Loud background noise: cables picking up RF?
You don't have to recognize the sounds for it to be RFI.True. There are many forms of RFI. But with that said do you think if his problem is RFI, is it being caused from the communication towers? An arcing from a loose electrical power connection can also create RFI. And in many cases it can be heard in the form of a static sound.. Of course, a whistle can be tube related also.Also agree. But, what about the static sound heard 15' away? |
When is the noise present? Always ? With or without a signal present ? For all sources ? etc. Does the volume of the noise change with a change in the position of the volume control? The first thing I would do is find out what the noise looks like and what frequencies are present - audible and inaudible. Scope the various points in the signal chain to see where it is present and to see what it looks like. If you don't have a scope - buy one - Kenwood sells fairly inexpensive scopes new and you can probably pick up an old tecktronix cheap. Its not like you'll never have another use for it. 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. By seeing what it looks like and where it is you can do more than guess at it. |
Is everything plugged into the same electrical outlet? Also look at this - Jensen Transformer - it might be a ground loop and this will eliminate that. Of course it is best not to have anything at all in the signal path but you already have a major problem. |
Fully agree with dcstep's recommendations.You have to go for fully balanced system,using shielded and sielded IC.. You might also shield the unused RCA inputs usings specially made plugs{Cardas,Acoustic revive and the likes] Lastly if you use any type of ionizers make sure they do not fire directly to your preamp input. good Luck,and dcstep is right on the money |
