sounds like you may need a 3pin to 2pin AC adapter. that's what fixed the hummmmm for me,

Ground Loop Isolator from Radio Shack did the trick. www.radioshack.com $17

Wait wait wait. Can you confirm, that without the adapter, and just your computer connected to the mixer you can hear this hum? Please this is pretty important to me. Lifting the ground (thats what the 3->2 pin adapter does) is not a good (and secure) way to fix this.

Definitely nik. I use my PC's sound card & speakers for my monitors, recording, etc. and as soon as the 57 enters the equation the ground loop hum appears. A quick search around the net found that this is common when connecting audio equipment to a PC. The isolator fixed the problem instantly.

Well, it didnt happen for me when using the TTM56 and the SL1! I will ask some moderator to comment on this issue. Thanks.

TC, another question, is this just a low frequency noise or also some higher pitched noise?

All low freq. hum. The exact hum you would get if your 1200's weren't grounding or headshell grounds / connections were dodgy.

Hm, okay then I am having a different issue. Dang.

Just to make sure you and everyone else is clear on this: the Ground Loop Isolator that Thundercat installed is *not* a ground-lifter...it's actually a pair of audio transformers that go in-line between pieces of equipment. No safety issues there.

The only issue is that the transformers Radio Shack uses in that device aren't of the greatest quality, so (especially if high levels are fed through them) the sound quality can be affected by using them. Better-quality transformers are made by companies like Jensen, and this model www.jensen-transformers.com would give much better audio performance than the Radio Shack product (although the price is about ten times higher).

I dont like radio shack cables; they peel off seperately like those pull n peel Twizzlers