I keep my ep121 hooked up to pc speakers a lot of the time; when the computer is playing music or has any other sound-related job to do, this works fine, but left idle, the speakers hum. I would guess that this happens because the computer cuts power to the audio jack when it's not doing anything, and so the speakers hum just as though they were hooked up to a loose, powered chord. (It's the same sound you hear if you plug a cable into an amp without a guitar on the other end of it.) It ought to be possible to simply tell the computer to always run power to the audio jack when it's plugged in, but I can't figure out how this is done. Any thoughts out there? Best regards.