John Curl's Blowtorch preamplifier part II - Page 3155 - diyAudio
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Old 18th December 2012, 12:11 AM   #31541
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Originally Posted by bcarso View Post
But whether even it is significantly better overall, given the other noise sources like Brownian motion of air and thermomechanical noise of the structure of the capsule is questionable.
Well I do have a small interest in capsule design.

With evil 21st century digits, it's possible to re-visit some of the compromises we had to make in da previous millenium. Excuse me for swearing
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Old 18th December 2012, 02:52 AM   #31542
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Originally Posted by bcarso View Post
The 862 is fine except for the rather high current, given one of Scott's constraints being battery operation. But whether even it is significantly better overall, given the other noise sources like Brownian motion of air and thermomechanical noise of the structure of the capsule is questionable.

Which reminds me: I wonder if Wave ever tested those photonic mic capsules?
2SK222 of Sanyo is the best because the Idss is only around 1mA. There is no need to run a FET in a mic at Idss so this does not matter anyway.

In any case I stated my case in my articles and have tired of correcting the misconceptions. The JFET in a large capsule mic has little or nothing to do with the noise performance. The obsessive Neumann rebuilders search for authentic 1960's 2N3819's for goodness sake.
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Old 18th December 2012, 02:54 AM   #31543
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Originally Posted by wayne View Post
That Sony looks very nice shame you can't get them.
I would bet that you could.

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Old 18th December 2012, 03:13 AM   #31544
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Originally Posted by wayne View Post
That Sony looks very nice shame you can't get them.
Try this 2sk152 Sony FET 15V .05a .3W DSG | SONY *SS | Distributed By MCM at 1.52 or 147 for four each .
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Old 18th December 2012, 04:36 AM   #31545
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2SK150.
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Old 18th December 2012, 05:04 AM   #31546
RNMarsh is offline RNMarsh  United States
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Originally Posted by Esperado View Post
Mr Marsh, Error correction works in comparing two signals. I am afraid there is noway to use that kind of thing on an oscillator, where there is nothing to compare.
I was hunting for something along the lines as conceptual... --- Demian has suggested the method Amber uses which phase shifts the harmonics and feeds it back somewhere/how to cancel them. I'll look into that. Thx-RNMarsh

Last edited by RNMarsh; 18th December 2012 at 05:15 AM.
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Old 18th December 2012, 05:14 AM   #31547
RNMarsh is offline RNMarsh  United States
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Default 2SK152

The 2SK152 device may still be around... just have to go to Texas to get it at InterFET Corp. They say the 2SK152 is same process as their IF1320 and IFN152. Also, same process as 2N6451,2,3,4 (process NJ132L). Thx-RNmarsh
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Old 18th December 2012, 05:38 AM   #31548
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Originally Posted by RNMarsh View Post
I was hunting for something along the lines as conceptual... --- Demian has suggested the method Amber uses which phase shifts the harmonics and feeds it back somewhere to cancel them. I'll look into that. Thx-RNMarsh
The two problems i had encountered with this kind of cancellation is both phases and levels. Hard to be better than 60db in the best situations (low frequencies <1000Hz).
I used this kind of canceling circuit to evaluate dynamically (With musical signals) the distortion of amps (and listen to-it). It is the base of my protection circuit.
Levels are hard to set too.
Did-you want to design an analog distortiometer ?
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Old 18th December 2012, 05:45 AM   #31549
RNMarsh is offline RNMarsh  United States
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Originally Posted by Esperado View Post
The two problems i had encountered with this kind of cancellation is both phases and levels. Hard to be better than 60db in the best situations (low frequencies <1000Hz).
I used this kind of canceling circuit to evaluate dynamically (With musical signals) the distortion of amps (and listen to-it). It is the base of my protection circuit.
Levels are hard to set too.
Did-you want to design an analog distortiometer ?
I'm trying to get the oscillator in an HP339A as low in H2 and others as is humanly possible. It allows for multiple freq and the built-in analyzer is a bonus (I have picked up an ShibaSoku AD725D anaylzer). They use a jFEt for agc and it is the limitng factor -- espec H2. Thx-RNMarsh
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Old 18th December 2012, 06:00 AM   #31550
RNMarsh is offline RNMarsh  United States
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FYI -- anyone else buy one of those nano scopes? i just got one (4 channel DSO: DS203) cause its so cute. And, it takes up zero space on the crowded work bench and good for following a signal around to see where it gets lost or goes wrong. Size of deck of cards and 1/2 the thickness. Nice color display rez, too. USB and signal gen port output. www.minidso.com -RNM

Last edited by RNMarsh; 18th December 2012 at 06:10 AM.
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