Noise with sound card

In playback with a sound card Edirol UA-4FX I have a problem of noise, kind of clipping as a saturation of the digital signal; But it does not saturate.
There must be an Audacity setting that I can not find.
thank you for helping me
In direct playback there is not this noise nor by exporting the audio files.
PLease HELP !!!

Mac Os-X 10.12, Edirol Ua4-fx
(sorry automatic translation from French)

Please see this FAQ: FAQ:Playback - Audacity Manual.