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Turntable speed analysis part II

I'd like to see the Voyd again. I don't think the earlier recording does it justice.

OTOH I'm not at all sure that using the pink noise track is a good way to check RIAA correction...

Paul
 
I wasn't thinking of pink noise but the various sweep tones the UA disc has.

Hopefully I'll have another interesting recording to post here tomorrow from a very different deck to those looked at so far.
 
be handy for looking at the RIAA correction my new phono stage is applying.

Today's commercially available test LPs are woefully inaccurate in their noise tracks and/or spot frequency test tones and/or sweeps.

The best ways for measuring a phonostage are through a known-good (mind the parasitics!!!) inverse RIAA at the front, or else totally flat with low-noise capture and post-processing in a computer.
 
I do have a pretty accurate inverse RIAA, Sig Gen & Freq Meter I'd just be interested to see how the LP sweeps tally with it.
 
I can post the polar results from these if Paul doesnt mind. I think i have it to the point where they should be pretty comparable. What Dont have is a pretty way to display the FFT response data, just the polars.
 
edd, if I minded I would be wrong. More power to your elbow.

I'll process and post later this evening.

Paul
 
I didn't want to step on toes.

Here is the plot for the PL-71. Plotted with the last sample posted, I can see no real change.

pl71drag.jpg


Red is with drag, Green without.
 
I have no idea what to make of this one. The file was noisy, the result was noisy, I filtered it the same way as the PL-71.

guytest2.jpg


The spectrum is interesting as well, I will see what i can produce of it.
 
Interesting that it traces pretty much exactly the same path on each rotation, even though there is a lot of ripple.

I am still unsure on these. The polar plots show wow, ie under 10hz, very clearly. Is a very consistant 0.1 modulation at 6hz more or less important than say a consistant modulation at 50hz, or 100hz, that these plots may not show to well. I can't say I detect the similar speed variance on the Yamaha, but a golden ear I have not.
 
It is running slightly slow, 3Kz tone is centred at about 2991hz, noise floor looks pretty low, harmonics well surpressed

Sorry, the noise I was refering to was the resultant wow and flutter signal, and the plots were initially more noisy. I demodulated with a center frequency of 2992hz.
 
Ok, the noise, Is a regular spike, 5 times per revolution, It was clipping the output of the fm demodulation, probably explaining some of the sawtooth in the spectrum. the peak is around 20db higher than anything on any of the other turntables. I am still unsure if it is the file, the turntable, or a mistake I have made, probably the latter.
 


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