SO finally my UL310 arrives and I hook up the UL502 to get the juices flowing. I hear a low hiss with an underlying hum in the background. I call Epi, talk to one of the guys who says to lower the treble on my bass. (I never keep it up much) Do that but hiss and hum continue. They say to lower the tweeter control which is too sensitive. Well that cures the problem but then I'd have no tweeter. Anyone experience this low grade hissing or hum when not playing but the amp is on? Epi says this is normal noise but I won't hear it when I am playing live? Next odd problem. When I switch channels using the front panel buttons I get a quick "crack" or "static" sound when the button is pushed. When I press the mid-cut button the red mute light flicks for a second along with that same "crack" sound. Epi says to use compressed air and try and clean out the buttons because there might be dirt in them. (The amp is about a month old) C'mon I'm not stupid or an amateur. Before the 310 arrived I used headphones through the back and didn't hear any hiss, hum, or crack sounds at all. Anyone else notice these on their 502's or epi cabs or any combination of 502 & 310 together?