RL Low Pass Filter Calculator

[AltAudio]

Hello,

Any suggested sites that will allow me to tinker with various RL passive low pass filter configurations? I'm trying to filter out 18K and above from audio signal and thought to try passive route first.

Many thanks........Mickey

 

[JimB]

Why the L ?

RC filters are much cheaper to construct.

Inductors for audio frequencies tend to be expensive.

JimB

 

[AltAudio]

Well every iteration I've tried with RC seem to attenuate the entire signal. I've had good luck with RL configuration with 150Hz low pass and thought to build upon this experience.

 

[crutschow]

For a given roll-off frequency, there's no difference between an RL and and RC filter. A simple 1-pole, RC LP filter with a -3dB point of 149Hz can be constructed with a 10.7kΩ resistor in series with a 0.1µF capacitor to ground, for example.

 

[AltAudio]

Ok then, so can you recommend a utility/site that will calculate?

 

[crutschow]

Ok then, so can you recommend a utility/site that will calculate?

Google turned up many, including this.

 

[MrAl]

Hello,

You need to tell us what kind of power level you are working with. For an inter-stage audio section you can get away with a lot more than if you have to drive a 8 ohm speaker with this at 100 watts.

Using an inductor rather than a capacitor can cause less attenuation if you can work that inductance against the output impedance. An inductor in series with the output may work ok, and an inductor in theory has no loss. An inductor with low series resistance may work well for your app, but we have to know more about what you are using to drive this with and what you are driving with this. Low power inductors are not expensive and it does seem that you are working at a decently high frequency so that should keep cost down, if in fact you are working at low power that is.