Electronics > Projects, Designs, and Technical Stuff
world's most shielded cheapo USB sound card: 100g copper
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eliocor:
the frequency response of such USB sound cards is awfu: at 44kHz sampling rate, upper than 7.5รท10kHz is several dB down!
When you approach the Nyquist frequency there are LOTS of aliasing products....
Nothing changes trying to use a much higher sampling frequency as Theremino does: such USB sound card ALWAYS samples at 44kHz.
Several years ago I discussed this problem with the Teremino developers team (IIRC Livio?) and I received NO technical answers on why they used such high sampling rate if the frequency response and quality of the card was so abysmal!
ChristofferB:
Yeah as I've understood it, the MCA that the theremoni people did was more or less a side project. There is also the 'PRA' free soundcard MCA by a Marek Dolleiser that looks promising. I've seen a demo of that software, notebook mic input plugged directly into the tapped mid-amplifier stage of a handheld scintillation counter giving decent enough spectrums to identify isotopes.

https://www.gammaspectacular.com/blue/software-downloads/pra-spectrometry-software

The only reason I'm so hung up on the soundcard method is that I want to verify my detector setup actually works before I buy/make/program my own MCA.

The frequency response of the sound card is actually not that critical, since I have a shaping amplifier in front of it, making all incoming pulses very similar in peak shape / pulse lenght, and very close to gaussian.

Thanks for the insight, though!
 
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