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26th March 2019, 11:27 AM  #941  
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Join Date: Nov 2009
Location: London, UK

Quote:
LD 

26th March 2019, 12:01 PM  #942 
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Join Date: Jan 2004
Location: Belmont MA

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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26th March 2019, 12:57 PM  #943 
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Location: Blaricum


26th March 2019, 01:50 PM  #944  
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Quote:
George
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["Second Law is a bitch."  SY] ["I insist on respecting the means of the average person working in their garage/basement." Scott Wurcer] 

26th March 2019, 03:39 PM  #945 
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26th March 2019, 04:44 PM  #946 
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Thanks
George
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["Second Law is a bitch."  SY] ["I insist on respecting the means of the average person working in their garage/basement." Scott Wurcer] 
27th March 2019, 09:40 AM  #947  
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Join Date: Nov 2009
Location: London, UK

Quote:
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 f^{2}. So those graphs look plausible in principle, I think. LD 

27th March 2019, 10:09 AM  #948 
diyAudio Member

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. 
27th March 2019, 12:16 PM  #949  
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Join Date: Nov 2009
Location: London, UK

Quote:
LD 

27th March 2019, 01:34 PM  #950  
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Join Date: Mar 2005
Location: Blaricum

Quote:
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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