[billyo]

i dont think its a power draw, when you plugged in your laptop using the usb, your default audio will become the usb audio codec, and when you plugged in your laptop, make sure you change the default audio setting of the laptop.. where in my case is the sigmal tel, the reason i think you lost the audio was because the laptop that you plugged into the channel input, revert back to the onboard soundcard.i think thats how these digtal board with usb works, i dont think you can plugged in anything with a built in soundcard unless you change the default audio setting..when i decided to used just input channel of the profx, my audio went out , i had to closed the program and i had to changed the default audio setting to sigmatel..( int. soundcard ), my way around it was to plugged in whatever you wanted to use ( usb or channel input ) before you t/on your laptop, this will automatically revert back to the int. s/card.