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Turntable speed analysis part II

edd9000 said:
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.
Click to expand...

It is not a good one. The Feickert test LP has significant and inherent speed errors (I have it and was for a while puzzled why all my turntables showed the same speed variation pattern).
 
Shuggie said:
It is not a good one. The Feickert test LP has significant and inherent speed errors (I have it and was for a while puzzled why all my turntables showed the same speed variation pattern).
Click to expand...

Oh well, I was after one anyway as the current one is well worn and 3khz not 3150hz.

In the case of these polar plots the analogue productions speed errors often over shadow that of a turntable, but to me, if our turntables are revealing the errors on one of the best lathes, then the turntable is doing a good job.
 
Well here is the polar from the Dr Feikert test disc. Gone are the spikes but I could be convinced the shape and pattern is similar.

sl1200polar2_zps25905305.jpg


The spectrums show no correlation other than a small spike at 13.3hz which correlates to 24 times per revolution, probably tied to the 12 pole motor or its sensors.
 
For reference here are the last 2 plots with a 0.1% modulation. The 0.1% modulated tone varies the 3150hz signal between 3120hz and 3180hz.

sl1200polar-0_1_zps2721338a.jpg


sl1200polar2-0_1_zps6c59780c.jpg


Doing an RMS on the values from sox and comparing to the known 0.1% file, I get an rms value of 0.88%. Completely incomparable to standard measurement equipment because I cant easily duplicate the weighting.
 
sq's Kuzmaesque with Geddon update and drag,

sq_geddon_recap.png


and polar,

sq_geddon_recap_polar.png


It's nice to see the recording's flaws show up consistently. I think the demodulated spectrum shows an improvement in the artifacts around the motor speed. The three red peaks between 4Hz and 6Hz are at effectively 250rpm, 300rpm and 333rpm(!). The polar looks smoother or at least more consistent. The speed has dropped by about 0.4%.

Paul
 
No, it's with a 24V AC synchronous motor - the same that Rega use.

As Paul says, the bearing is viscous coupled - also magnetically supported and driven by a power supply that is quite unlike the Armageddon.
 
edd9000 said:
I did a bit of looking into it, the Analogue productions test lp was cut on a Neumann VMS 80 at sterling sound.

On here:http://sterling-sound.com/mastering/vinyl/#3

And I quote "The VMS 80 computer divides each rotation of the platter into sixteen increments"

16 increments works out to be 8.88hz, visible on most the spectrums, particularly the Yamahas. It also showed up on my DIY turntable plot.
Click to expand...

Interesting as those 16 increments seem to be very clearly shown in the plot below and that was made using the Analogue Productions test record.

26657205396_11468af48f_b.jpg
 
sq225917 said:
Interesting that the cutting lathe shows through, I often thought the record less than ideal
Click to expand...

Pretty much why I gave up caring. The test lp was cut by the best process and people going. No music lp is going to be any better. Once the TT is as good as the lathe, job done.
 
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