John Curl's Blowtorch preamplifier part II - Page 2722 - diyAudio
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Old 3rd September 2012, 08:09 PM   #27211
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Chris, for the record, different jfet selections are really not necessary, IN THIS SCHEMATIC. However, in my Constellation schematics, I use different MANUFACTURERS of the jfets.
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Old 3rd September 2012, 08:13 PM   #27212
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Be careful of mumetal, however, or even steel, as a shield.
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Old 3rd September 2012, 08:20 PM   #27213
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Aluminum only, or non-magnetic stainless steel.
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Old 3rd September 2012, 08:21 PM   #27214
morinix is offline morinix  United States
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Quote:
Originally Posted by Pano View Post
This isn't a preamp build thread. That should have been obvious twenty thousand posts ago. It's a discussion of audio design, more or less.

Build threads are great, this just is not one of them.
That is what it is now but it started as a simple request for a schematic to add to a library.
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Old 3rd September 2012, 08:37 PM   #27215
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Originally Posted by john curl View Post
Ken, the IC's are SERVOS and work below the audio bandwidth.
Duh, stupid me. I somehow overlooked the obvious integrating caps. in those op-amp's feedback loop.
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Old 3rd September 2012, 08:51 PM   #27216
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Quote:
Originally Posted by john curl View Post
Aluminum only, or non-magnetic stainless steel.
How about copper, or silver plated copper?
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Old 3rd September 2012, 08:58 PM   #27217
bcarso is offline bcarso  United States
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How about copper, or silver plated copper?
Cu is great but difficult to machine and very expensive thus.
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Old 3rd September 2012, 08:58 PM   #27218
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Originally Posted by john curl View Post
Aluminum only, or non-magnetic stainless steel.

Mr. Curl, is that because steel or ferric metal can be excited into being a magnet in the presence of a magnetic field...thereby fixing one problem and spawning others?
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Old 3rd September 2012, 11:20 PM   #27219
fas42 is offline fas42  Australia
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That's a nice marketing brief, but my question was "specify exactly in electrical terms what it has to do and not do." You need an electrical target for designing electrical equipment. If you're more interested in the marketing gloss, that's beyond my abilities.
I'll give you a nice one: a complete system, from source to speakers is recorded via top notch mic and ADC playing a variety of musical, highly testing excerpts at a realistic sound level. Then that system is subject to a variety of severe mains interference, RF interference stimula, in various combinations and strengths, vibration of some of the components, including cables, by controlled engineering devices, you get the idea. All variations are recorded, and then Diffmaker or whatever is run against the results. We'll be looking for variations of no more than 80dB below peak under all circumstances ...

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Old 3rd September 2012, 11:28 PM   #27220
SY is offline SY  United States
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Aeronautical and I were talking about preamp design, which is a simple matter (again, assuming evaluation with ears alone) once the electrical target is specified.

I'll leave the complex and speculative experiments covering other parts of the signal chain to others. I'll be interested in the results if they can show a correlation with ears-only listening tests.
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