To reduce the hum as Plank Spanker mentioned I plug directly into a wall outlet. No extension cords or power bars. That will kill quite a bit of the hum. If you are plugged into the wall then I would say there is some issues.
I have a 2008 DSL100 and it has a slight hum. I went to premium guitar cables and that helps a lot. But the biggest issue for me was the power.
I purchased a pedal board with a conditioned power supply and that makes all the difference.
One day my wife unplugged it to clean and plugged it into a power bar that I had for my TV and Stereo.
I picked up this loud hum and thought one of my pedals was fried. It took me a whole day of testing each pedal, to finally find the main plug for the board plugged into the power bar. It was behind a couch. I plugged it into the wall and it was dead quiet.
Hope that helps.