John Curl's Blowtorch preamplifier part II

[john curl]

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.

[john curl]

Be careful of mumetal, however, or even steel, as a shield.

[john curl]

Aluminum only, or non-magnetic stainless steel.

[morinix]

Originally Posted by Pano

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.

[Ken Newton]

Originally Posted by john curl

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.

[Joshua_G]

Originally Posted by john curl

Aluminum only, or non-magnetic stainless steel.

How about copper, or silver plated copper?

[bcarso]

Originally Posted by Joshua_G

How about copper, or silver plated copper?

Cu is great but difficult to machine and very expensive thus.

[aeronautical]

Originally Posted by john curl

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?

[fas42]

Originally Posted by SY

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 ...

Frank

[SY]

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.