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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 14th May 2010, 12:02 AM   #4341
scott wurcer is offline scott wurcer  United States
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Bruce Brisson, those MIT white papers are full of zingers. Random reactive noise RRN, a reactance has no real part to its impedance and can not generate noise. Even you can't argue with that.
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Old 14th May 2010, 12:25 AM   #4342
john curl is offline john curl  United States
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Anyone who actually studied one of his cables would find it different in construction geometrically from typical cable, but his materials are just typical for average audiophile cables. VDH's cables are made of much better materials and insulation, but have very nominal geometries, more like normal cable. Go figure!
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Old 14th May 2010, 07:23 AM   #4343
john curl is offline john curl  United States
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It is difficult to understand what really happens at very low voltage levels in a cable. We do know that impurities and micro-cracks change the optimum resistance of a particular metal slightly at room temperature and a lot at very low temperatures, as this is the residual 'resistance' that reduction in temperature will not reduce correspondingly. But is it actually 'resistance' or is it micro-gaps and diode like components? Who knows? I don't for sure, and no textbook that I have ever found tells me specifically.
If VDH is right, then it is important.
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Old 14th May 2010, 11:56 AM   #4344
Joachim Gerhard is offline Joachim Gerhard  Germany
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I could ask Jürgen Ultee if measurements have ever been done. He works with Van den Hul.
 
Old 14th May 2010, 01:54 PM   #4345
scott wurcer is offline scott wurcer  United States
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How come the issue of Barkhausen noise never (rarely) comes up in audio?
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Old 14th May 2010, 02:12 PM   #4346
Joachim Gerhard is offline Joachim Gerhard  Germany
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I think Jean Fadel in France looked into that. He makes cable under the name Fadel Art.
I know the effect from coils and usually use high quality ferrite instead of iron to avoid it.
 
Old 14th May 2010, 02:20 PM   #4347
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by scott wurcer View Post
How come the issue of Barkhausen noise never (rarely) comes up in audio?
Lost (forgotten) knowledge
 
Old 14th May 2010, 02:36 PM   #4348
simon7000 is offline simon7000  United States
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Quote:
Originally Posted by scott wurcer View Post
How come the issue of Barkhausen noise never (rarely) comes up in audio?
I suspect it does, just the name is lost. Iron bearing chassis are thought to sound bad, capacitors with copper plated steel leads are also on the "parts to avoid list."

One recent grad working for me had a theory, that he didn't need to know the old stuff. He was only interested in what was new! His college changed the curriculum so they never graduate someone so ill prepared again! (TRUE STORY)
 
Old 14th May 2010, 05:55 PM   #4349
john curl is offline john curl  United States
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Jan, the question is whether VDH EVER did the test that he claims, as VDH gave specific results in print. No, he did not write a peer-reviewed paper, like I asked him to do for the IEEE, but the detail that he gave me, more than 25 years ago, was enough to convince me that he did the test.
It would be similar to asking me if I ever did a sine-square TIM test, myself, on all my amp designs, since 1978, I haven't. It is just too hard to do on a general basis and is hard to calculate a 'number' to correspond with a quality factor. Still, I can easily predict the results of future designs, based on measuring previous designs, and noting the trends that promote TIM, such as slew rate.
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Old 14th May 2010, 06:37 PM   #4350
stinius is offline stinius
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Hi John

What about Group Delay?
I think that is an interesting topic, especially in global feedback designs.

Cheers
 

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