It goes away a little when I touch the strings, the amp works fine though
I see this thread has been up for a while, so I don't know if you found the problem yet or not - but, that sound like it could be an AC outlet problem.
Check the AC outlet and try a different AC outlet - also try another guitar cord too.
http://www.amazon.com/Electrical-Re...TF8&qid=1385916911&sr=8-3&keywords=AC+Checker
EDIT: Oh, or it could be bad shielding or a bad ground on you bass - check the ground wire under the bridge and or try another bass too.
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