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,