advertisement


Turntable speed analysis

Status
Not open for further replies.
Great! You find it in the links two posts above (post #78).
Would there be also some version of your software
available to the public (in exchange for pounds, euros, dollars, franks, etc)?
Thanks!
phixphi
 
I've processed the files and I'll get some pictures up tomorrow.

Anybody who wants the software is welcome to it, but I don't want to get into too much handholding and there are absolutely no guarantees...

I think your turntable may be running at 33.1rpm rather than 33.3...

Paul
 
Paul, I'll for sure be very interested. Thank you.
It might be that my deck ran a bit too slow. I'm wondering if the
930's strobo might be a bit off.
 
Paul R said:
I've processed the files and I'll get some pictures up tomorrow.

Anybody who wants the software is welcome to it, but I don't want to get into too much handholding and there are absolutely no guarantees...

I think your turntable may be running at 33.1rpm rather than 33.3...

Paul
Click to expand...

Hey Paul! I'm quite curious about your plots.
If you have a minute or two to post the results,
I'd greatly appreciate!
Thanks,
phi
 
I'll get active Sunday for sure. It's curious how your two test records differ...

Standby Andrew.

Paul
 
OK. Phix phurst.

The Clearaudio test disc recording is clipped and distorted. I've not seriously pursued it yet.

Reverting to the Ultimate Analogue, this is the tone itself,

Phix_UA_base.png


I think the wide multiple peak may be characteristic of this recording, it's certainly something to look into.

This is the wow spectrum,

Phix_UA_demod.png


The peak against the y axis is record eccentricity. The interesting peak at 2.74Hz, or 164rpm, is that the motor?

This is the polar plot, this shows speed irregularities that are regular with the platter rotation, so presumably generated by the mechanics of the drive.

Phix_UA_polar.png


I think this is better than the equivalent pre-repair plot but there is still evidence of a dent in the idler.

Paul
 
Now Andrew with an unidentified test disc.

This is the tone itself,

flat_3khz_base.png


This is the wow spectrum,

flat_3khz_demod.png


The first two peaks are probably record eccentricity and its second harmonic. I don't know what the Radikal motor speed is, there's nothing significant at 250rpm.

This is the polar plot.

flat_3khz_polar.png


Quite interesting. I wonder if the jaggediness is the notorious suspension wobble? There's no clear evidence for them in the spectrum. The regular deviations are at about the rate of the peaks at 8/9/10Hz in the second plot.

Repeating the recording with a locked suspension might be a very interesting comparison.

Paul
 
Paul! You are the guy, thank you!

Paul R said:
The Clearaudio test disc recording is clipped and distorted. I've not seriously pursued it yet.
Click to expand...

This very well may be my 155st preamp which has been very much out of the calibration
(and probably still is)

Paul R said:
Reverting to the Ultimate Analogue, this is the tone itself,

Phix_UA_base.png


I think the wide multiple peak may be characteristic of this recording, it's certainly something to look into.
Click to expand...

Again, this may be my preamp...

Paul R said:
This is the wow spectrum,

Phix_UA_demod.png


The peak against the y axis is record eccentricity. The interesting peak at 2.74Hz, or 164rpm, is that the motor?
Click to expand...

Ok, this is the idler. HM was mentioning that on his equipment (special test record with
brass insert for perfect centricity + probably one of EMT WF analyzers) he was seeing
an increase of W&F once per revolution. Perhaps the 2.74Hz peak and that once-per-rev. irregularity are correlated? Anyway, since the WF peak is below the EMT guarnteed specs, he has decided to leave it.

Paul R said:
This is the polar plot, this shows speed irregularities that are regular with the platter rotation, so presumably generated by the mechanics of the drive.

Phix_UA_polar.png


I think this is better than the equivalent pre-repair plot but there is still evidence of a dent in the idler.

Paul
Click to expand...

And how does the disc eccentricity manifest itself on this plot?
I mean how one can recognize where are the idler and the disc
contributions?

Great tool, Paul! Congratulations!
Phix

PS If you are still willing to share it, I'm definitely interested :)
 
And how does the disc eccentricity manifest itself on this plot?
Click to expand...
I think in a smooth deviation from roundness. The right half looks good, the left half has a corner in it.

If the reduction between the platter and the motor is 5:1 then I think we're also seeing eccentricity in the motor shaft.

It's worth remembering that being able to see things doesn't mean a fault, or 'badness'...

I'll upload the current state along with a readme. What I can't do is too much handholding, these are very much 'What if?' tools rather than production software.

Paul
 
Sondek was right, he will be pleased! lol.
Click to expand...
The right channel of Andrew's recording is much less jaggedy than the left. So it's more likely that the recording has a problem.

Sonddek is clearly wrong in his concept of dynamic wow, but there are other interesting factors.

Paul
 
I have a Pioneer PL71 (non quartz locked) DD here at the moment. I'd be interested to see what characteristics it exhibits, even if only from my ropey HFS69 test record. I'll try to upload a tone in the next day or two.
 
I think Paul has a recording of a tone from mine but the record I use is not the best.
 
Paul R said:
The right channel of Andrew's recording is much less jaggedy than the left. So it's more likely that the recording has a problem.

Sonddek is clearly wrong in his concept of dynamic wow, but there are other interesting factors.

Paul
Click to expand...

Or that the wobble is affected by the tonearm wire acting as a 'tie' more in one direction of wobble than another? ;-)
 
Paul R said:
I think in a smooth deviation from roundness. The right half looks good, the left half has a corner in it.

If the reduction between the platter and the motor is 5:1 then I think we're also seeing eccentricity in the motor shaft.

It's worth remembering that being able to see things doesn't mean a fault, or 'badness'...

I'll upload the current state along with a readme. What I can't do is too much handholding, these are very much 'What if?' tools rather than production software.

Paul
Click to expand...

Paul, I meant how do you make difference on the polar plot between record eccentricity, idler beat and motor shaft eccentricity? How do you recognize those factors on the plot?
To what would the dent on the left side correspond?
Obviously I agree that seeing things doesnt mean much (we are talking about hearing rather and the deck is said to meet EMT specs), but I'm very curious to learn how to use and interpret your plots, hence so many stupid questions :)) Sorry if too many. IIRC, the motor is around 1450rpm.

Best,
phixphi
 
My test disc is Decca SKL 4861 'How to give yourself a stereo checkout'

I'll record it again with the suspension locked (sticky tape) and 'free'.

Andrew.
 
Status
Not open for further replies.


advertisement


Back
Top