Nixie Tube Music Visualizer

Step 3 Design: Filter

Each audio channel splits out into 7 different bandpass filters. The filters are centered on 60Hz, 150Hz, 400Hz, 1kHz, 2.5kHz, 6kHz, and 15kHz. Each filter is a Fliege band-pass filter, which has a relatively low count of components, and works well from a single supply (0V and 12V, as opposed to +/-6V). Each Fliege filter uses two op-amps, so another cheap dual op-amp can be used.

The following chart gives the values of the resistors and capacitors for each bandwidth (R4 and R5 are both 10kohms). If you are calculating your own bandwidths, I used a Q value of approximately 5 (none of them are exactly 5 because of the limitations of standard resistor and capacitor values).

Comments

[fade400]

Does the value of Cin matter ?

[Senator Penguin]

The image annotations are a bit buggy, it should indicate that Cin isn't needed in this design, I didn't include it in the final schematic or board.