[pjchappy]

Well, I've touched on the problems I have been having with RFI briefly in some other threads.  I want to tackle the issue separately.

I am having problems with RFI with my guitar amp and my microphone preamp.  I keep picking up an AM radio station in both.  Also, the amp sometimes picks up a weird repeating clicking signal, which I can somewhat alleviate by rotating the amp. 

I recently added a TrippLite IsoBar to the mix.  I have only been able to try it with the guitar amp and not the microphone preamp yet.  When trying the amp, I also used brand new homemade guitar cables (Canare StarQuad and Canare GS-6.  On a side-note, the StarQuad is pretty microphonic.  )  The RFI improved, but I can't say for sure if it was the cables or the IsoBar that had anything to do with it. . .or both.  (I'll experiment with that this weekend).

As for my guitar amp, the RFI increases when I use my pedal board, likely due to more of an antenna effect.  I plan on making all new patch cables for the pedal board, using the aforementioned Canare GS-6.  The GS-6 is a single core coax cable made specifically for music equipment use.  It has a copper shield, used for the return signal, in addition to a thin, conductive carbon shield.  Specs here: http://www.canare.com/ProductItemDisplay.aspx?productItemID=61  I'm willing to try just about anything. . .so, I also will be replacing the pedal board's power cord with a Volex shielded cord and the amp's speaker wiring with some wiring I have laying around.

Any other suggestions?  Why would I have this much RFI?  Someone suggested I check the amp's and pre-amp's cabling, etc. for miswired grounding.  However, I have tried numerous cables on the guitar amp.  I have also tried three different XLR cables on the microphone preamp. . .and on both of its inputs.  I have also used another microphone preamp and tried both of its inputs and have the same problem.  So, doesn't look like its a wiring/grounding issue.

I do not live near a transmission tower.  Not sure if it makes a difference, but I live in a bit of valley.  Why am I getting so much RFI? 

Thanks,


Paul

[Speedskater]

Jim Brown of Audio Systems Group has several papers on the problem:

http://www.audiosystemsgroup.com/publish.htm

Not only is Mr. Brown a leading authority on audio wiring, he is also a HAM radio operator.

[Niteshade]

Small capacitors across the inputs might help. They have to be installed within the amplifier behind the sockets or right on the board. Try something like 200pf caps. If your inputs are balanced, use two caps per input to tie each leg to ground through the cap.