Shielding for FM tuner?

The problem with ferrite core clamp on filters is that they saturate with radio frequency energy very quickly, even the big fat ones, and once they do, they might as well not be there.

I'm tellin' ya, if you really want a quiet FM background, put floating shielded power cords on all your digital equipment (including CD transports) and if you want to use the ferrite filter somewhere, put it on the FM tuner's power cord, right where it enters the chassis.

Both your CDP (actually the DAC part, not the transport part) and your computer are putting out RFI (radio frequency interference) from their power cords, which act like transmitting antennas (even though the power cord may have a ferrite collar at the component end.)

To prevent this, you need to replace the regular 3 conductor power cords with ones that have a foil shield (and preferably, a braided shield as well.) The shield(s) must be "floated" from the component end. That means the shield(s) are connected (together with the green ground wire) to the ground pin of the AC plug end only, and not to the ground pin at the component end.

The good news -- that oughta do it. The bad news -- shielded cords with floating shields are hard to find at retail stores.

Unfortunately, you can't just run out and buy one at Best Buy or CompUSA because of what it costs big manufacturers to get a UL listing on such items. However, they're easy enough to make yourself by cutting off the IEC end of a commercial shielded cord and then re-terminating it with a new IEC connector but without the shield connected to it.

If you're not so inclined, many of the specialty manufacturers of audio power cords make them with floating shields in a variety of price ranges, and most of them are represented here on Agon.