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Sallen Key Low Pass Filter, bandpass filter

bertus

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Hello,

Did you also change R20 and R21?
What is the complete schematic now?

Bertus
 

Maglatron

Jul 12, 2023
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this shows the place where I put the, out of the filters
1702500173502.png
this shows the ammended resistors
1702500109138.png
 

Maglatron

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complete circuits yes changed the resistor R20 and R21!!
7000Hz1702500355670.png
45Hz1702500310524.png
 

bertus

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Hello,

I see that C12 is 0,1 uF. Change that to 10 uF.
This will give the 45 Hz a higher throughput.

Bertus
 

Maglatron

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Hello,

I see that C12 is 0,1 uF. Change that to 10 uF.
This will give the 45 Hz a higher throughput.

Bertus
What will higher throughput do and how does it help with the 7000Hz filter? thanks, it hasn't seemed to have done anything noticable!
 

bertus

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Hello,

The impedance of the 0.1 uF capacitor is to high for the 45 Hz.
At 7000 Hz the impedance is low enough to pass the signal.

Read the AC section of this wiki page:

Bertus
 

Maglatron

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nope not yet still tops out I hope you have not exhausted your ideas:) thanks again for helping this is the last part if we get this running for the lowest frequency and the highest frequency then the middle frequencies should work.1702501313757.png
 

Maglatron

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did you run the sim I uploaded the sound file in the form of .txt and the .asc file for the 7000Hz
 

Attachments

  • 7000Hz - Copy.txt
    1.7 MB · Views: 1
  • 7000Hz.asc
    16.6 KB · Views: 0

bertus

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Hello,

Is the 45 Hz now also clipping?
The gain should be highr at 45 Hz.

Bertus
 

Maglatron

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No but the highest peak now reaches 9 volt instead of the prefered 8.4 so it has adjusted it slightly, I think we're getting somewhere!
I don't know if this helps but I want to remind you that the circuit worked as desired when R13 was 4.7k and R23 was set to 1k but thats not acceptable because I want the one pre-amp and amp for all of the filters!
 
Last edited:

Maglatron

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It's not even dipping look at the time on the 45Hz and when the peaks and troughs there are no troughs on the 7000Hz analysis1702504304446.png
 

bertus

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Hello,

I did run the 7000 Hz with changed parameters:


Plot 7000 Hz.png

Sorry for the firefox overlay.

Bertus
 

Maglatron

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Sorry my mistake the two audio files are different for the 45Hz and 7000Hz, they are not related in any way!
 

bertus

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Hello,

The 7000 Hz file seems to be an older version, I needed to change the following:

C12 = 10 uF
R23 = 15 K
R13 = 27 K
C15 = 10 uF
R20 = 100 K
R21 = 500 K
C17 = 10 uF

Bertus
 

Maglatron

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simulating this looks good! so now will this pre-amp and amp be good for all the frequency filter I will simulate one in the middle of 45Hz and 7000Hz and see what it's saying thank you very muchly
 

Maglatron

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so it ran and it's really good for the 7000Hz it reaches 8.4v on the envelope detector But for the 45Hz and the 8th filter on the list (474Hz) they both only reach to a maximum of nearly 6.1 volts but at least now they are all showing on the chart now!!! definatly getting somewhere!!1702547298282.png
 

Maglatron

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474Hz again the txt file is the .wav
 

Attachments

  • 474Hz.asc
    16.6 KB · Views: 1
  • 474Hz - Copy.txt
    1,023.7 KB · Views: 0
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