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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 29th December 2012, 11:57 AM   #31901
dimitri is offline dimitri  United States
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Quote:
If you want to be helpful, find the equation for distortion from a mike capsule with a varying capacitance under vibration against a fixed load capacitance.
Here are the measurement results from bktr79-4
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Old 29th December 2012, 12:08 PM   #31902
scott wurcer is offline scott wurcer  United States
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John Curl's Blowtorch preamplifier part II
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Here are the measurement results from bktr79-4

I think this is what John wants. B&KTR 96-1

Reduction of Non-linear Distortion in Condenser Microphones by Using
Negative Load Capacitance .................................................. .................... 19
by Erling Frederiksen

It contains a full mathematical derivation of distortion as related to load capacitance, with verification by mechanical measurements.
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Old 29th December 2012, 12:20 PM   #31903
scott wurcer is offline scott wurcer  United States
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John Curl's Blowtorch preamplifier part II
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Once again: This is WHERE I got my first insight. Mead got it from earlier work, so what?
Johnson's derivation of the noise of an RC network is taught by sophomore year, so what?
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Old 29th December 2012, 12:26 PM   #31904
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
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Originally Posted by scott wurcer View Post
I think this is what John wants. B&KTR 96-1

Reduction of Non-linear Distortion in Condenser Microphones by Using
Negative Load Capacitance .................................................. .................... 19
by Erling Frederiksen

It contains a full mathematical derivation of distortion as related to load capacitance, with verification by mechanical measurements.
You can find this paper included in Technical Review 1 (1996), "Calibration Uncertainties & Distortion of Microphones," available on B&K's site.
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Old 29th December 2012, 12:46 PM   #31905
john curl is offline john curl  United States
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Thanks Dimitri, I knew you could come through!
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Old 29th December 2012, 01:01 PM   #31906
john curl is offline john curl  United States
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There is an equation around somewhere as well. That is what I was first looking for, but the GRAPH that you found, Dimitri SAYS IT ALL! Thanks.
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Old 29th December 2012, 01:17 PM   #31907
john curl is offline john curl  United States
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Please note dynamic input resistance and capacitance of B&K mike preamp:
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Old 29th December 2012, 01:51 PM   #31908
Telstar is offline Telstar  Italy
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Lavry paper applies only to sigma-delta conversion.
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Old 29th December 2012, 06:22 PM   #31909
john curl is offline john curl  United States
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Here is another important graph:
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Old 29th December 2012, 09:19 PM   #31910
Wavebourn is offline Wavebourn  United States
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John Curl's Blowtorch preamplifier part II
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Wavebourn, resistors have capacitance too. Earling Fredrikson told me himself that this was the reason when I visited B&K in 1974.
However, if they were dealing with high parasitic capacitance of resistors, they were right. Were they multilayer?
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