Surfing the most interesting "Describe your HIFI System" sub-forum, and based upon some pm's I received from it, it occurred to me many of us are encountering the same problem: 60Hz hum from connecting consumer gear to pro audio.
Consumer gear is not grounded - it persistently has only the two-pronged plug, fat on one ear (for polarity purposes). Hooking audio outs from a consumer preamp, amp, etc. to pro audio gear (EQ, amp, etc.) typically results in a nasty 60Hz hum. VERY simply speaking, that hum is caused by the consumer gear "seeing" another possible ground path, and trying to ground through the pro audio gear.
I use two solutions:
First, and best, is a DI - Direct Injection box. These have "ground lift" switches, which alleviate the problem.
Whirlwind makes a great stereo model (the Direct2) which has 1/4" unbalanced inputs/bypass and balanced Lo-Z XLR outs. The added benefit of the DI is it converts the connections to XLR, which all pro audio gear takes. Come out of the DI with a short mic cord into the pro gear. Go into the DI from your consumer gear with a lead that converts RCA's to 1/4" unbalanced. Monster Cable makes some nice (and pricy...) ones.
Checking the Whirlwind site yesterday, I found they're now offering a VERY nifty DI (the "pcDI") that accepts 3.5mm (1/8") mini TRS plug AND RCA's in TWO SEPERATE INPUT SIGNALS in one DI. So cool. The mini would connect your PC to the consumer gear, and whipe out that hum! As well, you can use the RCA's, too. Check it out: http://www.whirlwindusa.com/dirbox.html
Whirlwind by email confirmed that FirstAudioUsa (http://www.firstaudiousa.com/page1.html) is a reputable dealer (I Googled to them...). I ordered some through firstname.lastname@example.org who has an "eBayStore" that hosts competitively priced Whirlwind gear.
Second - and a nearly as good cheaper alternative - is an odd little lead that Radio Shack makes. The "Audio System Ground Loop Isolator" - Part No. 270-054 http://www.radioshack.com/product.as...5Fid=270%2D054
This uses inductive coupling for the audio signal, so the interconnected gear cannot seek ground across them. The lead is RCA-to-RCA, so may keep your wiring needs simple (for now...). There is slight signal loss, but it is not anathema to the solution.
Hope this helps.
email with questions