okay i tried your suggestion.
reducing the wavetable amplitude to 0.8 instead of 1 changed nothing.
but it isn't a clipping problem.
no nonlinea frequencies are added.
The signal only consists of the right harmonic overtones
setting the phase increment to an integer value solves the problem.
but it has the drawback that i can't hit exact frequencies anymore.
for example with a table size of 512 samples and 44100kHz SR
when i use a phase increment of 5 i get 44.1kHz / 512 * 5 = 430.66 Hz
the next phase inc. 6 would give 44.1kHz / 512*6 = 516,79 Hz
everything in between is inaccessible. so no 440Hz possible.
adding linear or cubic interpolation makes it a little better, but the
pulsing is still very audible.
but it has definitely to do with the phase wrap. The nearer i get to an
integer phase increment, the slower the amplitude of the harmonics is
pulsating. at an integer value it stops.
what is the correct way to implement the wavetable osc to stop the
overtone pulsing without using huuuuge wavetables?
julian
Am 09.04.2012 17:38, schrieb Olli Niemitalo:
If you don't interpolate the wavetable then you may be simply getting
some aliasing problems. Every Nth cycle of the generated waveform will
be one sample shorter than the others, and that will sound like a
click. Try setting your phaseInc to an integer value. Also, somewhere
along the analog signal chain you may be getting nonlinearities with
the Gibbs phenomenon peaks if you are running your wavetable
oscillator at full-scale amplitude. Try reducing the wavetable
amplitude.
-olli
On Mon, Apr 9, 2012 at 4:28 PM, Julian Schmidt
<julian_schm...@chipmusik.de> wrote:
phase += phaseInc(440); // calculate the phase increment for 440 hz and add
it to phase
if(phase>= TABLESIZE) phase -= TABLESIZE;
return phase/TABLESIZE;
[...] My problem is that i get periodic amplitude modulations on the overtones
about 2-3 times a second.
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