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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
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
jea48
4,504 posts
 
You are not hearing transmitted RF through your speakers - you cannot hear RF and your speakers cannot reproduce it - outside the frequency range for both.

His audio system can work like an antenna and receiver. And long speaker cables can work as an antenna and the transmitted RF will be heard through the speakers.
Example
You might want to check out the archives here on Agon.

I do think in the case of Dawgcatching if the sound he is hearing from his speakers is static, just my 2 cents, I don not think it is caused from the communication tower antennas. But no guarantees....

Static can also be caused from a HV cold solder joint or point on a circuit board with in the preamp or the power Amp. Could be a bad connection on a tube socket for example.

Unless Dawgcatching joins in the discussion it will be very hard to help diagnose the problem.
musicnoise
377 posts
 
No Jea48 you are incorrect - his speaker wire will not act as an antenna that causes transmitted RF to be heard through his speaker - that makes absolutely no sense - if that were the case he would be hearing RF all the time, with or without his amplifier on or connected. In every system on this planet the speaker wire is past the amplifier not before it.
dawgcatching OP
139 posts
 
Thanks for the advice. Describing the sound: I get a whistling sound when my CDP is engaged and I am on that input (probably some sort of DC leaking there) and a general hum when I turn the amp and preamp on together (not present when the amp only is activated). I am also getting a static background noise when I have my preamp hooked up (a Herron) but the preamp was just back at the factory and checked out fine. Perhaps it has something to do with the preamp tubes picking up something out of the air, although my backup preamp (EE Minimax, also tubed) isn't picking it up, and is much quieter.

The static is pretty constant: the whistling noise and hum comes and goes, although I usually hear the Whistling around 15 minutes into listening. It tends to diminish over time, but can still be heard at high volumes.

I should have posted this earlier: I am headed out on vacation on Monday, so I won't get time to start troubleshooting the system until I get back.
dawgcatching OP
139 posts
 
As far as the frequency scope goes, I will pick one up when I get back. The background static noise gets more audible as the volume increases: if I want to run my volume control to high listening levels (but not deafening) I can hear the static in the other room. The Hum level, however, is constant no matter the volume.
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