Avoiding the output of an active LP or HP filter being phase shifted

Thread Starter

dyn_o

Joined May 29, 2017
35
Hi,

I’m making a little synth with an oscillator and 2 active filters, LP and HP. Because of the non linear phase response of the filters, the output signal doesn’t have the same phase as the input signal from the osc, but I don’t want this lag. Is there a way to avoid it (without digital filtering) ? I don’t think so but maybe you guys know.
 

crutschow

Joined Mar 14, 2008
23,377
In general no.
Phase shift is an unavoidable result of filtering a signal, even using a digital filter.
But a properly designed BP filter should have zero phase-shift at the center frequency.
 

danadak

Joined Mar 10, 2018
3,578
FIR filters are linear phase.

https://dsp.stackexchange.com/questions/31726/why-is-a-linear-phase-important

http://repforums.prosoundweb.com/index.php?topic=34739.0

Are you seeking linear phase with no latency/time delay ? Or faithful
reproduction of input phase at the output, delayed in time ?

https://www.uaudio.com/blog/allpass-filters/

Linear phase just means response of filter to frequency exhibits a linear phase
plot.

https://en.wikipedia.org/wiki/Linear_phase

https://dsp.stackexchange.com/questions/206/what-is-the-difference-between-phase-delay-and-group-delay



Rergards, Dana.
 

crutschow

Joined Mar 14, 2008
23,377
I wanted to have the exact same output signal that the input signal, because I tought the sound would not be the same at the input and the ouptut.
The ear is quite insensitive to phase-shift in an audio signal.
And if you want the input and output to sound the same, why the filter?
 

Thread Starter

dyn_o

Joined May 29, 2017
35
The ear is quite insensitive to phase-shift in an audio signal.
And if you want the input and output to sound the same, why the filter?
Mmhh, I didn't really mean sound the same, I know the filter alters the sound, but I wanted to keep a kind of control over the phas. Having the phase to shift without I decide it is like an out of my control thing and I don't like that.
 
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