My PD version is 0.42.5, It worked fine until yesterday. The problem is indicated as below:
I put a single oscillator (osc~ or cos~) and linked to dac~. Turn on the DSP and it starts making a high pitch noise sinewave like noise even the input frequency is set to 0Hz. If I modulate the frequency and the amplitude, the background noise seems to be modulated as well.
I did the testtone and it appears to be normal with no noise.
All the best.