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Simple RC bandpass with LEDs

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StickyPants

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I have searched high and low trying to find a way to have (for example) 3 LEDs, that light up according to different frequency ranges.

The intended result would be a box with audio input, LEDs that react to different ranges, and pots to select the ranges.

So basically you could have 1 LED for bass, 1 for mid, and 1 for treble.

The frequency range for each LED is selected with a pot/knob.
Perhaps there should be 2 pots for each LED, the 1st pot sets the min and the 2nd pot sets the max frequency (each LED has it's own bandpass)

There is a lot of information about RC filters out there but none seem to go in this direction. Any better ways to implement? I don't know where to start. I just want to get ONE LED going, even without a pot. Any help is appreciated.
 
What you describes sounds like an audio analyzer. I think AudioGuru designed one and posted it awhile back, perhaps he might be nice enough to share it again with you.
 
I never made and never posted an audio spectrum analyser. They use 10 frequency bands or more.
A simple 3-band one is called a color organ and there are many circuits on the web, look in Google. They do not need and do not use variable frequencies.

The low frequency filter is an active second-order Butterworth lowpass filter.
The middle frequency filter is a multiple-feedback bandpass active filter.
The high frequency is an active second-order Butterworth highpass filter.

Each filter feeds a rectifier peak detector circuit.
 
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