Audio High Pass Filter (4th order)

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Ah, that makes sense. I would expect 120Hz to be significant as well. Really, I would expect 120 to be more dominant.

I'd do some research on the transducer to see what your options are.
 

Somehow the word Photo got changed by Gary into Phono.
I was thinking of the humming sound in a video camera. Simply tell the camera man to stop humming.

Maybe sound is transmitted using light or Infrared and light bulbs are producing 60Hz and its harmonics as hum interference. I think a light bulb would produce 120Hz as a fundamental frequency wouldn't it? If it has a half-wave rectifier then it would be 60Hz.
 

Phono, photo, No worries, I just think that a HPF will likely work better than a notch because of the expected noise source. Perhaps I will need a 120Hz notch filter?

I will build it and test it and then should have more facts.

Thanks
 

Jester said:
Phono, photo, No worries, I just think that a HPF will likely work better than a notch because of the expected noise source. Perhaps I will need a 120Hz notch filter?

I will build it and test it and then should have more facts.

Thanks
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Possibly 120hz.
Or Possibly both a 60 and 120hz filters.

Notch filters can be set to a Very Narrow Bandwith, so less loss of data.

Also HP Filters Require a Better Quality Op-Amp, or you will Lose Higher Frequencies.
 

chemelec said:
Also HP Filters Require a Better Quality Op-Amp, or you will Lose Higher Frequencies.
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There are no high frequencies. "The pass band is specified as 180Hz to 2400Hz". Maybe an LM324 or LM358 will have a little trouble.
 
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Also HP Filters Require a Better Quality Op-Amp, or you will Lose Higher Frequencies.
Click to expand...
There's nothing specific about high-pass filters in this regard. Above the cut-off frequency, the shown Sallen-Key active filter is just working a +1 buffer, so the comment applies to a simple amplifier as well. An active filter needs however sufficient loop gain reserve around the cut-off frequency to implement the designed filter characteristic accurately.
 
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