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Turntable speed analysis part II

phixphi said:
(#377) 0-50hz Standard
phix-standard0-50_zps8ccf4d7a.png


0-50hz Teflon
phix-teflon0-50_zpsbdb5e3ca.png
Click to expand...

I suspect those plots are created with a different amplification than the rest of the files I trid to compare: the 2.7Hz ideler fundamental is here at -33dB, while on the others is at -21dB -- -24dB.
The idea would be to use all the work done to figure out two things:

a) the influence of the console
b) the influnce of the teflon washers.

The best would be to try to organize the spectra in two groups above, taken and processed in the same way, save for the factor under examination (console, teflon). At my side the difference in the files potentially usefull for console/no-cosole comparison (quoted above in #437) is in the arm-cart---the tracks before #418 were taken with the native TSD15SPH in EMT929, from #418 on with FR7f in SME3012R, and I cann't easily change it right now so any comparison should take that into account, but still...
 
You can ignore the plot with the spike at 50hz, it should be at 25, that was due to the sample rate mix up.

Plotting the spectrum is the thing Paul is best at. I typically just look at in spectrum lab as I demodulate the file. It doesn't have an easy way to export the Spectrum.

I will get round to the files soon, but I suspect they are flawed. The difference in 0.55hz eccentricity peak is considerable, and it effects several of the other peaks, so even filtered out it will skew the results.

I suggest you get to grips with spectrum lab, and the files it produces, to verify the recordings are closely matched in speed, and eccentricity.
 
Here are the wave forms:
eccentricity_zpsff872206.jpg


0, the eccentricity is severe, 2 is high, 1 and 3 are ok. 0, 1 and 2 are running slightly slow, 3 is running slightly fast.
 
edd9000 said:
I will get round to the files soon, but I suspect they are flawed. The difference in 0.55hz eccentricity peak is considerable, and it effects several of the other peaks, so even filtered out it will skew the results.
Click to expand...

Ed, thanks! If you plot them at the same scale, I'll try to use some graphical programme to change colors and supreimpose them.
As for the eccentricity, the UA disc has a huge center hole with a lot of a play---each time I changed something the LP was centered
differently, hence the difference in the 0.555 peak. But I'm surprised you think it should affect the other peaks,
why would it? Some sort of an intermodulation?
 
I've been very busy with work and with a recalcitrant Buffalo DAC I need for this weekend's Hifi Show at Scalford. I'll process phix's latest early next week and see what's what.

I created an FFT app some time ago, but it's a bit arcane. It's capable of doing very big FFTs, 2^24 points at least and applying various windows. Input is raw binary doubles or long doubles, output is text suitable for GNUPlot.

Paul
 
Paul R said:
I've been very busy with work and with a recalcitrant Buffalo DAC I need for this weekend's Hifi Show at Scalford. I'll process phix's latest early next week and see what's what.
Paul
Click to expand...

Would be great! Have a good show.
 
In the meantime I have invested 5EUR into unlocking IEC 386 wow measurement in the Android Platerspeed and checked my recent files from #436. 35s samples with a 0.555Hz notch filter (Feickert calls it IEC386 2-sigma) the lowest wow at 0.06%-0.07% (depending on the run) is when the bottom washer is present only (1'). The standard gives 0.09-0.1%, top washers 0.08-0.09%, all washers 0.08%

IF those measurements have any meaning, then it would be quite counterintuitive: the idler travels upwards on it's axis during the rotation, so it works against the upper locking washer rather than the lower one (with a pin). However puting the teflon below reduced wow by 1/3 rather than above...go and figure...
 
Are you making some assumption about where the difference comes from in each measurement? Could there be more than one variable at play, friction, idler height, angular offset potential, tension of locking nut......?
 
sq225917 said:
Are you making some assumption about where the difference comes from in each measurement? Could there be more than one variable at play, friction, idler height, angular offset potential, tension of locking nut......?
Click to expand...

Sq, all files were taken at the same run, after 1h+ warump, under the same ambient cond. I do not think there are really different variables in the play apart from the teflon + LP centering--there is very little I could possibly change (see below). The top clip washer (not a nut!) has no way to adjust--it just clips into the idler spindle groove and that's it. It's something like that:

http://www.gasgoo.com/auto-products/universal-parts-301/1288821.html

and I think I've erroneously called it a "locking washer". Sorry. Angular offset is the holiest cow I do not dare to touch after the EMT service (I've been exchanging all the washers very gently, trying not to push the idler much, it sits at ~3.5mm steel spindle fixed to a ~4mm steel plate..not easy to bent).

The teflon is +/- 0.3mm so the idler position is changed by 0.6mm at max (two teflons on top) and it's vertical travel by at max 0.9mm (all there teflons in place). What I suspect is that the idler travels upwards, bounces back and goes downwards, touching the bottom fiber washer, then going up again etc. This is based on an observation that with no smoothing teflon washers, the clip washer on top is periodicaly engaged in the rotation (the idler pressing it from below, when reaching the top position?) and then disengaged (the idler traveling downward and probably working against the lower fiber washer?). With the teflon below the idler only, this still happens but much rarely--the clip washer is most of the time engaged in the rotation, stopping only occasionaly for a very short time. This is probably due to the added 0.3mm at the bottom, limiting the idler vertical travel. If what I measure is credible, if, than this means that smoothing the idler work against the bottom fiber washer (as per the original trick by the Lencoheaven Dmitri) is more important than smoothing the work agianst the upper clip washer. What I may try is adding a second teflon on bottom, netting in 0.6mm limiting of the idler vert. travel.

Here is a pic of the idler, with the top fiber & clip washers clerly visible:

http://www.mediafire.com/?u4whr2bzav8n09h
 
My SL1200, HFN test disc, better disc on its way. So unsure how valid this is.

sl1200polar_zps3640ee31.jpg


The spikes look to be the speed correction.
 
Not necessarily, is the radial scale calibrated? The glitches could also be artifacts of noise on the test record
 
I'm going to hold off judgement or further poking until the new test disc comes. I ordered the one from platterspeed. I left my analogue productions one in the states, it will be interesting to compare a 3rd disc.

I can calibrate the radial scale by overlaying circles of a set deviation, I'll do that on the next one.

These plots are very sensitive, I did some number crunching at one point trying to produce some form of decimal percentage, but it was usually within specification or lower.
 
Edd if you are UK based you can borrow my AP test record. Most of the samples on this thread were from my record so you'll have a comparative base.
 
I am back in the UK, but I was intending on having my AP record brought back by the next visitor from Florida, so I wouldn't worry about it.


If any of the other Dr.Feickert products are to go by, the test disc should be a good one.
 
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