeLight app not being an accurate enough light source for the stroboscopic disk? It is just peculiar that both the RMP app and the stroboscopic disk are consistent in saying that I am going too fast. 

Any help is much appreciated. Thanks!
agforte

Showing 3 responses by agforte

agforte OP
3 posts
 
I just tested again with the stroboscopic disk (bought from Pro-ject) and just an incandescent lightbulb, so no iPhone apps! I still have the same issue, at 33 1/3 the songs are played not in the right key. I am really puzzled!
agforte OP
3 posts
 
Hi all,

thank you for your answers. I am using a strobe disc that has both 50Hz and 60Hz markings. Since I am in the US I am using the 60Hz settings on the strobe light and on the disc.

I have also tested with a different iPhone app called Strobe Tachometer which seems more accurate than the other one I have used. However, it still tells me that the speed is a little too fast.
I do not have a set up record...I am assuming you mean a test record with a test sound. Correct?
agforte OP
3 posts
 
@bsmg I do not think this is a motor issue. The motor is working properly, it is just that if I want songs to be played in the right "note" or key, then the speed must read at around 34 RPM instead of 33 1/3.

I have tested with multiple LPs and with different songs of different bands. For example, at 33 1/3 Ticket To Ride by the Beatles plays in A flat instead of A. If I set the speed at around 34 then it correctly plays in A.
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