What's the speed of your turntable?

VPI Scout with iRPM app with the belt at the top 1/3 of the motor spindle fluctuates between 33.3 and 33.4. The app doesn't give any more detail or go out anymore decimal places.

 

Not a phone app but here is a screenshot of my Fieckert Adjust Plus program. This shows speed and variation (the shaded area):

 

How does the Turntabulator measure the rpm's?

So you simply put the phone on the platter and give it a spin!

 

yup!

 

I have to say I am somewhat amazed at how much technology goes into doing things today that use to be done with very little technology. Since I do not have a smart phone I will continue to use my strobe disc and battery operated strobe light.

 

Would that be accurate to the 100th of an RPM? Would a strobe tell you the actual speed at which your table is running?

 

Is this on your VPI Aries with SDS?

 

The test record seems very good, not much difference if the 0.55Hz is filtered out. Don´t know what they mean by 2-Sigma in this case.

 

Strobes will not tell the actual speed in number form (obviously) but they are surprisingly accurate when used correctly.

 

OK, So lets sort this out. I have a KAB Speed Strobe. I consist of a battery powered quartz crystal controlled oscillator that runs the light and a lithographically printed pattern on a heavy black plastic disc. KAB claims that if you can achieve a stable pattern then you are good to 99.99% (0.0001 x 33.33 = .0033) or about 3.3/1000 of an rpm. So how do we put theory into practice. My TNT-HR comes with a VPI SSD speed controller that allows you to change the input frequency to the motor by 0.01 Hz. Now for me it is possible to determine within 0.01 Hz which frequency gives the most stable pattern when using the strobe and disc. 60.01/60.00 = 0.9998 0r 99.98% accurate. Thus the VPI SSD has about twice the amount of inaccuracy as the KAB Speed Strobe does which means it is about 7/1000 of an rpm. At this point I am going to pull a fast one on you guys and put on my Dr. Plachy (Ph.D. Physics, 1980) hat. I am telling you that since there is no reason to expect that the error in the strobe and disc is in anyway correlated to the error in SSD and TT motor, that the proper way to combine these two errors is to square each, add the squares and take the square root of the sum (got that ). That gives 7.6/1000 of an rpm error for the two combined errors. If you squint 7.6/1000 is about equal to 10/1000 or 1/100 of an rpm. Which means this may be ever so slightly better than the smart phone method.

 

I don't want to know as I have enough to obsess about already. Being an audiophile makes me crazy and this isn't helping. ;>0

 

Ray, Your TT is pretty darn good. The average rotation speed is only 0.01 RPM off of 33.33 RPM. I doubt if a person with perfect pitch would hear that. The Wow and Flutter, however, totally overwhelm the 0.01 RPM inaccuracy. The max deviation from 33.34 RPM is +/- 0.08 RPM (unfiltered data) and what the DIN 2 sigma stuff means is that 95% of the time the deviation from is only +/- 0.03 RPM. Keep the TT.

 

Yes

 

Scout 1.1 w/Eagle and Roadrunner, 33.331-7.

 

Awesome!!!

 

VPI Classic 2 w/ SDS:

• 33.33
• 45.0

This just confirms my Fieckert calibration works!

 

I'm not sure about this, but I believe the unfiltered is to be ignored???

Meanwhile, liking the results from the VPIs so far. My old Classic was also dead accurate.

Where are the Rega owners??

 

Aww, come on Jim! It's not being an Audiophile that makes you crazy! Crazy people become audiophiles!!

 

Stock RP6 33.4

Wondering if I could hear .07 of a difference. I have an SL1200 but so don't want to swap out again. Also wonder if the groove tracer subplatter will fix that. I never even give the speed a second thought till I come across speed posts. Ugh

 

How does the Roadrunner measure the actual platter speed?

I question the accuracy of any smartphone app because they are relying on the system clock, which is a fifty cent crystal that varies a lot with internal temperature. Generally computer system clocks are not accurate and accurate timekeeping is done by frequent updating. A test disc with an accurate musical note and a decent musical instrument tuner would be better. Even then, you should check it against a known accurate reference such as a frequency counter that has a OCXO or TCXO source or is hooked to a high accuracy timebase.

 

My turntable is fast (33.7) , just like my women.

 

My P25 runs 33.7-33.8 fast and snappy and that's with all the Groovetracer mods...

 

33.4 is OK. Within spec, I think.

It was my Rega RP8 that made me want to measure in the first place. Something (actually Yes' Heart of the Sunrise, which I know very well and can play along with on the bass) sounding a bit too 'snappy' (and maybe a little sharp) to me. So I measured and it was running at ~33.6!!

Turntabulator and Feickert w/ 3150z test disk report the same results on my end.....

WOW! That's into sonically obvious territory, no? You could try a Little Belter to slow it down.

Rega RP6 with Groovetracer?

 

I run tables with infinitely variable speed--a Strathclyde and a Fons. Never used the apps under discussion, but I have checked the Fons with an external digital tachometer, and it can be adjusted to a pretty consistent 33.3 RPM (generally measured while not under load). The Strathclyde has a built-in digital display, and it, too, can be set to 33.3, although it seems to "wobble" a bit when under load. Of course, I'm far more concerned with variation around 78 RPM, and both will do wide enough a range to cover the commonly found speeds of pre-electric recordings (i.e., from somewhere in the 60s to around 90).

Incidentally, I have also used the digital tachometer to set my Edison "Edisonic Schubert" diamond disc machine to as close to an even 80 and my Edison Triumph cylinder machine to as close to 160 as was doable with spring motors of between 90 and 110 years' service.

 

"90 miles an hour baby, is the speed I drive..."