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  1. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Bertus
  2. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Any 16 Volts electrolitic or tantal capacitors will do. In the amplifier there is not much voltage on the capacitors. For the powersupply of 12 Volts and the ref voltage, the 16 volts capacitors will do. Bertus
  3. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, I found the failure. In the 7000 Hz filter R12 was 43 Ohms in stead of 43K. Now R13 can be adjusted to 820K and I get a peak of 7.4 Volts for the 7000 Hz filter: The green line is the output of the preamp. I have also attached the wav file I used. Bertus
  4. bertus

    Sallen Key Low Pass Filter, bandpass filter

    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
  5. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, I did run the 7000 Hz with changed parameters: Sorry for the firefox overlay. Bertus
  6. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Is the 45 Hz now also clipping? The gain should be highr at 45 Hz. Bertus
  7. bertus

    Sallen Key Low Pass Filter, bandpass filter

    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: https://en.wikipedia.org/wiki/Capacitor Bertus
  8. bertus

    Sallen Key Low Pass Filter, bandpass filter

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

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Did you also change R20 and R21? What is the complete schematic now? Bertus
  10. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Now you have R13 at 4K7 and R23 at 165K. Change that to R13 at 27K and R23 to 1Meg and see what happens with 45 Hz and 7000 Hz. With those values C14 will have a factor of 6 less influence on the frequency dependend gain. Bertus
  11. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Yes, that way you can see the effect on low and high frequency. Bertus
  12. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Yes, the values of C15 and C17 need to be the same to have the same effect on the frequency. I see an other solution, Raise R20 to 100K and R21 to 500K and see the effect. The capacitors would have less prone effect on the frequency in that case. Bertus
  13. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Do you still use the attenuator at the source? The gain at higher frequencies can be caused by in series with R13, the 22 uF capacitor C14. Also C15 and C17 of the amplifier are frequency dependend. Try to adjust the 45 Hz version for max output by raising the value of C15 and C17. Also...
  14. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, A lot of information on LTspice can be found in the LTWIKI: https://ltwiki.org/index.php?title=Main_Page Bertus
  15. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, The sim will need a lot of resources to run. Larger memory will already make a difference. My home computer has 32 GB of internal memory. Bertus
  16. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, Why do you need a 20 Watt load? As for the filters, you only need one amplifier: Bertus
  17. bertus

    Coffee pot component.

    Hello, The thermal fuse is a safety device. Removing it might cause fire. When the insurance finds out that the fire started with the coffie pot without the thermal fuse in it, you will not get payed. Bertus
  18. bertus

    Balancing act RLC circuit

    Hello, Read the attached PDF about powersupply circuits. From page 24 and on there are formulas for the things you do. Bertus
  19. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, As for the schottky diode, you could try a BAT43. That is one with wires and not SMD as many others. Bertus
  20. bertus

    Sallen Key Low Pass Filter, bandpass filter

    Hello, The value of 165K may be ok for the simulation. You will have to adjust the value again in the live situation with the real mic. Bertus
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