Notch/Bandbass filter curves differ?

A band reject filter can be created with a parametric EQ, but can only have a "notch" of -12dB which is probably not the same as blocking.
 
A band reject filter doesn't fit the parameters since it is defined by two frequencies rather than f0, Q, etc. To make a band reject filter put a highpass and lowpass in parallel.
 
mmcm4 said:
A bandpass or notch filter is a high-pass and a low-pass combined together in series. The difference between the two is determined by where the -3dB cutoff frequencies are for the high and low pass filters.
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In series will work too depending on design. A graphic EQ does not run each band in series with the next stage/band, they are all in parallel and then summed up. Many amp tone circuits are parallel as well and summed in the next amp stage.
 
bobby_g said:
In series will work too depending on design. A graphic EQ does not run each band in series with the next stage/band, they are all in parallel and then summed up. Many amp tone circuits are parallel as well and summed in the next amp stage.
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The bands are in parallel in a graphic EQ, but the components of the bandpass filters are in series (ex. lowpass filter connected to a highpass filter).
 
No, a graphic EQ is a series connection of peaking filters. Peaking filters are not made up of lower-order highpass or lowpass filters. They are (typically) second-order filters with the poles and zeros moving in opposite directions on the root locus as you move the slider.
 
FractalAudio said:
No, a graphic EQ is a series connection of peaking filters. Peaking filters are not made up of lower-order highpass or lowpass filters. They are (typically) second-order filters with the poles and zeros moving in opposite directions on the root locus as you move the slider.
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I am smart enough to understand this. ;) :?
 
Actually old analog graphic EQs are not usually implemented as a cascade of second order peaking filters but as a single 2xNth order peaking filter. This is typically implemented by putting N biquads in the feedback path of a "master" op-amp.

It's too complicated to discuss here but it's equivalent to a series cascade of second-order-sections.
 
FractalAudio said:
Actually old analog graphic EQs are not usually implemented as a cascade of second order peaking filters but as a single 2xNth order peaking filter. This is typically implemented by putting N biquads in the feedback path of a "master" op-amp.

It's too complicated to discuss here but it's equivalent to a series cascade of second-order-sections.
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This was what I meant by in parallel: there's one stage but each filter section operates in parallel of the signal (at least this is how I interpret the schematic) Thanks :)
 
FractalAudio said:
Actually old analog graphic EQs are not usually implemented as a cascade of second order peaking filters but as a single 2xNth order peaking filter. This is typically implemented by putting N biquads in the feedback path of a "master" op-amp.

It's too complicated to discuss here but it's equivalent to a series cascade of second-order-sections.
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ok ok now you're just showing off and/or making up words :p :D!!!
 
bobby_g said:
This I believe:
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Ah, yes!

Anyway, I guess the question is more academic in nature (why don't these curves look the same), than practical (I'm trying to achieve a certain sound, and I can't) - because the suggestion "To make a band reject filter put a highpass and lowpass in parallel" allows this type of curve.
 
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