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

fsonicsmith
"
There is nothing better than the now defunct Phoenix Engineering Road Runner"

The "Roadrunner" was as unreliable, poorly engineered, and flawed concept, design, and execution promoted by an unhappy, angry, vicious marketer who thought he knew everything there was to know about everything there is to know it is not a wonder, surprise, or mystery as to why his "business" folded abruptly, quickly, and without notice and that none of the other manufacturers he sought to continue its manufacture, production, and support were willing to affix their name to the product.
@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.
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!
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.
Strange......maybe it's just a rounding error on your measuring device since the other two speeds you have are 45 and 78....whole integers. Anyway, those were the only things I would have done myself (toggle the speed selector and set back to 33.3 and check the belt) After that, I would probably cuss and fuss.