Preparing guitar signal for ADC input - Arduino Due

[merlinb]

You appear to have drawn Rb6 as 1k. It should be 1M or something similarly large.

[PRR]

> 47k + (1M+100k || 200M)

I don't see how "100K" gets in there.

There's two 100K, both to AC ground, so that would be 50K.

But bypassed with C3. It's under 1K at the bottom of the audio band, less at higher freq. In a clump of 47K and 1Meg resistors, I'd call <<1K "zero". In fact the ideal value of C3 is "zero AC impedance" so that power supply crap is shorted-out. <<1K is again zero-enough for practical purpose.

Oh... You had an earlier plan with 2:1 attenuation then 1:11 of gain. If that actually worked, when you fix the input network for 1:0.95 attenuation you want to change the gain to 1:5.5, not 1:11. In fact I suspect even 1:5 overall gain is excessive for some guitars/players into a 3V ADC. Half-Volt peak from a guitar is not unknown, so gain of 3 may clip the ADC input.

[R.G.]

I'd still be tempted to put a diode clipper in, either two silicons for +/- 1.4V or two selected 1.6V LEDs. The clipping will be less harsh than letting some samples bang against the input limits.

[CatsLoveJazz]

Thanks, that makes sense, I wasn't thinking bout the fact the signal was ac. I was playing around with the gain values in my simulation but I would expect to be going for a gain of 5 or less in the final circuit.

Cheers guys, you have really been so helpful at every step of the way!