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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 12th March 2010, 07:15 PM   #3881
john curl is offline john curl  United States
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Don't worry Joachim, my granddaughter will do in a pinch. ;-)
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Old 12th March 2010, 08:29 PM   #3882
Joachim Gerhard is offline Joachim Gerhard  Germany
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Yes, Girls have even better ears.
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Old 13th March 2010, 05:23 PM   #3883
simon7000 is offline simon7000  United States
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Originally Posted by Joachim Gerhard View Post
I hope you find a good one that is not so expensive.
What values do you use in the Bulk metal resistors?
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Old 13th March 2010, 05:50 PM   #3884
john curl is offline john curl  United States
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I don't know yet, Joachim. Anything from 5 ohms to 50K, I would presume.
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Old 13th March 2010, 06:58 PM   #3885
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by john curl View Post
About 25 years ago, I compared Corning Grey resistors with Corning Green and Blue resistors. I had the help and advice of a promising colleague, Scott Wurcer, in doing so, because he showed me how to make a adaptor for my Quan-Tech Noise Analyzer so that it could measure EXCESS noise. Green and Blue resistors were distinctly inferior with 10V DC applied to them, compared to the Corning Grey. This is but one difference, but at least it was measurable.
I forgot about that, did I send you the excess noise schematic? I think I still have the schematic from the adaptor board. Probably useful to all of 10 people in the world.
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Old 13th March 2010, 07:17 PM   #3886
Joachim Gerhard is offline Joachim Gerhard  Germany
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I use 300 Ohm and will try 138 Ohm on the High Z MPP. 1kOhm was still too treble heavy in my system.
John, a wirewound pot should work well for cartridge loading. It has vitually no excess noise.
RS Components make a presision one. I could try to find it.
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Old 13th March 2010, 08:57 PM   #3887
simon7000 is offline simon7000  United States
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Quote:
Originally Posted by Joachim Gerhard View Post
I use 300 Ohm and will try 138 Ohm on the High Z MPP. 1kOhm was still too treble heavy in my system.
John, a wirewound pot should work well for cartridge loading. It has vitually no excess noise.
RS Components make a presision one. I could try to find it.
If you PM me you shipping info I should be able to send you some 300 and 138 ohm samples of the more cost effective resistors that measure well.

If any one wants to they have my permission to re-post the attachment to this thread in a PDF format. ES
Attached Files
File Type: doc Reference Resistor Test.doc (68.5 KB, 73 views)
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Old 13th March 2010, 09:06 PM   #3888
Joachim Gerhard is offline Joachim Gerhard  Germany
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That one works quite well.
http://docs-europe.origin.electrocom...6b805e0fa8.pdf
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Old 13th March 2010, 09:35 PM   #3889
1audio is offline 1audio  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 forgot about that, did I send you the excess noise schematic? I think I still have the schematic from the adaptor board. Probably useful to all of 10 people in the world.
Being one of those 10 people please forward it. Not that I need it for resistors, I have the resistor analyzer and the Semi analyzer's noise floor is too high for low value resistors. But it may be useful for testing Zeners and voltage references.
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Old 13th March 2010, 09:41 PM   #3890
1audio is offline 1audio  United States
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John Curl's Blowtorch preamplifier part II
Excess noise-
is the noise generated by passing DC at some level of power dissipation through a resistor. I don't see how it can be an issue with a phono input. Most cartridges woould be a smoking ruin before there was enough DC to generate noise in the loading resistor.
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