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Turntable speed measurement

R

Rk19

pfm Member
Looking for alternatives to strobe and found an app - Turntabulator for iPhone. Have tried it and seems as accurate as strobe but much easier. No set up involved. But- I do not understand it's mechanism not using the gyros. Quote "Through the power of Musical Analysis with Gyroscopically Indifferent Calculations (MAGIC), no gyroscope is required, so Turntabulator works just fine on the iPhone 3GS. In fact, the results are more accurate than the iPhone or iPod Touch gyroscope would provide". Can anyone explain this to me?
 
Just analysing the sound of the cartridge in the run out groove would work. The periodic click at 33.3 rpm is easily detectable and averaged over enough time will give as accurate a measurement as you want
 
What's the problem with using a strobe? A sufficiently proven method that t/t manufacturers have even incorporated it into their designs.
 
If a turntable cannot manage an average of 33.3 rpm it has big problems.

What is needed is to measure the speed within 1 revolution, showing potential issues of motor cogging, stylus drag and power supply variations.
 
Many run fast by design from new for a more exciting sound.
Aged units can be all over the place due to power supplies and bearings
 
There's no point in measuring mine, because even if it IS slightly off, I have no means of adjusting it.

How many TTs do? Not Rega, Pro-ject, Linn ...
 
I use a similar app called RPM that also locks the display to the same viewpoint as the phone sits/spins on the platter.

My Origin Live has a seperate motor unit so if you ever knock or move it the belt tension and therefore speed changes so it does come in handy.
 
formbypc said:
There's no point in measuring mine, because even if it IS slightly off, I have no means of adjusting it.

How many TTs do? Not Rega, Pro-ject, Linn ...
Click to expand...

I seem to recall that the LP12's speed can be adjusted by changing the tilt of the motor. No idea what the adjustable range is likely to be though.

Mick
 
Wolfmancatsup said:
I seem to recall that the LP12's speed can be adjusted by changing the tilt of the motor. No idea what the adjustable range is likely to be though.

Mick
Click to expand...

I use a very primitive measure. A blob of blue tax on the platter, time 100 revolutions and divide by 3. It's suprisingly accurate, at least I think it is.
 
As long as it is very close to 33 1/3, it isn't an issue. What is far more important is that it is constant.
 
Wolfmancatsup said:
I seem to recall that the LP12's speed can be adjusted by changing the tilt of the motor. No idea what the adjustable range is likely to be though.

Mick
Click to expand...

This is true; the LP12's speed can be adjusted using the "tilt" screws on either side of the motor. These should be used carefully, as it is possible to bend the mounting "wings" of the motor or otherwise damage the motor if you manhandle these screws. I'm not sure what the range of adjustment is, but on mine it was pretty easy to get the speed virtually spot on using both turntabulator and a more traditional strobe.
 
I've used an app called platter speed which uses the output of a fixed frequency record tone to determine real time speed. However, you will need to carefully re position the centre hole in order to achieve exact results. But the advantage is it will give you an insight in to the characteristics of the drive system, not just whether 33.3 revolutions are achieved in one minute.
 
Just measured my rp6 using the rpm app and with no stylus drag it shows 33.65rpm or a whisker under 1% fast...

Thought use revisit this after watching the final of the rega factory visits and the discussion around belts...I swapped the twin silicon belts I had been using for a pair of white (well one is white the other is brown) rega belts and re measured the speed... my previous 33.6 rpm or 1% fast fell to 33.45... so rega do know what they are talking about!
 
hifi-dog said:
Just measured my rp6 using the rpm app and with no stylus drag it shows 33.65rpm or a whisker under 1% fast...
Click to expand...

If it's an AC motor then it will be the same speed when playing a record.

You could possibly solve this with a smaller diameter (as in cross section) belt, this would fractionally change the gearing.

I would be tempted to do the counting trick as outlined above (100 revolutions in 3 minutes) I know it's a painful 3 minutes but it is accurate. The more I think about it, 33.6 is way off what you should expect.
 
TPA said:
If it's an AC motor then it will be the same speed when playing a record.

You could possibly solve this with a smaller diameter (as in cross section) belt, this would fractionally change the gearing.

I would be tempted to do the counting trick as outlined above (100 revolutions in 3 minutes) I know it's a painful 3 minutes but it is accurate. The more I think about it, 33.6 is way off what you should expect.
Click to expand...

It isn't way off for a Rega, they run around 1% fast (surprised this is still the case with the newer ones), which I think might be a deliberate decision on Rega's side.
 
Simple digital tach works for me

24gk46g.jpg
 
Rega rp6 is 24h dc motor with quartz synchro tt psu so should be bang on I hoped. but hey life's to short and it sounds fine esp as classical piano etc is not my bag
 
hifi-dog said:
Rega rp6 is 24h dc motor with quartz synchro tt psu so should be bang on I hoped. but hey life's to short and it sounds fine esp as classical piano etc is not my bag
Click to expand...

End of the day a lot of people love the Rega balance. There's more to life than being bang on 33.3RPM indeed.
 
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