need some assistant on the op-amp circuit attached in the thread.

[Techone]

@yaantey

I forgot that I tweek the gain of both op-amps for a better result but using a LM339. The LM358 is design for a dual power supply rail ( + - gnd ). The LM339 is design for a single power rail ( + gnd ), so that why the simulation give me a better result. But if you insisted to use the LM358, use two 9 V battery, connect them in series, take the plus for your positive rail, take the middle +/- <-- between batteries for your gnd, and the neg of the battery for the negative rail. But it will not be suitable for the analog pin. I recommend your order a LM339.

PS: I did a simulation for the band-pass filter. Need more tweeking and experiments. But I am close... 

[Techone]

@yaantey

Here a schematic I did using LTspiceIV.  The frequency responce is close to want you want. The simulator did not have LM358, so the 3 op-amps using a dual power supply, you can use a quad op-amp ( 4 inside ) - TL074 will work best. The last op-amp, you can use a LM741 or better <-- a single op-amp.

[Techone]

@yaantey

Here the frequency responce of the circuit. You can use your simulator to tested more and experiments.

That the best I can do so far...