Radio(?) interference in monitors???

[sporkles]

OK, so I've just moved into a new house, and I've set up my system, but when I flicked on my monitors (Behringer Truths, active), I got this low-level, distorted radio signal coming through (Adele, whoopee-whooo!). Having overcome the urge to primal scream, I tried all I could think of: I plugged the monitors into different sockets, I unplugged the audio cables, but no dice: the noise is still there. Is there some kind of device I can insert between the power strip and the mains to overcome this?

Our house has cable TV, and this struck me as a possible culprit. I don't know?

[infernal.machine]

You're getting radio when there aren't any cables (besides power of course) plugged into your monitors? My first guess was badly insulated audio cables, but if this is true I don't know...

Interested in hearing other responses.

[sporkles]

I did some searching, and it seems like the monitors' power cords can act as a kind of antennae, and that there indeed is such a thing as an "RFI filter". The question is whether or I need one for each monitor, or if I can place one before my power strip (I use a dedicated power strip for my monitors so that I don't have to switch them on/off one by one).

[jbodango]

are you using balanced cables?

[jestermgee]

are you using balanced cables?

N/A because it happens without anything plugged into monitors.

I have had to deal with all manner of interference from AC hum to PC and video monitor induced noise and almost all of the issues come down to earthing.

Firstly a WARNING if you have no clue whet you are doing, find someone who does or just don't attempt it. It's a risk suggesting tests to people that may not have an understanding but I can understand the frustrations.

To test out earthing issues I have a power board I use without an earth pin. This is NOT actually used full time it is just for testing to create a system that is disconnected from earth. You could use something like this (if your monitors have earth connections) to test your earthing.

In your case you seem to have interference without any audio cables connected so there are really only 2 places this can be getting into your monitors:
1. Air Waves: If you have actual radio signals and slight audible audio from your monitors it could be induced into the amp circuit directly via airwave. This is very unlikely unless the transmission source is very close but it could be compounded by the earth connection acting as an antenna which will run through the entire building.

2. Through the AC lines. Some devices can create noise directly on the active and neutral lines of the AC. This should rarely occur but can in some cases.

Poor earth connection including physically the earth stake itself can prevent any proper grounding of a system and allow any interference to build up and travel between devices.

One test is to float the system and not allow anything to have a path outside the system. Plug in your monitors to the unearthed power board directly. If it clears up the issue you may have an issuue with earthing in your place. I would suggest getting that tested as you may find you not only have a poor earth but voltages could potentially flow through the earth from one device to another if they do not have a path to ground. This is the BIG issue if you remove the earth pin on devices.

You can test earthing yourself if you know what you are doing but I won't explain how to test the earthing because if you have a crook earth and create a different earth path and connect the 2 together you can run the risk of voltages being drawn up 1 earth and through to the other which is why a single system should only ever have a single earth point.

[sporkles]

Ok; here's a little update: having done all the testing I could think of, including plugging one of the monitors into an ungrounded outlet with no change, I started experimenting with tin foil. Yes. I wrapped my one monitor and its power cable in aluminium foil, and could hear a significant improvement. I decided to take it a step further and popped off the back panel on the monitor and put the foil in between the cover and the circuit board. I was absolutely amazed when I flipped the speaker back on afterwards; the radio signal was gone.

I went ahead and tried the same thing with the second monitor, but I couldn't immediately reproduce the great result. I guess I'll have to pop it open again and see if even more foil will help.

[fishmonkey]

you wanna be a bit careful sticking foil in there, since it's conductive...

[Dewi32]

sounds like a ground loop issue for sure. this will fix it.

http://www.amazon.co.uk/Behringer-MICRO ... B000KUD2G4