ok i added the resistors and put a cut off frequency at about 16khz, clipping is gone and the spectrum of the sinewave is better. the sound output is far better, the sinewave is purer but noise remains the same... same crazy noise...
i tried with a factory made amplifier/speaker and it's the same, so it doesn't comes from my LM386 based amplifier circuit.
sorry about the lack of precision, i recorded the sound with the line input of an external soundcard.
jack out of the LM386 -> input line (soundcard). noise doesn't come from the recording process.
so i tested some simple triangle LFO like this and the result is good, less noise, it sweeps the frequency up to 8000hz (a record is joined):
cpt=cpt+(1direction);
if(cpt>8000)direction=-1;
else if(cpt==0)direction=1;
dfreq = (cpt10);
then i tested a code which triggerred some random notes with some linear interpolation to fill in between the notes and noise came back...
sweeping0hzupTo8000hz.wav (1.79 MB)