[sdiy] some observations : audibility of phase distortion

[harrybissell]

My Hex Fuzz Guitar has all the outputs run through an allpass filter...
it is for vibrato generation.  I do not bypass the filter when the
vibrato
is stopped... I just stop modulating it.

I cannot hear any difference between  the original (pre filter) sound
and the
post filter sound... but by looking at the scope you cannot even
recognize
the same waveforms.

Phase insensitive (I say)

H^) harry

Czech Martin wrote:

> During the vacations I made some experiments.
> Unit pulses and a short drum sample were filtered
> with a discrete all pass filter. I checked that the amplitude
> of that filter was flat, but phase was very nonlinar.
> The nonlinearities where arround 100-400 Hz.
> I tried 2nd , 4th and 6th order.
>
> The signals were visibly distorted, but:
>
> I couldn't hear a difference, even if the original sample
> follows imediatly after the processed with less then
> 1s distance. Looping serveral times and using good headphones
> did not help.
>
> What is wrong with my experiment?
> I think that the time domain effect is still occlused (SP?),
> i.e. the filter response is too short  to be heard.
> That would mean higher order and / or higher filter "Q",
> i.e. poles closer to unit circle.
> E.g. if two pulses follow too close to each other you will
> hear only one, with perhaps some coloring. The ear has some
> time limitation.
>
> m.c.