I'm working on a project in which I want to be able to have some light effects based on the ambient music. I was thinking of sampling a mic and running an FFT, and set effects according to that.

Is that even viable to preform FFT on signal sampled from a mic (after amplification of course) for that purpose ? (quality wise) Should I even bother with this ? Or just have a line in input instead ?

I will be using this Electret mic. What kind of amplitude can I expect to get from it ? How can I model it in LTspice ?

My system is running from a 3.3v regulator which is fed from 12v. The ADC (inside an MCU) would have a 3.3v reference, I would need to bias the signal with VDD/2. The ADC is 12bit, Should i sacrifice the ADC resolution and have the signal swing less than VDD/2 (elimination the need for rail to rail op amp ?).

How do I choose an op-amp for this application ? I guess I'll need a low voltage offset op amp (how low ?). Should I power the opamp from the 12v supply ? Should I throw in another linear regulator to power the opamp ? Should I somehow split the supply ?

Thanks in advance, Mike.

  • 2
    \$\begingroup\$ You have actually asked several questions that are somewhat unrelated. You will probably get better answers if you split this up into separate, specific questions. \$\endgroup\$
    – Joe Hass
    May 21, 2014 at 15:20

1 Answer 1


Digital Signal Processors can do the FFT in real time. They have a particular architecture which means that certain instructions (MAC - multiply accumulate) can be done very quickly.

But then this turns in to an embedded software project too as well as the electronics design, if you're ok with that.

You can get development boards from companies such as Texas Instruments which contain a processor and break-out box arrangement for experimentation.


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