Mastodawn

What have I been #mayke-ing lately? The white box on the left is a breakout from Baofeng/Kenwood headsets to separate standard ear/mic/push-to-talk leads; the PCB it's plugged into on the right is a microphone pre-amp that powers a microphone and brings the signal up to line levels! And both actually work!

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Alaric Snell-Pym May 10, 2023

Two stages of low noise transistor class-A amplification, then once it's up to levels where noise isn't a problem, an op-amp for final gain tweaking and a nice low impedance output drive. Slightly overkill, but I wanted to put learning to practice, so made it a belt-and-braces design.

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Alaric Snell-Pym May 14, 2023

So, the standard Baxandall tone control circuit - the "Bass" and "Treble" knobs on every hifi - turns out to do next to nothing to human voice in my microphone pre-amp, probably because voice is in the 300-3000Hz range while the tone control is built for a much broader range found in music, which means I'm gonna need to design my own circuit rather than going off-the-shelf. Not a problem, just means I can't get to the much more fun VU meter stage yet!

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Alaric Snell-Pym May 14, 2023

I'm resisting the temptation to just drop in a DSP as it would be a big diversion, although getting the signal into the digital domain for processing would be much more in my comfort zone. But the modular design of this thing means I could swap it out for a DSP in future and implement fine EQ, echo cancellation, compresion, dynamic noise elimination, Dalek voice effect, etc...