[PD] What is that 4khz whine?

[cyrille henry]

hello,

Le 15/06/2016 07:46, William Huston a écrit :
> Simple square wave patch into a [vcf~] and a [bp~].
> Pass though 6-stage [lop~ 8000] to try to eliminate
> harmonics > nyquist (22.5khz).
> (attached).

This is not a good way to generate an aliased free waveform since all foldover frequency under 8KHz will not be removed.
you should try using a real band limited square oscilator.



>
> Set the Q to about 3.
> Now keep the frequency of the oscillator and the filter cutoff freq
> below 100 hz.
>
> Try [bp~] then try [vcf~].
>
> No matter what the setting of either (as long as they are both below 100 hz),
> I get I get a strong artifact at 4k, another at 12k, another at 17k.

i can see lot's of crap using your patch, but very few when using a good band limited oscilator.

>
> This has been bugging me for months.
> I can't figure it out.
>
> I thought it was super-Nyquist foldover,
> but the [lop~] didn't eliminate it,
> and it does not seem dependent on the frequency of the oscillator.
>
> Any ideas?

what did you use to record the sound?

cheers
c

>
> Sample rate=44100 hz. Delay= 80 ms. Blocksize=64.
> *Pd 0.46.7 on Windows 7. *
>
>
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