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Loud background noise: cables picking up RF?

I have a significant background noise problem in my system. At normal listening levels, I am getting static that is audible from 15 feet away, and also a whistling sound coming through the speakers from time to time. I suspect that it is possible that my system is picking up some RF from the air, or that it is coming up through the electrical system. FWIW, around 2 miles from my house and 500 feet up, there is a broadcast array: 5 full-power FM towers, 2 NTSC full-powers, and some lower-power FM stations. A potential issue?

If this is the case, should I be going to a shielded-type IC? I get the noise as soon as my preamp and amp are engaged, whether or not I have a source hooked up. Can I buy a cheap AV-style IC from Best Buy and and see if the cables are the problem, or are those low-end IC's they sell really shielded? Are the power cords also a likely culprit? FWIW, I have

Any other ideas? I recently had my entire system checked up by the manufacturers, so all of the equipment is in good working order, but I can't seem to remove that background noise. Both my preamp and CDP are tubed, not sure if that is bad or not.
dawgcatching

Showing 4 responses by dcstep

dcstep
1,518 posts
 
Yes, you should use shielded ICs and go to balanced mode if you pre-amp allows. RFI and EMI can get into your system through IC, PCs, chassis, etc. Start with the ICs; however, you may have to move toward a balanced system.

Dave
dcstep
1,518 posts
 
You don't have to recognize the sounds for it to be RFI. A whistle, as described, can be an RFI issue. Usually it's just low level hash, but it can present as actual radio signals.

Of course, a whistle can be tube related also. I'd check all the tubes. Does the whistle come and go?

Dave
dcstep
1,518 posts
 
You've gotten lots of great advice here. Please follow up to let us know what you figure out.

If the ICs are a big help, then you're in one of those situations where almost every improvement you make will be noticeable. If that's the case, then I'd recommend going fully balanced if your pre-amp doesn't already allow it. Think of RFI with every IC and cord selection and consider putting a conditioner in the line. These improvements will be small relative to fixing your initial problem; however, when your bathed in RFI then plugging every hole is important.

Dave
dcstep
1,518 posts
 
Yes, speaker cables can be attennas, particularly when they are ribbons of wire with no criss-cross (rright-angle) geometry. Even short runs of parrallel wire ribbons can catch RFI.

Dave
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