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Turntable speed analysis

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Paul, and the 4.38Hz and 5.56Hz you've mentioned in the first post?
They don't seem to appear on the spectrum plot.
25Hz...I don't know, but all my syndromes seemed to point to the motor.
This frequency appeared at the moment stylus got in contact with the record,
irrespectively of the track.

If I may, I'd strongly encourage you to make an attempt
at an advanced software w&f meter. Perhaps loaning a
good analog w&f meter for checking the software would
be an option.

Cheers,
jk
 
Hi Paul

You may know who I am? Amongst other things it was I who challenged Paul Miller's tests in Hi Fi World a month ago! My test gear is here http://www.soundhifi.com/test.html old but perfectly good.

My own tests on a SL-1200, SP-10 and Michele Gyro had indicated a variety of issues, and none that appeared to be discussed out in the open. So thanks to Guy from Puresound to alerting me of this thread.

I have performed similar tests by taking the FM demodulated 3.15Khz from a Clearaudio test record from the FL-180A and analysing the spectrum of that using the 3561A. This is messy but does work in real time.

Is there software available that will do this in one hit?

Regards

Dave
 
Cool, can we see the measurements for the improvements wrought over the basic 1210 for your own Timestep power supply then Dave. Everyone would love to see them.
 
The PSU does many things, not only motor performance. I'm not here to advertise, or even allowed to. I simply want to converse on flutter measurement and this is what this thread is all about.

Dave
 
5-15.jpg


Kevin Pyne a local Dartmouth poet once said " if you want to sit by the fire, now and again you have to get up and put a log on it " He was referring to newcomers to the town. So here is my log; a FM demodulated plot of 3.15Kz. It shows a big peak at 6.6667 Hz and a shed load of .555hz sidebands.

So the question is, are the wow sidebands real or an artefact? That's why I would like to try a software implementation.

Regards

Dave
 
Dave,

I read a DSP book and built a program that takes a mono wav and FM demodulates it. I have another program that performs a high resolution FFT. The output can then be graphed with (for example) GNUPlot, which is where all the pictures I've posted came from. This is rather adhoc and unfinished. They are definitely not products in any way...

You're welcome to have a go or if you send me a recording I can process it. It's on my list to hone the software somewhat, allow stereo inputs for instance. And to optionally narrow band filter about the test tone frequency. But primarily to check the results are correct.

Paul
 
Amongst other things it was I who challenged Paul Miller's tests in Hi Fi World a month ago!
I don't see the magazines very often, is this something worth searching out?

Paul
 
I don't see the magazines very often, is this something worth searching out?

Paul

Not really. There was an interesting enough feature about the SP10 and some 'measurements' which appeared to be very similar to those taken from a Garrard in an earlier edition. Given that the noise generated by each of these turntables might be expected to differ somewhat in character, it was suggested that the noise measurements made were not terribly relevant. The response was along the lines that they were both sorta direct drive so the similarity was unsurprising.
 
Hi Paul, Yes please, how do I try the software? Can you filter it first before demodulating? And then apply filtering before the FFT? I'm looking solely for flutter at the moment. How long does the software need to analyse for? Doing it in real time takes nearly a minute.

sq225917 Your last post was removed, obviously you didn't get the message? Please don't respond to any of my posts, including this one.

Guy, thanks for explaining that. I hadn't expected my e-mail to be included as a letter, and haven't seen the magazine. But yes, I noticed that if you took the wow/flutter spectrum of two dissimilar turntables and superimposed the plots in Photoshop, they were unfeasibly similar.

Tony, thanks for letting me talk technical here.

Regards

Dave
 
Hi Paul

I've slept on it! Could I try your FM demodulator software please?

Also, could you do a plot from 5 - 15Hz of Guy's SP-10 please?

Thanks

Dave
 
Hi Dave,

Have been attempting to get meaningful measurements of W/F using an Leader LFM-39A and Uwe Muller's audioTester software using the 3.15kHz track from the ultimate analogue test LP but it seems that the measurements are limited due to failure to successfully eliminate eccentricity of the test LP in spite of using an outer ring weight from Canada(TTweights) that centres with a machined acrylic platter.

I've been more successful using both methods and Luis Peromarta test tapes on my Nak Dragon and Revox B215s tape decks. In fact it helped me finding pinch rollers(set from Italy; avoid german ebay rollers, they're rubbish) for the Revox that got W/F close to Dragon levels. Unfortunately, only after I had dismantled the drive to re lubricate, which is not for the faint hearted:).

To be honest, I got more variation in results from eccentricity than I could demonstrate by changes to the electronics on my SL1210 and the belts/motors on my belt drive turntables.

Anyway, I wish you good luck in trying to solve this challenge.

BW
Cornelius
 
Hi Cornelius

Well, I have a Leader LFM-39A as a spare. But I'm not sure that Paul's software isn't better, or could stand some pre-filtering?

I agree on wow, and except for really old designs, I think the record eccentricity far outweighs the turntables wow. However flutter is an entirely different mater. Even oil viscosity can have an effect. But how to make a "repeatable" measurement is the quest? We need to remove every trace of 0.555Hz and only look at the real flutter/speed-instability.

I beginning to think a really close analysis of the actual 3.15Khz itself might be possible?

Whatever, I never seem to have enough time to do everything I think off?

Regards

Dave
 
Dave,

I'm doing some tinkering to make it less finicky. I'll update this thread later or tomorrow.

I'm not convinced that the recording I have of Guy's SP10 is really representative, I think his test record is more variable than the turntable. I have the Analogue Productions test record and an SP10 that may or may not be 'fit'. I'll generate some data anyway.

Paul
 
Hi Paul and the rest!
I'm not sure if the project is still active, and if you'd be intererested in more
data for the analysis, but I've finally found time to record
the w&f test tracks of EMT930 after the authorized repair.
Here they are, the same Test LP as before (UltimateAudio) and the Clearaudio Trackability:

http://www.mediafire.com/?aadsdd4walc4os6

http://www.mediafire.com/?k95shupco8i21qz

I'd for sure love to see your analysis now and compare to what it was.
Cheers,
jk
 
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