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Low-Frequency Artifact on narrow pulse width through amplitude envelope
Jan 04 2017 | 8:32 pm
I have uncovered something I don't understand. When I have the rect~ object hooked up to a *~ which is being driving by a metro+line~ or metro+adsr~ combo, and set the rect~ object to a narrow pulse width, there is a very low frequency thud each time the envelope re-triggers. Any idea why this is happening?? And idea's on how to prevent it???
It doesn't happen when rect~ is at 0.5 pulse width and doesn't seem to happen on the other basic waveforms. I am stumped because it seems to be something to do with the envelope and not the waveform itself.
- Jan 04 2017 | 10:38 pmHi Andrew purely subjective and naive answer here, but I think it is a combination of the amplitude envelope speed (causing amplitude modulation LF artefact) and the [svf~] emphasising that frequency. The ghost frequency isn't 'really' caused by the pulse width of the oscillator - I substituted a [phasor~] and the LF is still there. But its pitch is directly related to the frequency of the ampl env; therefore it's an AM artefact!HTH Brendan
- Jan 04 2017 | 10:40 pmPS [rect~] and [phasor~] are harmonically rich, compared to [cycle~], which is why the latter doesn't reveal the LF artefact. But I would hazard a guess that it is 'still there', just beyond human perception (until emphasised with a filter).
- Jan 04 2017 | 10:50 pm. . . . and, of course, you know that amplitude modulation, of even the purest tone will introduce sidebands:;)
