I need to make an active low pass filter with variable cutoff up between 0 and 4khz. I don't know anything about electronics but can follow a schematic, can anyone help?
I need to make an active low pass filter with variable cutoff up between 0 and 4khz.
It's incredibly simple given those parameters. Do you have a breadboard and some through hole components to make it with? You won't make one that can accept mains (wall outlet) voltage from scratch and not be a huge fire hazard.
It’s for a synthesizer
Frick you, buy one that sounds good.
If it's a school program it's fine, otherwise kill your self.
idk
with unity gain
what's the purpose of R3?
>what's the purpose of R3?
Makes the parallel combination of R1||R3 logarithmic.
Can you explain? Can't you just use a log pot?
And what makes the parallel connection logarithmic? isn't 1/R = 1/R1 +1/R3 the integral of ln(R).
Also what if R1 is turned down to 0, wouldn't it short R3? So only R2 C1 C2 are left. But your equation for fc has (R1+R3), and if R1 is zero it will become R3*R2*C1*C2 which seems wrong since like I said if R1=0 R3 is zero as well?
it should be in series and not parallel
it was to set a minimum resistance across r1 to set max fc=4000
im more sober now
Since some of you seem to know what you're talking about ...
I was looking for baseline information on crossovers, and ran into this old website:
https://www.calsci.com/audio/X-Overs.html
It seems like a great starting place for a novice, but since I don't know what I don't know, I don't want to be misled down the wrong path ... does it at least seem like accurate info on this page?
Look up a 1st order butterworth filter. It's super easy.
They have more complicated ones, but this might work well enough for you.
chatgpt
Certainly, I can help you with that! An active low-pass filter is a circuit that allows low-frequency signals to pass through while attenuating higher-frequency signals. To create an active low-pass filter with a variable cutoff frequency between 0 and 4 kHz, you can use an operational amplifier (op-amp) based circuit. One common type of active low-pass filter is the "Sallen-Key" topology.
Here's a simple schematic and explanation of how to build a variable cutoff frequency active low-pass filter:
**Components Needed:**
- Operational amplifier (op-amp)
- Resistors
- Capacitors
- Potentiometer (variable resistor)
**Schematic:**
```
R1 R2
+---///----+---///----+
| | |
| C |
| | |
Vin --+----|+|------+-----+ |
| |
| | |
|R| |
| | |
| |
GND |
|
Vout
|
GND
```
**Circuit Explanation:**
- Vin: Input signal
- Vout: Output signal
- R1: Feedback resistor
- R2: Input resistor
- C: Capacitor
- GND: Ground
The cutoff frequency of the low-pass filter is determined by the values of R and C in the circuit. To make the cutoff frequency adjustable, you'll replace one of these components with a potentiometer (variable resistor) so that you can change its resistance value.
1/2 part
**Steps:**
1. Choose a value for R1 and R2. You can start with equal values (e.g., 10k ohms).
2. Choose a capacitor value (C) that will allow frequencies up to 4 kHz to pass through while attenuating higher frequencies. You can calculate the capacitance using the formula C = 1 / (2 * π * R * f), where f is the desired cutoff frequency (in Hz).
3. Replace one of the resistors (let's say R2) with a potentiometer. This potentiometer will allow you to vary the resistance and, consequently, the cutoff frequency.
4. Connect the components according to the schematic.
5. Power the op-amp with a suitable voltage supply (e.g., +Vcc and GND).