Nice one knob filter...clicking issue

#1

After that thread here about full bandwith filters and especially after @SmashedTransistors solution :

... I built this simple but nice "one knob filter" which can be found in many stuff like Elektron Cycles / Samples or TE Op-Z : sweep from LP (full counter clockwise) to HP. Great.

BUT i have an issue in my design : there's an ugly "click" when switching from LP to HP. Dunno how to fix it.

Strangely, you can't hear it on a noise source. But with lower frequencies (ie a kick) it's noticeable everytime it switches from 0 (aka no filter) to >0 (start HP filter)

I'm using a mux for switching filter, which is very basic. Tried with xfade resulting in same issue.

Any idea welcome.

click.jpg1229x455 90.2 KB
dualFilterOneKnob_click.axp (13.2 KB)

#2

Hi! I don't quite understand what you want to achieve but the problem is that you use a mux object to switch HP to LP. In this case the waveform changes abruptly and a click is inevitable ... nothing changes if you put an xfade object because you control it with a discrete value (yellow cable). You should put an xfade object controlled by a blue dial, maybe with an lp after it (the dial)

#3

Yeah, xfade should do it, and yeah, the yellow signal would be too abrupt (yellow on/off into blue input is like a dial going immediately from 0 to maximum instantly).

Try putting something inbetween to slow down the change. Maybe:

20210408_144531.jpg1511x2015 1.5 MB

#4

There are different approaches to this in this thread.

#5

Thx. I had tried controlling the xfade through a LP before, it wasn't bringing much difference. Now if i put it slower, it's better.... but not perfect.
Using smooth works somehow on the opposite : you hear less click when going from 0 - <0, but you hear it when going from >0 - <0 ....

#6

Perhaps the highpass filter is coming out inverted. You wouldn't hear this phase difference while being in either lowpass or highpass, but the wave would invert when switching between the two modes when crossing 0, causing a sudden click.

#7

Hi! I don't hear any click in a patch like this LP_HP_FADE_PROVA.axp (4.4 KB)
And clicking the button you can see that the hp and lp out are perfectly in phase

#8

Found it. The problem was coming from my divided pot, switching too abruptly. Just added another smooth before attacking frequency input.
Thx !