Alesis NanoPiano..hiss and white noise..

[CaveDweller]

I've owned an Alesis Nanosynth for years. No problems at all. I stumbled across a NanoPiano recently and bought it. Although I like the sounds from the unit....it emits a "white noise" or hiss constantly (even when volume is set to zero). It is not overly loud but is noticeable enough to make it unsuable for recording. My Nanosynth does not make this noise. Anybody else experience this from one of these modules? Not sure what the problem is. Any help or diagnosis tips appreciated. Cheers.