Low pass filter diy


2011-02-12 11:52 am
Hi Guys

I’m looking to construct a low pass filter. Having done some research I can see it would consist of a resistor, in series and a capacitor in parallel.

Would it be possible to change the order that is parallel the capacitor first and then add the series resister. I was actually looking to use the input impedance of the amplifier thereby only using a parallel capacitor.

Would this arrangement achieve the same result.

It’s quite clear from the research that Ive done for a high pass filter that the capacitor is in series and the resistor (amplifier impedance is in parallel) and that works ok.

Many thanks
No, that's problematical as it presents a capacitive load to whatever drives it, which can cause instability.

Amp input impedances are sometimes not constant and well defined, and many amps assume a low driving impedance - so its often problematic to use a passive filter on the input to an amp, a buffered active filter stage is preferred.

Passive filters always interact with the source and load impedances.