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Cartridge dynamic behaviour
Cartridge dynamic behaviour
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Old 17th April 2019, 05:31 PM   #1221
Hans Polak is offline Hans Polak  Netherlands
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I hope so.

I am more than grateful to Mogens

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Have lots of fun with it.


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Old 18th April 2019, 01:08 AM   #1222
scott wurcer is offline scott wurcer  United States
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Interesting result for the day. I tried the time slice method on the harmonics and got a similar result (as LD) on JP's file so I went back to my file where I let the 3150kHz tone on the Adjust + LP freely spin down from ~5kHz to 500Hz. The distortion was flat (pretty good BTW for my not so expensive Grado, ~-48dB 2nd's and ~-60dB 3rd's) which is interesting in that the stylus groove geometry would appear to be the sole cause of the distortion.
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Old 18th April 2019, 07:17 AM   #1223
gpapag is offline gpapag  Greece
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Cartridge dynamic behaviour
Very low distortion figures for vinyl.
At what level is this 3150Hz recording Scott?

George
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Old 18th April 2019, 08:28 AM   #1224
scott wurcer is offline scott wurcer  United States
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Very low distortion figures for vinyl.
At what level is this 3150Hz recording Scott?

George
IIRC -20dB so lowish.
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Old 18th April 2019, 10:12 AM   #1225
gpapag is offline gpapag  Greece
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Cartridge dynamic behaviour
OK, thanks

One in my "to be done" list is, to test the generator section of the cart for distortion vs level and vs freq

George
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Old 18th April 2019, 10:32 AM   #1226
luckythedog is offline luckythedog  United Kingdom
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Those HD figures seem plausible at that level IMHO.

LD
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Old 18th April 2019, 10:36 AM   #1227
Hans Polak is offline Hans Polak  Netherlands
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Originally Posted by scott wurcer View Post
Interesting result for the day. I tried the time slice method on the harmonics and got a similar result (as LD) on JP's file so I went back to my file where I let the 3150kHz tone on the Adjust + LP freely spin down from ~5kHz to 500Hz. The distortion was flat (pretty good BTW for my not so expensive Grado, ~-48dB 2nd's and ~-60dB 3rd's) which is interesting in that the stylus groove geometry would appear to be the sole cause of the distortion.
Interesting that the distortion remains stable while level drops when slowing down. The conclusions seems correct that the only cause can be the distortion in the record itself.
That however immediately raises the question how to interpret this test in other occasions like JPs recording.

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Old 18th April 2019, 12:02 PM   #1228
luckythedog is offline luckythedog  United Kingdom
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Originally Posted by Hans Polak View Post
Interesting that the distortion remains stable while level drops when slowing down. The conclusions seems correct that the only cause can be the distortion in the record itself.
That however immediately raises the question how to interpret this test in other occasions like JP’s recording.

Hans
In a spin down test of a monotone sine, geometric relationship between stylus and groove remains constant. For example pinch effect or tracking angle offset error. Velocity and cartridge output drops with rpm along with frequency, and harmonic distortion remains a constant fraction of fundamental level - in principle at least and that seems to be as Scott reports.

In contrast, JP's sweep is constant velocity. So geometry between stylus and groove changes as the groove shape becomes compressed along the linear axis with increasing frequency. Errors such as pinch effect and tracking angle offset error etc etc therefore increase with frequency, whereas fundamental level stays constant. And harmonic distortion increases as a fraction of fundamental level with increasing f.

The nature of the harmonic distortion law for the CV sweep is interesting and unexplained, whereas I think one can readily get that Scott's run-down sweep follows a flat law because stylus-groove geometry doesn't change. But that's an interesting observation in itself, because it means nothing else is in-play other than geometry.

Lastly, the synthetic sweep you generated doesn't show 2nd or 3rd harmonic distortion. And that's an interesting control test for JP's real sweep, because it shows the continuously shifting f doesn't introduce harmonic distortion itself - at least to any notable extent.

So this harmonic test method versus f is straightforward for CV sweeps, or for RIAA sweeps accepting that as it relates to constant programme level.

LD

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Old 19th April 2019, 04:38 PM   #1229
scott wurcer is offline scott wurcer  United States
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Here's my equivalent of LD's plot #1208. I used log/log but the basic wiggles seem to be close. The effective smoothing is different but I don't think it fundamentally matters, I notice a 6dB difference in the relative harmonic levels so I will use another program to calibrate and try to find where the discrepancy comes from. Even if we don't end up with a DIY test LP we can add this to our open source analysis package.
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File Type: png hplot.png (19.2 KB, 88 views)
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Old 19th April 2019, 07:25 PM   #1230
Hans Polak is offline Hans Polak  Netherlands
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Here's my equivalent of LD's plot #1208. I used log/log but the basic wiggles seem to be close. The effective smoothing is different but I don't think it fundamentally matters, I notice a 6dB difference in the relative harmonic levels so I will use another program to calibrate and try to find where the discrepancy comes from. Even if we don't end up with a DIY test LP we can add this to our open source analysis package.
Is it correct that looking at 10kHz, that at this point the 2nd at -33dB and the 3rd harmonics at -50db are belonging to the base frequency of 10kHz ?
In that case the second harmonic goes to 25kHz and the third to 16.7 kHz, right ?

Or do we have to read it differently and say the 2nd harmonic at 10kHz belongs to 5kHz base and the third harmonic at 10kHz to the 3k3kHz base ?

Assuming that the first one is true, I tried to match the distortion curve with an exponential curve.
Slightly adjusted from my earlier estimate, I have now used in the image below for the 2nd harmonic exp(freq/11800)/130 and for the 3rd harmonic exp(freq/7800)/1000.
Second going to 25kHz and the third to 16,7kHz.


Hans
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