Hi. I just recently hooked up a mixer a friend gave me, which is in perfect condition and a brand new SM58. I'm running the SM58 directly into the mixer, and the mixer to my computer using two red and white rca cords into a 1/8 inch adaptor which goes into the "In" on my computer. However, I can't seem to get rid of a strange, fast pulsing noise that sounds similar to when you bring your cell phone to a set of speakers. I also am getting alot of hiss that i can't seem to get rid of. Any help?