Have I made a Bandpass filter with this dual R-C filter?

[kimelopidaer]

The following picture i based on a diagram of the muff tone stack over at AMZ effects.
Regarding band pass filters - For example let's say i wanted to pass only frequencies from 80 - 200 hz.
I chose component values for the high (>80hz) and low (<200hz) pass filters that combine to create this filter.
I used AMZ's R-C filter calc.

I would appreciate any comments regarding this method; I've also seen the high and low pass filters connected in series.
What if I just want a static value from the filter and I omit the voltage divider at the output?



ThankYou,
K

[_dB]

I believe the POT allows you to blend between the low passed and the high passed signals.  I guess at the mid point you'd get more or less a bandpass filter?

For static values the series configuration this is probably what you want: http://www.electronics-tutorials.ws/filter/filter_4.html  (fewer parts)

[ubersam]

download the duncan tone stack calculator and plug your values in to see how the filter behaves http://www.duncanamps.com/tsc/

check this page out for some examples of passive rc bandpass circuits: http://www.electronics-tutorials.ws/filter/filter_4.html

[PRR]

R1 C1 passes DC to 199Hz.

R2 C2 passes 80Hz to infinity.

So it passes everything.

In general, a parallel-path network like this can ony be all-pass or notch.

For simple bandpass, put the networks one after the other. First cut off bass, say at 400Hz. Then cut-off treble, say at 2KHz. Result is 400Hz-2KHz bandpass. Not a *sharp* band-pass such as fancy filter textbooks get into, but musically useful anyway.

[merlinb]

Regarding band pass filters - For example let's say i wanted to pass only frequencies from 80 - 200 hz.
I chose component values for the high (>80hz) and low (<200hz) pass filters that combine to create this filter.

Yes you make it bandpass, but it is pretty pathetic bandpass. You would do it the opposite way to the way you describe- HP filter set at 80Hz, LP filter set at 200Hz. Try out Duncan's TSC:
http://www.duncanamps.com/tsc/

[earthtonesaudio]

No, a LPF and HPF in parallel (as in the drawing) makes a notch filter.

A LPF and HPF in series makes a bandpass filter.

[merlinb]

No, a LPF and HPF in parallel (as in the drawing) makes a notch filter.

[CynicalMan]

I'd call that a peak filter, not a bandpass. Bandpasses usually reduce frequencies beyond the pass band towards 0. That one just increases the centre frequency towards 1 while the other frequencies are attenuated by a set amount. Still, I'm not sure that wouldn't fall into the strict definition of bandpass.

[kimelopidaer]

I see it now, thank you everyone for the replies -
The arrangement as I had it will attenuate frequencies above 200hz with the Low pass,
but then the High pass arrangement will allow all those frequencies to pass through anyway -

Putting the filters in series will let me do what I want.

Cheers for the learning,
K

[earthtonesaudio]

Thank you for the correction Merlin.  I did not look close enough at the values. 
The parallel arrangement is what's used in the Big Muff and its many derivatives, where the values are often chosen to produce a notch response.  Upon closer look the parallel arrangement can be tweaked to produce a notch, or a mostly-flat response, or a mid bump.