basic electronics question- 'filters'

[plexi12000]

some of the pcb's i've purchased use a capacitor and resistor at the input to prevent 'popping' when using the footswitch.

is that 'pairing' called  a filter? like a cap/restr. in a tone stack, for example?  thank you!

[Kipper4]

Most times on the input I've seen the anti pop resistor to ground Before the cap. So unlike a normal RC filter (tone filtering) which say for example a high pass filter (series cap followed by cap to Gnd)
Or low pass filter (series cap followed by resistor to Gnd) notice how in the signal path the second element (componant)of the filter is after the series element.
The anti pop resistor is before series cap.
The series cap at the input will shape the tone but not with the help of the anti pop resistor.
So I guess you could say the series cap has a filtering effect but in combination with the anti pop it does not form a filter.
Unless I'm very much mistaken.
By the way a quick and easy way for me to remember which filter is which .
Series resistor/Cap to ground (cap at bottom) low pass filter
Series cap/resistor to ground (resistor at bottom) high pass filter

[R.G.]

some of the pcb's i've purchased use a capacitor and resistor at the input to prevent 'popping' when using the footswitch.

is that 'pairing' called  a filter? like a cap/restr. in a tone stack, for example?  thank you!

Early on in an EE education, the concept of the difference between time domain and frequency domain responses comes up.  "Time domain" is what the signal voltage or current is doing at one instant in time, and how this changes with time. It's best thought of as something like how the dot on an oscilloscope display wobbles up and down with signal voltage as the dot is swept left to right by the internal timing circuits. "Frequency domain", is tied into the idea of what sine waves make up the signal you're seeing, as computed over some long period of time, not an instant. For instance, if you listen to a sine wave, you hear one frequency. If you add another frequency to it, you hear both. The Fourier Transform makes a frequency spectrum of those two signals as two spikes at two different frequencies.

Yes, yes, I'm coming to the point.   

Filters are frequency domain devices. They let through some frequencies essentially untouched, and attenuate others, over any period of time. Every R-C network is a filter of some kind.

But every R-C network also has a time response. This is best thought of (and how digital filtering uses the concept!) as the response of the R-C network to a single, instantaneous "blip" of signal - an "impulse". The impulse response of the RC network and the frequency response of the same network are unique to each other - if you know one, you know the other.

With all that behind us, the RC network at the input and output of pedals is not used as a filter, nor used for its impulse/time response. It's a DC load resistor. It *prevents" impulses and steps. It does this by being a much lower resistance than the leakage through the input capacitor, so that when the capacitor is open-circuited by a footswitch, the resistor still holds the cap's now-free end at ground, so when the cap is reconnected, there is no transient to be filtered.

So while it IS a filter, but it's not used as a filter.

How's that for complicated? 

[bool]

In frequency domain, it is used to filter out the 0Hz component (the DC offset).

[antonis]

high pass filter (series cap followed by cap to Gnd)
low pass filter (series cap followed by resistor to Gnd)

Rich....!!!

(I think that your keyboard makes an excellent confuse-pass filter..)

[Kipper4]

Excuse my keyboard.
High pass filter series cap and resistor to gnd
Low pass filter series resistor and cap to ground