I recently got a Rega Fono Mini A2D for digitizing LPs, which I'm using with a MacBook and Audacity. I'm just plugging the turntable directly into the Rega with a USB cable going into the laptop. However, I'm getting a higher-pitched hissing sound, and turning the level knob on the Rega unit has no effect on the level of it, except to change the pitch of the hissing. When listening back to the digital files, it's audible in quiet sections, like when a song is nearing the end of a fade out, or in between tracks, for example. The Rega sounds fine and quiet when plugged into the Aux of my receiver, so it seems like something is up with the USB out, or perhaps it's something with Audacity? The weird thing I'm noticing about Audacity is that it's not letting me adjust the input volume - when I switch the Recoring Device to USB Audio Codec, the input volume slider defaults to the maximum volume and can't be moved. Not sure if this is adding noise that would otherwise be inaudible if I could lower the input volume? Is the Rega A/D just noisy? Or could this be something else? I'd appreciate anyone's input on this.