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3 Channel Equalizer - Bandpass 4th order

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S!nn3r

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i would appreciate if anybody could help me with a circuit design for an Equalizer. i should realize the board for a connection with STM32F411 Discovery (it would be a second part of task).

It is an example for a study. Recently i received this project to realize, original text is in German but there are details:

3 Channel Equalizer:

Bandpass for frequencies 100Hz, 1kHz, 10 kHz
those frequencies should be gained trough potentiometer from +12dB to -12dB
Band-passes should be min 4th order
as an input source should be used BNC-socket
output signal to be transmitted to an existing AD channel
simulation in Multisim or Spice

Thanks for help
i guess that the way of circuit design is not as much complicated for someone who already has experience with this tasks
 

Tony Stewart

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Normally when high order than 2 with widely spaced center frequencies, would have both a bandpass and a skirt slope rejection specification or some standard filter characteristic, such as max flat amplitude, linear phase etc.

For audio I might suggest a parametric design if only 3 or use full,1/3 or half-octave BPF BRF using gyrator filters.
 

audioguru

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I have never needed and never used a mid-frequencies bandpass equalizer because my speakers have good frequency response. For some audio programs I have boosted or cut the bass and treble tone conrols a little.
 

S!nn3r

New Member
This circuit is to be realized, not something what i designed, it is the task.

here is 1 of solutions for 1 channel but i am not sure what and how should i regulate gain of +-12

and i have to do it for all 3 bands
 

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audioguru

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This circuit is to be realized, not something what i designed, it is the task.
Then it is a school assignment?
You show two Multiple Feedback Bandpass Filters in series. Why two of them??
This filter has a narrow frequencies peak then the slopes away from the peak are very gradual at only 6dB per octave which is not what you want.
 

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audioguru

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Your teacher probably wants the bandpass filters to be made with a 4th order Butterworth highpass filter then a 4th order Butterworth lowpass filter that will produce a flat bandpass without peaking.
 

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ronsimpson

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STM32F411
I am a little confused. I staid out of this because I thought this is a software project.
I see pictures of op-amp filters.
I think you have the "computer" to build all the filters in software.
Read in the audio in real time. Do the filters and gain adjust in math then send the data to a DAC.

Question: is the is a hardware or software project?
 
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