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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
Post removed 
clearthink
1,421 posts
 
Most iPhone apps are junk if you are dedicated, serious, and determined to obtain proper performance from your Music Reproduction System I suggest, recommend, and encourage you to purchase, borrow, or acquire proper, dedicated, precise tools to achieve correct setup, alignment, and calibration.
glennewdick's avatar
glennewdick
1,689 posts
 

If your using a north American 60hz strobe disc just use an incandescent light bulb for your light source. if you have a 50hz disc then that could be your issue.

 That's all the lights are for built in speed control on record players that have that feature.

much more accurate then any phone app as well.

 Also are you using a set up record?

agforte OP
10 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?
fsonicsmith's avatar
fsonicsmith
959 posts
 
There is nothing  better than the now defunct Phoenix Engineering Road Runner. It was hoped that Sota would re-introduce the product but it seems not at present. The design is not that complicated. A magnet and a sensor and a simple IC chip in a box to a read-out display. One would think there would be a ton of Chinese made cheap knock-offs but nope. 
Strobes are second-best but they almost always waver back and forth. Most platter engravings are slightly off. And then even if you set proper speed at one point in time, there is speed drift caused by motor warming, variations in voltage, and even stylus drag. The combined PE Road Runner and Eagle PSU was unbeatable, both for ultimate speed stability and value. But overall, the importance of exactly precise rotational speed is overstated imho. How else would Rega get away with fast tables for all these years? Mikey is fond of saying "precise speed is job 1 for any turntable". Rubbish. Lack of noise is number one-motor induced, bearing induced, stylus-record induced, et al. And even then, an argument can be made that the white noise associated with vinyl playback is largely why it sounds so good. It masks a lot of evils. I have a longstanding feud with Mikey (not that he gives it much notice other than an occasional solar flare) over this exact issue. Mikey expects ultimate vinyl playback to compete with digital for low noise floor and detail retrieval. I find that to be a waste of time, effort, and expense not to mention an impossible goal and a misdirected one. 
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