I get a noticeable hum on my sound input when using this set up: SM58 > X2U > USB port (of my MacBookPro). This is in my home not a studio. I notice that I can change the hum level with the mic orientation (like it's picking up ambient 60Hz). What now? Is there a shielded cable or grounding strategy to eliminate or minimize this effect?The customer wrote back with the resolution: "I resolved my noise issue. In my MacBookPro "sound" preference window on the input tab, I selected INTERNAL MICROPHONE and un-checked the "use ambient noise reduction" feature. The hum disappeared. Switched back to Shure X2u and smooth recording."