Electrical Engineer side project help

Thread Starter

circuit28

Joined Apr 13, 2018
9
hello, im trying to replicate this project to get a better understanding on how circuits work:https://makezine.com/projects/audio-spectrum-analyzer/ The bandpass filters frequency ranges weren't stated so i tried to calculate them and I got some odd numbers, specifically for the first band pass filter. Can anyone tell me what I did wrong? Also what are the 22k and 390k resistors used for?
 

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Thread Starter

circuit28

Joined Apr 13, 2018
9
Ok i feel stupid, the 22k and 390k resistors are to calculate the gain of the circuit. Still need help trying to figure out what i did wrong in my calculations please
 

Jony130

Joined Feb 17, 2009
5,539
There is nothing wrong with you calculations. It is not your fault that someone else's chooses bad components values.
 

Thread Starter

circuit28

Joined Apr 13, 2018
9
ok so I decided to redesigned the band pass filters, since I want a total frequency range of 30-30khz I'm thinking of 30-3k, 3k-20k, and 20k-30k. What would be a good gain for the circuit? Also how would I connect all the bandpass filters to the display circuit? Am I right in thinking of connecting the three outputs of the bandpass filters together and making that the signal in of the display circuit?
 
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