Another is here : Audio Spectrum Analyzer - Circuit Desgin Project | PDF | Electronic Filter | Electronic Circuits
It looks nice, 10 x 10 matrix (10 frequencies, every has 10 leds) , theory explained, whole circuit plus pcb ...
Another is here : Audio Spectrum Analyzer - Circuit Desgin Project | PDF | Electronic Filter | Electronic Circuits
It looks nice, 10 x 10 matrix (10 frequencies, every has 10 leds) , theory explained, whole circuit plus pcb ...