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Last night I built a circuit that allows me to obtain sound via a SEED Grove Sound Sensor and input it into my MKR Zero for frequency analysis.

It's as simple as this:

schematic

simulate this circuit – Schematic created using CircuitLab

You just talk or whistle into the mic and it outputs frequency values.

It works very well but it picks up ambient sound of course.

Sound Sensor Schematic

I examined the Sound Sensor schematic and noticed that it is a very nice amplifier circuit using an lm358. amplifier circuit

Now, I'm wondering, could I build that same circuit and replace the electret mic with one of these audio connectors and expect a similar functional experience when I connect an electric guitar?

audio connectors

If you need more details on those see product listing at https://amzn.to/2CkTO0g

Basically, I'm wondering if that amplifier circuit will work to increase the levels from the guitar input enough for the MKR Zero code to read it in the same way as the microphone is being amplified.

Or should I expect that the guitar input would be at a lower level and require more amplification?

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  • \$\begingroup\$ I have an adapter that will convert my guitar plug to 3.5mm, thanks. Is there a GE (Guitar Exchange) site? :D Also, I guess I'm wondering how the levels are different from electret mic to audio input? The Guitar people might not know. If you can offer a way to measure I can do that too. Maybe measure voltage across electret and compare to voltage across pins on audio input?? \$\endgroup\$ – raddevus Oct 16 '18 at 19:58
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    \$\begingroup\$ Mic level is a bit lower than instrument level out. Both are much lower than line level. But that schematic looks like nothing more than a 2 stage pre-amp with a bias voltage section for the mic. \$\endgroup\$ – Passerby Oct 16 '18 at 20:06
  • \$\begingroup\$ Thanks for the info. And that probably makes sense on the amp circuit, since I'm guessing it doesn't have to boost the signal too much. \$\endgroup\$ – raddevus Oct 16 '18 at 20:08
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    \$\begingroup\$ It has a total gain of around 100 (that's two stages of 10.) So, 40dB. That's a fair amount of gain for a microphone. Probably more than line level out. Using this together with a guitar signal would probably be (way) too much of a good thing. I would bet that the guitar level would be high enough for the MKR as is. \$\endgroup\$ – JRE Oct 16 '18 at 20:23
  • \$\begingroup\$ @JRE Thanks very much. I will try the guitar straight in and see what happens. If that works it will definitely simplify my circuit building. :) \$\endgroup\$ – raddevus Oct 17 '18 at 12:20

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