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 lewm

I keep forgetting to add one point I wanted to make with respect to the OP. Not only do I agree that the cell phone programs are notoriously inaccurate, but also so can a strobe be in accurate.  In many cases the 60 cycle frequency of the AC line is not stable. That can disrupt the frequency of any lamp that you plug into the wall. This is why I would recommend the KAB strobe. Which uses a battery operated strobe that is finely calibrated at 60 cycles. Plus the KAB device includes a disc that is wider in diameter than nearly any other I have seen.That also adds to its accuracy. And finally, it is not unusual to find that belt drive turntables without motor controllers can be slightly inaccurate as to speed. 
I thought it would be interesting if by some chance he had something substantive to say about phoenix engineering. I do agree with you about the general tenor of his posts.In this case, I am still waiting. And I think we will all wait forever for a specific comment.
Clearthink, can you take a step back from the ledge and say why you so detest Phoenix? It’s a serious question, because the products are highly regarded by the vast majority. Thanks.