Puredata on raspberryPi with Usb sound card - distorted soun

[J__]

Hello,

So I successfully installed puredata on my raspberryPi, using the last verion of raspbian.

I run a test patch (osc~440 into dac~).
It works properly with the internal jack output.

I need to have an audio input, so I bought a Logitech Usb To 3.5 (referenced as a working soundcard).
It works properly with alsa player
aplay /usr/share/scratch/Media/Sounds/Vocals/Singer1.wav

But when running my test patch (nogui), I can hear the sinewave plus a constant distorted sound.

I tried a lot of options, dwc_otg.speed=1, etc. but I can't get it working properly.

Any of you have a usb soundcard properly with puredata?

Thanks for your advices,
J.