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Cartridge dynamic behaviour
Cartridge dynamic behaviour
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Old 26th March 2019, 11:27 AM   #941
luckythedog is offline luckythedog  United Kingdom
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Originally Posted by Hans Polak View Post
But now it comes: When making the same speed step with a mono signal, level deviation becomes zero !!!

So a stereo signal seems to increase its level with the sqrt of the speed increase factor whereas mono has a direct proportional relation.
It's a pity Faraday doesn't live anymore, he could have helped us.
There is a systematic error here, Hans. I cannot imagine what that is, but it cannot be real for reasons set out previously.

LD
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Old 26th March 2019, 12:01 PM   #942
scott wurcer is offline scott wurcer  United States
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Originally Posted by luckythedog View Post
There is a systematic error here,
Yes, I let the first track (3150Hz speed calibration tone) on the Adjust + spin down freewheeling from 5kHz to 640Hz and saw no issues.
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Old 26th March 2019, 12:57 PM   #943
Hans Polak is online now Hans Polak  Netherlands
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Originally Posted by luckythedog View Post
There is a systematic error here, Hans. I cannot imagine what that is, but it cannot be real for reasons set out previously.

LD
Hi LD,
Read on, after this posting I discovered that it had to do with RMAA.
So I took this all back in #933.


Hans
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Old 26th March 2019, 01:50 PM   #944
gpapag is offline gpapag  Greece
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Cartridge dynamic behaviour
Quote:
Originally Posted by Hans Polak View Post

In the meantime Maxim has already given a superfast reaction, and the problem seems to be solved.
I'm back again in business with RMAA.
Hans, can you inform us how the problem has been solved? (me too I am using RMAA)

George
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Old 26th March 2019, 03:39 PM   #945
Hans Polak is online now Hans Polak  Netherlands
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Originally Posted by gpapag View Post
Hans, can you inform us how the problem has been solved? (me too I am using RMAA)

George
Hi George,

Problem solved, I did something wrong.
You can continue using RMAA without worries.


Hans
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Old 26th March 2019, 04:44 PM   #946
gpapag is offline gpapag  Greece
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Cartridge dynamic behaviour
Thanks

George
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Old 27th March 2019, 09:40 AM   #947
luckythedog is offline luckythedog  United Kingdom
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Originally Posted by gpapag View Post
Thanks Demian
I added Demian’s cartridges data into the previous diagrams from my measurements for comparison.
Thank you, George.

I admit I've lost track of the test jig/regime in play here, would you pls briefly outline?

On the face of it, these results across a range of cartridge coils show strong f dependent loss / f dependent inductance which I suppose shows up as the coil impedance becoming more real at hf, especially above the audioband?

Generally in magnetics, there has to be a time derivative involved for there to be any action. Such as rate of change of flux, ie velocity. The effect of constant amplitude sine f sweep is that velocity increases directly with f (the derivative of sin(at) is a*cos(at).

Loss mechanisms that involve flux reversals also depend directly upon the derivative of number of reversals, ie frequency (reversals per second).

So magnetic loss mechanisms should have a direct f relationship as the lowest observable order. If two independent mechanisms apply, the lowest order should be f2.

So those graphs look plausible in principle, I think.

LD
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Old 27th March 2019, 10:09 AM   #948
billshurv is offline billshurv  United Kingdom
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Cartridge dynamic behaviour
I'm having trouble interpreting that post. If you are saying that the cartridge coils show the usual frequency response and resonant peak associated with a real world inductor then I agree.



What interests me is that we have an inkling of a credible mechanism for the midband droop in MMs that doesn't require jumping through the hoops of mech resonance in the audioband.
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Old 27th March 2019, 12:16 PM   #949
luckythedog is offline luckythedog  United Kingdom
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Originally Posted by billshurv View Post
I'm having trouble interpreting that post. If you are saying that the cartridge coils show the usual frequency response and resonant peak associated with a real world inductor then I agree.
Well cart coils should behave as real world inductors. I was trying to say some loss dmechanisms depend on rate of change of flux which is only a cousin of frequency. Also on level. So periodicity as in sine f isn't necessarily involved. Whereas some mechanisms are periodic such as LC resonance or hysterisis loss.

LD
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Old 27th March 2019, 01:34 PM   #950
Hans Polak is online now Hans Polak  Netherlands
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Originally Posted by scott wurcer View Post
Yes, I let the first track (3150Hz speed calibration tone) on the Adjust + spin down freewheeling from 5kHz to 640Hz and saw no issues.
Scott,

It took me quite some time to get results to within +/-0.5dB while performing this test.
I used the same methodology as before, and calculated the level curve, as well for a square law as for a direct proportional relationship between speed and level.

In the image below the two calculated curves are drawn, together with the measured curve.
Deviation of only +/-0.5dB from the calculated curve proves two things:
1) level is directly proportional to speed
2) the math used to predict this seems to be accurate.


Now I'm still faced with the problem why for all the other measurements, six in total, level has to be corrected by exactly 10*log(speed change).

Hans
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