Electronics > Open Source Hardware

Simple open-source condenser studio microphone with a modern twist

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Spirit532:
Everything is on github, not going to duplicate the description here, just going to say that this was my first time using a hex inverter as a charge pump, maybe there's people here who aren't aware that this is a cool trick to get high voltages with low part count, price, and noise.

https://github.com/Spirit532/studio_mic

Critiques welcome, I suppose.

JohanH:
Interesting, thanks for sharing. I've thought of getting a (better) mic, but it would be a great idea to build one instead.

Just a comment about ceramic capacitors. Any class 2 capacitor will have loss of capacitance at higher voltages. It doesn't help with higher voltage rating. Larger package and higher temp dielectric helps somewhat (so X7R/X8R in larger case). But class 1 capacitors are best, C0G(NP0). They will have virtually no loss of capacitance at higher voltages. They are more expensive, though, and isn't available in higher capacitance values and all package sizes.

Spirit532:

--- Quote from: JohanH on March 18, 2023, 01:38:56 pm ---Any class 2 capacitor will have loss of capacitance at higher voltages. It doesn't help with higher voltage rating.

--- End quote ---

It's good that you pointed that out!
I'm aware of this, but the note I made about capacitors is more to do just with the voltage rating. 100V caps will typically be X7R(at least the ones I've looked at briefly), which have good enough capacitance for what's happening in the circuit. Derating by even 70% is acceptable, but it's the unexpected behavior(failure, really) if you go too close to the rated voltage that's the biggest issue.
Since it's aimed at less experienced people and perhaps non-EEs, I just chose to generalize, if a bit wrong.

TimFox:
The 1 nF and 10 nF capacitors should be available in NP0/C0G.
100 nF C0G capacitors are rather large.

Spirit532:

--- Quote from: TimFox on March 18, 2023, 01:49:22 pm ---The 1 nF and 10 nF capacitors should be available in NP0/C0G.
100 nF C0G capacitors are rather large.

--- End quote ---

Those are ones that really matter the least, so going for price is more important.

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