HI Kennjava:
Thanks for the lead towards your document archive and the hopeful suggestions. I studied the pictures, diagram and docs. It's an interesting design. And, yes, I think we could utilize the 5 vdc power source from the USB rather than the battery. I redrew it with your electret suggestion and components that are currently online at Mouser. I didn¡¯t think that the functionality for the low pass and hi pass (I¡¯m presuming they are that) were needed. I¡¯m unsure if that delete breaks the circuit? maybe?
Being new here, I'm not certain if image files are uploaded with emails but I¡¯ll attach what I did. I would still lean toward using the Alice board if that¡¯s feasible but if not, perhaps I can get one of my electrical eng friends to critique the circuit changes I made to your battery-box design.
D
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On Feb 21, 2024, at 9:37 AM, kennjava <
ken@...> wrote:
On Tue, Feb 20, 2024 at 07:10 PM, David Lau wrote:
Where would I find a reliable diagram/instructions for [a battery box]?
I built a battery box like, um 22+ years ago, that served me for almost 20 years, and
parked the details in the files section of this site.You'll find schematic, notes and pictures there.
A few caveats on this design:
- I used tantalum capacitors for the larger values; they worked and are small, but to do again I would use electrolytic caps instead.
- It's kind of small and cramped, and it was hard to fit everything in there. A bigger enclosure is recommended.
- I selected 5.6k as the drain resistor to the 9v battery. It worked with the little omni electret capsules i've used. But you should probably make bench tests with your chosen electret to ensure that the voltage @ current at the capsule are within the maker's specs.
It gave me great service, but about 2 years ago that box started going intermittent, most likely due to the tiny switches. At that time i made a new battery box, this time with bigger switches, in a slightly bigger aluminum project box. But I've misplaced my notes on the new box [blush] so i can't recall what circuit changes I made. If/when I find them, I will update the notes on file here.
You also have the option of grabbing 5v from the USB connection.
Last suggestions: save yourself the hassle of working with a bare electret capsule and a separate FET, and select a capsule that has the FET impedance converter already included - examples: JLI-2590A, TSB-140A, PUI AUM-5241L-HD. For your application (desktop mic with basic USB audio adaptor) you will get very good results with one of these, without needing to jump through all the hoops of separate FET/opamp.
There are simpler preamp circuits than the "DIY-Perks" THAT opamp with its +/-15v requirements, that would run from the same 9v battery, or even from (USB) 5v. I don't have one to recommend, but others might.
Good luck!
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