3 New UBER Decks - Is this Turntable's SwanSong? 🦢

Halcro.

I think that the numbers and green graph are useful provided their limitations are taken into account.

Mean frequency....

This is a good number to have. We are looking for 3150Hz, so nice and close to this is desirable.

Raw frequency…

Max deviation. (relative ) This is the max percentage deviation, negative and positive, from the mean frequency. Ideally the two numbers should be the same

Max deviation (absolute) This is the max frequency deviation, negative and positive from the mean frequency. Ideally the two numbers should be the same.

What the deviation numbers do not show is the variation between the deviation of individual positive and negative swings. They all should be the same, (constant amplitude) and for this information we need to refer to the yellow graph.

Lowpass-filtered Frequency.....

This data taken from the green trace. The limitation here is that this trace is heavily filtered version of the yellow trace. And it is very inconsistent from test to test.

Look at the 1000R yellow trace and compare this with the TT-101 yellow trace. There is an enormous difference yet, post filtering they yield very similar green traces  

I have run sequential tests on my SP10 Mk 3 and got Low pass -0.01%/+0.01% followed by -0.02%/ +0.03%. I have outlined some of the reasons for this inconsistency. As I said earlier, below a certain percentage, these figures aren't robust.

Obviously we do not want to see any standout perturbations in the green trace and in this way it can be very useful.

My point is that this data is derived from the yellow trace which is taken from the cartridge output. After all, it is the cartridge’s output that we listen to. To really see how the TT is behaving in fine detail, we need to analyse the yellow trace from the perspective of what a perfectly speed stable TT would look like. A clean sine wave, symmetrically centred around 3150hz with a constant amplitude for each cycle. As we can see, advances in technology have clearly improved the situation.  

 The subsonic speed resonance in the TT-101 can be seen as periodic cycling every 5 revolutions. If you look at the first traces you posted (yellow) , you will see a positive peak just after 5 seconds. This peak appears again just after14 and 23 seconds. The smaller positive and negative excursions in between these peaks follow the same pattern with their 9 second spaced partners. There is a recurring pattern to the shape of this waveform with a period of 9 seconds.  

Cheers,

The GRAPH produced with the PlatterSpeed App is accurate and USEABLE when looking at the 'Green' Lowpass-Filtered Frequency.
If the hole was PERFECTLY centred.....this 'Green' line would be perfectly STRAIGHT......but only if the turntable was maintaining its speed PERFECTLY.
So the best performing turntables are those with the most constant and even wobbles approaching as closely as possible a STRAIGHT LINE.

A far more accurate and useful metric of the speed accuracy of a TT is to simply look at the raw yellow trace, ignoring the numbers. How close is it to the ideal symmetrical, clean, constant amplitude, sine wave?

A clean sine wave, symmetrically centred around 3150hz with a constant amplitude for each cycle. As we can see, advances in technology have clearly improved the situation.

@halcro

It’s all smoke and mirrors and fanciful postulation from the uneducated. It is not possible to measure wow & flutter using a test record.

If you use a rotary function generator to measure the turntable performance directly off the platter, the results will be more accurate than any test record.

For an explanation from someone who actually has a degree in physics and acoustical engineering - Bruce Thigpen of Eminent Technology.

Here is Bruces explanation from his Eminent Technology website.

Bruce has many patents and inventions including his unique air bearing tonearm, rotary subwoofer, vacuum platter as implenmented by SOTA, and many others.

Bruce Thigpen -

Reviewers have incorrectly attributed wow and flutter to the turntable. Since the advent of the belt drive turntable, wow and flutter has been purely a function of tonearm geometry, the phono cartridge compliance with the elastomeric damping, and surface irregularities in the LP. In our own lab we have measured many high quality turntables using a rotary function generator directly connected to the platters of the turntables.

The measured results are usually an order of magnitude better than the results using a tonearm and test record (conventional wow and flutter method). Further proof exists if you take two tonearms, one straight line and one pivoted and mount them both on the same turntable. The straight line tonearm will give a wow and flutter reading with the same cartridge/test record of about 2/3 to 1⁄2that of the pivoted arm (.03% < .07% to .05%). This is because the straight line tonearm has a geometry advantage and lateral motion does not result in stylus longitudinal motion along the groove of the record.

Another proof is to take two different cartridges, one high compliance and one low compliance, and take measurements with both using the same turntable and tonearm. The reading of wow and flutter will be different. All wow and flutter readings are higher than the rotational consistency of the turntable.